A brief overview of the last campaign of Chingiz Khan and the issue of succession in the Mongol empire

Succession is always an important issue in history. The legacy of a mighty ruler and/or founder of an empire might quickly unravel if the issue of succession is left unresolved. In Hindu history the Gupta-s were marked with glory because following Candragupta-I they managed to maintain a line of highly successful rulers with relatively smooth succession: Samudragupta-> Candragupta-II Vikramāditya-> Kumāragupta-> Skandagupta->Budhagupta. Before them, the Maurya-s had several succession problems but managed to put out a line three mighty rulers. However, sometime during the reign of Aśoka things started going bad and they never able to produce one within their own line who could restore their power. In the case of the house of Śivajī, many of the troubles for the fledgling neo-Hindu empire came as a result of problems with succession. Among the Hindus, primogeniture meant that Śivajī’s eldest son Śambhu would ascend the throne. However, he had shown bad behavior and betrayed the cause of svarājya about a couple of years before the great rajan’s death. Hence, he had been kept under detention at the Panhala fort and some of Śivajī’s veteran ministers Moro Piṇgaḷe and Aāji Datto had turned against him. His stepmother was trying to place her young son Rājārāma on the throne. The ensuing conflict seriously damaged svarājya at a critical juncture in the struggle of the Hindus against the Mohammedans. Chingiz Khan faced a parallel situation of indiscipline and possible disloyalty from this eldest son. His eldest son Jochi was born shortly after he recovered his wife Börte who in captivity of his enemies for few months. A conflict broke out between Jochi and his brother Chagadai and given the timing of his birth his legitimacy as the son of Chingiz was called into question. A council was called and Chingiz and his generals like Chormagun Noyan worked on patching up the issue between his sons. While his father declared him to be a legitimate son to the rest of his sons, the tensions persisted and towards the end of his life he remained away in own ulus disobeying his father’s orders when called to meet him. It appears that the great Khan might have sent his sons Chagadai and Ögödei to bring Jochi to him to be disciplined. The tensions ensuing from this could have affected the succession issue but two factors played a role in resolving it. First, among Altaic peoples ultimogeniture was the generally accepted rule unless it was overruled by some clause of the previous Khan. Second, Jochi died shortly before Chagadai and Ögödei set out to bring him to the Khan, thus taking him out of the contention for succession. But that aside, the success of the Mongol empire was in part how the succession to Chingiz Khan was handled.

In 1223 CE, shortly after Jebe and Sübe’edei had crushed the combined army of the Russians and Qipchak Khanate on the Kalka River, Chingiz Khan in a council of senior Mongol commanders and officials declared that Ögödei would succeed him as the great Khan. In making his choice he considered the following: His first son Jochi was a competent general who had distinguished himself early in his career in the Siberian conquests, in the annexation of the Kirghiz horde, and later during the attack on the Mohammedans while seizing the fortified settlements of Signakhi, Yanikand (the capital of Oghuz Turks) and Jand. However, during the siege of Urgench, his strategy and pace of the campaign were criticized by his brothers Chagadai and Ögödei. Finally, it was Ögödei who stormed the city though it was promised already by the great Khan to Jochi. This was followed by his conflict with Chagadai during which his legitimacy as the son of the Khan was doubted. He restored his military credentials by aiding Sübe’edei after the death of Jebe. However, after this, he disobeyed his father and retired to his ulus and never met him again. Thus, he was ruled out. Chagadai, the next son, was also a competent warrior; however, his quarrels with Jochi, his temper, and recklessness in the quriltai-s did not please the Khan. Hence, he too was passed over for being the great Khan.

The next son Ögödei was seen as a man of balanced temper but at the same time a fierce warrior who proved himself in the thick of battle. When in his early years Chingiz fought the alliance of Jamuqa and Toghrul Wang Khan of the Kerait Turks, Ögödei, still in his teens, was seriously injured by an arrow that hit his neck. He was then saved by Chingiz’s foster-brother Boroqul. Surviving this injury, he led the Mongol forces again the Jin (Jürchen) to conquer the city of Ordos in Inner Mongolia. In the campaign against the Mohammedans of Khwarizm, he along with Chagadai seized the fortified city of Utrar and then took Urgench. In Afghanistan, he smashed the Mohammedans of Ghazni and massacred them (truly their karma was being paid). Thus, Chingiz Khan chose Ögödei as his preferred successor to the post of the great Khan of the unified empire. At the same time, the other sons were to get their own ulus-es. They were to hold a quriltai to confirm if Ögödei was competent and if members from each of the lines elected him then he could ascend as the great Khan, with all of them pledging their solidarity to him. In the interim, the default state of Altaic ultimogeniture was to come into play with Chingiz’s last son Tolui serving as acting Khan until the quriltai could be called. This tradition of ultimogeniture appears to have been adopted by the Altaic peoples from the steppe Iranians who were the lords of the land before them. Keeping with the old tradition of ultimogeniture the Khan’s youngest son Tolui was awarded the biggest share in the Khan’s personal inheritance. This also included the largest share of the military which eventually allowed the ascendancy of his lineage.

To take a look at the succession as it happened we shall briefly revisit the final years of Chingiz Khan. When Chingiz Khan left to campaign against the Mohammedans, his Chinese campaign had to proceed at a slow pace as most of his forces were deployed in the west. He had left his friend from youth and able general Muqali to conduct this campaign against the Jin. Muqali with his limited forces managed to preserve to Mongol conquests in China and also keep the Jin on their feet with regular raids into their territory. Then he conducted an audacious campaign with his small Mongol forces by launching an invasion of the Wei River valley at the southern bend of the Yellow River. Thus, he kept the pressure on the Jin till his death in 1223 CE. Then his son Boro and grandson Tash continued the campaign against the Jin. They expanded the campaigns to attack the Han Chinese empire of the Song who came to aid the Jin. However, with their limited army, they could in no way conquer these vast domains completely. In 1225 CE, having smashed the Mohammedans of Khwarizm, Chingiz Khan returned to Mongolia to review the Chinese situation.

Around the time of Muqali’s death, the Tangut of Xixia empire got a new aggressive emperor Li Dewang. He decided to launch a massive attack on his old enemies, the Mongols. For this, he formed an alliance with the Jin and also mobilized the Yellow Uighurs against the Mongols. The Mongol generals Boro and Tash staved off the immediate attacks till Chingiz Khan returned. The Khan strategized that to conquer the vast realm of China he had to first outflank the two Eastern Chinese empires from the west by destroying the smaller western empire of the Xixia. The Tangut expected him to stiffen Muqali’s successors by marching from the east but the Khan surprised them by assembling a large Mongol force to the west and attacking them from Gansu corridor in 1225 CE. The great Khan marched with close to 120000 men with the largest division of several tümen-s (~80000) personally led by him, with the rest led by his brother Qasar whose health was declining due to gout, the ace general Sübe’edei baghatur, and the general Chaga’an. Sübe’edei first crushed the Yellow Uighurs and took them out of their way. Chingiz Khan directed him to systematically conquer the western towns of the empire and facilitate the penetration by Chingiz and Qasar deep into the Xixia territory. Taking their old capital, Qara-Qoto, the Khan steadily advanced eastwards and by August of 1226 CE despite fierce resistance from the Tangut aided by the Jin from the East the Khan forced their second largest city, Wuwei to surrender.

At this point, Li Dewang died and Li Xian ascended the throne as the emperor. Li Xian claimed he was the Buddha of the Age but that did not seem to help much. Advancing further Chingiz Khan then besieged the fort of Lingwu which was just a short distance from the capital Yinchuan. Li Xian sent a massive army of 300000 Tanguts hoping that he could comprehensively overwhelm the Mongol army. But in the battle fought on the banks of the Yellow River the outnumbered Mongol forces under the inspired leadership of the great Khan nearly completely annihilated this Tangut army in November of 1226 CE. In 1227 CE the Mongol army besieged Yinchuan the capital of the Tangut. The Jin tried to help the Xixia empire survive by sending aid from the east. But Chingiz Khan sent his mobile squadrons to punish them. One rapidly moving Mongol force launched an audacious assault deep into Jin territory to strike their capital Kaifeng and return. Shaken by this attack, the Jin asked for peace but Chingiz turned down the offer and already prepared an invasionary force to next deal with the Jin. However, as the siege of Yinchuan was drawing to a close the Khan fell from his horse evidently during a hunt and probably sustained an injury that resulted in an infection. Others believe that he might have contracted some infection independently of a fall. He was taken in a closed bullock cart to a secret hideout the Mongols set up in the forests of the Liupan mountains. He realized he was on his deathbed and called his clansmen and generals around him. He gave them a final lecture in which he laid out the lines of action to expand the Mongol empire he had founded both to the east and west. He then stressed the issue of unity between the different lines of his clansmen with the famous example of the single arrow and bundle of arrows. He asked his people to follow his plan regard his successor and told them: “Let not my end disarm you, and on no account weep or long for me.” Before dying he also seems to have made his long-term succession plans clear. The status of the great Khan was not to remain with the house of Ögödei forever. He said that his grandson through Tolui, the wise Qubilai, would someday adorn his throne. Then he died aged something between 65 to 70 on either on 18th or 25th August 1227 CE as per different reckonings.

The Mongols kept the news secret and his youngest son Tolui became the acting Khan to allow the campaign to proceed. In September 1227 CE Li Xian unable to hold the capital surrendered to the Mongols. They had is name changed from the Buddha of the Age to Shidurgu – the one who has been made a vassal. Thus, having stripped him of his divinity they immediately executed him as a treacherous vassal. Then they erased the city of Yinchuan with its citizens except for the bauddha teachers of the Karma Kagyu tradition and their monastery. The Mongols demolished and dug up all the graves of the Tangut emperors and dispersed their remains. The Tangut had ties with the Pāla and Sena dynasties of Vaṇga before the devastation of their land by the Mohammedans. Thus, several of Li Xian’s surviving relatives fled towards Vaṇga but with the ongoing Mohammedan depredations throughout the region, they settled in the more inaccessible domain of Sikkim.

Over the year 1228 CE, Tolui assembled members of all the branches of the house of Chingiz for a quriltai. Before they joined in Mongolia, a quick campaign was conducted in the west beyond the banks of the Volga pulverize and subjugate the Volga Bulgars who had staved off the earlier raid of the Mongols during their attack on the Russians and the Qipchak Khanate. The quriltai met at Köde’e Island on the Kerülen River in Mongolia. There the majority of the lines voted in favor of Ögödei becoming the next great Khan and his brother Tolui dutifully handed over the throne to him. Jochi’s most prominent son Batu also pledged complete solidarity to his uncle. Thus, the unity of the Mongol empire was retained under Ögödei and he ascended the throne taking on the title of Dalai-yin Khan. This title was likely semantically equivalent to Chingiz Khan and means the oceanic ruler. A derivative of it was later also conferred by the Mongols to the chief Lama – the Dalai-lama. It is likely that this event was marked by the production of the famous seal bearing the words:
Möngke Tengri-yin Küchün-tür Yeke Monggol Ulus-un Dalai-yin Khan-u jarligh il bulqa irgen- tür kürbesü büsiretügüi ayutughai
By the Power of great god of heaven, the Edict of the oceanic Khan of the Great Mongol ulus. If this reaches a pacified or a rebellious people, it must respect [it] [and] it must fear (Text and Translation from Igor de Rachwiltz).

He immediately commissioned what become the core of the Secret History based on the records kept by Shigi-qutuqu, the adopted son of Chingiz Khan. It is not entirely clear if Shigi-qutuku also wrote the core of the Secret History. The phrase “khan ecige minu” meaning “khan, father of mine” is seen occasionally in the text suggesting that it might have been him. However, some historians think that in general Chingiz was referred to as the father of the Mongol nation at some point during the redaction of the text (Today there is evidence for some biological basis for that).

Ögödei immediately got around to stabilizing the newly won empire. As per the wishes of his brother Tolui he appointed Sübe’edei Baghatur as the supreme military adviser of the Mongol empire. This brilliant general had campaigned across the whole of Eurasia and was beyond doubt one of the greatest military leaders of all times. Tolui was given the title Yeke-noyan (some say the yeke was added after his death) meaning the great lord and advised the great Khan on all matters. Chormagun noyan was appointed to lead a Mongol army to finish off immediate unsettled issues in the west like the destruction of Jalal-al din and conquering Armenia, Georgia, Chechnya, and Azerbaijan. Shigi-qutuqu was appointed to handle the implementation of the yasa of Chingiz Khan and set up the administrative structure for the whole empire. The gigantic Khitan (an earlier branch of Mongolic people) scholar Yelü Chucai had been brought out from his early retirement as a Zen bauddha monk by Chingiz Khan and appointed to his advisory council, especially for his meteorological knowledge. He was left back by the Mongols after the campaigns in the West to organize their rule there. It was then that Yelü Chucai obtained an Indian rhinoceros and showed it to the Mongols (The śākya buddha had in a former birth seen a rhinoceros directly attain buddhatva). The Mongols declared that the animal was a sign of the great god Möngke Tengri and that India should not be invaded as it was the holy land graced by this divine animal. This gave him a great aura of respectability and he was called by the great Khan to help him with the administration in the last year of his life. Tolui while the acting Khan asked Yelü Chucai settle the major religious conflicts which were taking place between bauddha-s and Taoists in Mongol China. He also actively participated in getting everyone to agree on electing Ögödei and was accordingly rewarded by Ögödei with an appointment as the supreme official of the revenue department of the Mongol empire.

An important point that is often not stated is the role of Ögödei in stabilizing the Mongol empire. At Chingiz Khan’s death treasury was in precarious condition. The Khan had put everything into the Xixia campaign. Temporarily the situation was stable from the enormous booty obtained with the destruction of Xixia empire and the raids on the Jin. However, Ögödei needed to quickly stabilize things for the long term before further major campaigns could be undertaken. Hence, he constituted a senior council drawn from the keshikten (the Khan’s inner guard) along with Yelü Chucai to develop a comprehensive taxation system across all conquered territories with revenues assessed as per the nature of productivity of each territory. A whole series of Mongol and local officials were raised and the system put in place throughout the vast empire within a matter of four to five years. This went hand-in-hand with a courier system to allow communications throughout the empire. This administrative achievement pulled off by Ögödei is probably the most underrated but important facet of the development of the Mongol empire. Beyond that, he also was proactive in his diplomacy to get the houses of all his brothers to stand firmly with him and cooperate as part of the unified Mongol empire for future campaigns.

Thus, key aspects of the success of the Mongol Empire were Chingiz Khan’s clear succession plans, their orderly and quick enactment, and finally the successor Ögödei’s effective administrative action. He first settled and firmed up fiscal and organizational issues of the empire in great detail before launching the next major phase of distant military activity. As this was under way he commissioned the campaigns under Chormagun Noyan to create the strategic base for big distant ones which were to follow. Only thereafter the great invasion of the lands of the White Christians in Europe and the mopping up of the Jin empire in China were launched. It is in comparison to this that the Maraṭhā succession was rather poorly executed. Though Śambhu took power rather quickly, it came at the cost of the brutal execution of senior ministers like Annājī Datto. He also was hardly effective in terms attending to fiscal, administrative and strategic issues. While his early campaigns were well-executed were not followed up with the vigor and swiftness his father showed. When Ögödei was facing doubts in how the Chinese campaign should proceed his senior strategist Sübe’edei showed the way forward and led them to spectacular victories. Śambhu however showed little interest in supporting his astute military adviser Hambirrāv Mohite‘s plans at a critical juncture. These considerably strained the Maraṭhā-s and they eventually survived only due to Śivajī’s farsighted plans and ministers like Rāmacandra amātya.

Posted in History | Tagged , , , , , , , , ,

The mean hyperbola and other mean functions

Let a, b be two numbers such that,
0\le a \le b
We use a, b to construct a specific rectangular hyperbola using one of the following methods:
Method-I (Figure 1: this is based on an approach we described earlier)

hyperbola_constr_mean2Figure 1

1) Mark point C (-a, a), which will be the center of the hyperbola to be constructed.
2) Draw two perpendicular lines through C respectively parallel to the x- and y-axes. These two lines are the asymptotes of the hyperbola.
3) Bisect the angle between these asymptotes to construct a line with slope m=1 passing through C.
4) On this line mark the two foci of the hyperbola F_1, F_2, such that they are are equidistant from C and separated from each other by a distance of 4\sqrt{ab-a^2}.
5) With F_1 as center draw a circle with radius equal to 2\sqrt{2(ab-a^2)}. This will be equal to the distance between the two vertices of the hyperbola.
6) Let Q be a point on the above circle. Draw lines \overleftrightarrow{F_1Q}, \overleftrightarrow{F_2Q}.
7) Draw the perpendicular bisector line of \overline{QF_2}. It cuts \overleftrightarrow{F_1Q} at point P.
8) The locus of P as Q moves on its circle gives you the required rectangular hyperbola (red in Figure 1).

Method-II (Figure 2)

hyperbola_constr_mean

Figure 2

1) Mark point C (-a, a), which will be the center of the hyperbola to be constructed.
2) Draw two perpendicular lines through C respectively parallel to the x- and y-axes. These two lines are the asymptotes of the hyperbola.
3) Bisect the angle between these asymptotes to construct two perpendicular lines with slope m= \pm 1 passing through C.
4) On the line with slope m=1 mark the two foci of the hyperbola F_1, F_2, such that they are are equidistant from C and separated from each other by a distance of 4\sqrt{ab-a^2}.
5) On the line with slope m=-1 mark a sequence of points and draw a sequence of coaxial circles, which will pass through each of those points on this line and also the two foci F_1, F_2.
6) Each of these circles will cut the two asymptotes on total of 4 points. On each side separately draw segments joining the respective points of intersection of each circle on the two asymptotes (Figure 2).
7) The envelope of these segments is the desired hyperbola.

The said hyperbola has the equation:
y=\dfrac{a(x+b)}{x+a}

hyperbola_meanFigure 3

One observes that its upper branch cuts the y-axis at (0,b) and by construction it is asymptotic to x=-a, y=a (Green curve in Figure 3). But what else notable about this specific hyperbola? Note the intersections of the following lines with the hyperbola (Figure 3):
The line x=a intersects the hyperbola at y=\mu_A, the arithmetic mean of a,b.
The line x=b intersects the hyperbola at y=\mu_H, the harmonic mean of a,b.
The line x=y intersects the hyperbola at y=\mu_G, the geometric mean of a,b.

Thus, this hyperbola can be considered a mean-generating curve where the means of the two numbers a,b can be easily obtained by plugging certain nice values of x. It also furnishes the proof for the fact that the three primary means of two numbers lie on a single hyperbola between the point where the hyperbola cuts the y-axis, point B(0,b) and the asymptotic line passing through A(0,a). One notices that the \mu_A cuts the segment \overline{AB} in half. The geometric mean \mu_G cuts \overline{AB} below \mu_A and the harmonic mean \mu_H cuts it below \mu_G. This geometry allows one to define two further means, which are inversions (reflections) of \mu_G and \mu_H respectively on the \mu_A line. We define these inversive means as \mu_{Gi} and \mu_{Hi}. We discover that the intersection of the line x=\tfrac{a^{3/2}}{\sqrt{b}} with the hyperbola generates y= \mu_{Gi} = \tfrac{a^{3/2}+b^{3/2}}{\sqrt{a}+\sqrt{b}}. Likewise, the intersection of x=\tfrac{a^2}{b} with the hyperbola generates y=\mu_{Hi}=\tfrac{a^2+b^2}{a+b}. Thus, we have 5 means with the arithmetic mean as the central mean bisecting the segment \overline{AB} with two means above it and two means below it (Figure 3).
In trying to understand these additional means coming from our hyperbola we learned of the work in this regard by Derrick Lehmer-II. He defined two mean generating functions. The first of them is (orange in Figure 3):

y=\dfrac{a^{x+1}+b^{x+1}}{a^x+b^x}

We notice that this function is a sigmoid curve having y=a and y=b as its asymptotes (Figure 3). We realized that this function of Lehmer generates the same means as the above-constructed hyperbola. When x=0 we get \mu_A; when x=-\tfrac{1}{2} we get \mu_G; when x=-1 we get \mu_H. The two other means \mu_{Gi} and \mu_{Hi} respectively emerge at x=\tfrac{1}{2} and x=1. Thus, the same symmetry as the with the hyperbola is recapitulated by this function (Figure 3).

Lehmer’s second mean-generating function is (red curve in Figure 3):

y= \left(\dfrac{a^x+b^x}{2}\right)^{\frac{1}{x}}

We observe that this curve is also bounded by the same asymptotes y=a and y=b; however, it converges to them at very different rate. At x=1 it generates \mu_A; at x=-1 we get \mu_H and it intersects the first mean-generating curve (Figure 3). At x=2 we get the \mu_Q, i.e. the quadratic mean or the root mean squared (RMS). This mean cannot be obtained by a nice value of x in either the first mean-generating function or the mean hyperbola. What about the value of the second mean-generating curve at x=0? To get that we need to do is to evaluate the below limit:

\displaystyle \lim_{x \to 0} \left(\dfrac{a^x+b^x}{2}\right)^{\frac{1}{x}}

At first sight, it would seem that it is indeterminate because we get an ugly division by zero making it impossible to evaluate directly. Hence, this cannot be done and we have to take recourse to Johann Bernoulli’s method (commonly called L’Hospital’s method).

We first take the logarithm of the above expression to get:
\dfrac{\log\left(\dfrac{ (a^x + b^x)}{2}\right)}{x}

Then we differentiate the numerator and the denominator. The denominator is reduced as \tfrac{d}{dx}x=1. For the numerator we get:

\dfrac{d}{dx}\left(\log\left(\dfrac{ (a^x + b^x)}{2}\right)\right) = \dfrac{a^x \log(a) + b^x \log(b)}{a^x + b^x}.

We next take the \lim {x \to 0} to get \log\left( \sqrt{ab}\right). We then reverse the logarithm operation by exponentiation and evaluate the limit of the second mean-generating function at x=0 to be \sqrt{ab}. Thus, Lehmer’s second mean-generating function yields the geometric mean at x=0. Lehmer showed that there are thus two families of means of which one includes the inversions of the geometric and harmonic means on the arithmetic mean and the other which includes the quadratic mean or RMS. The only means that are common to both families are \mu_A, \mu_G, \mu_H and the two mean generating curves intersect at y=\mu_H (Figure 3). Thus, these 3 are the only fundamental means.

While these two families of means do not come together is there an operation where combining a fundamental and family-specific mean gives an interesting result:

Let a_0=1, b_0=1 and n \in \mathbb{N},
a_{i+1}=(\mu_Q(a_i, b_i\cdot \sqrt{n}))^2
b_{i+1}=(\mu_G(a_i, b_i))^2

Then \dfrac{a_{i+1}}{b_{i+1}} \to \sqrt{n}
This gives us a means of obtaining rational convergents for a given irrational square root. For example if we use n=6 in the above procedure we get:

\dfrac{7}{2}, \dfrac{73}{28}, \dfrac{10033}{4088}, \dfrac{200931553}{82029808}, \dfrac{2523338293565406}{1030148544608239}

The last of these yields \sqrt{6} correct to 11 places after the decimal point.

Also see:
1) Means and conics
2) The Hindu square root method

Posted in Scientific ramblings | Tagged , , , , , , , , , , , , ,

A Political roundup August 15 2018

As I remarked to a friend, much of the stuff in (geo)politics which is relevant to us is what we have predicted before based on the relatively straightforward model of mleccha-marūnmattābhisaṃdhi i.e. the anti-heathen coalition of those infected by Abrahamistic meme-plexes and their secular mutations. What remains is just too uncertain to predict with our limited knowledge and ability. This might be the more interesting and perhaps the more dangerous part of our existence, but for most part we simply have to watch it unfold. That is part of the reason why we are not too motivated to write a lot about this on these pages. Nevertheless, we felt it might be appropriate to provide review of for another Independence Day has dawned and given that the elections are scheduled for next year.

So let us take a panoramic view by traveling back in time. The great demolition at Ayodhya on 6 December 1992 was a landmark even that hinted that the Hindus were no longer going to take things lying down. hence, we call upon fellow Hindus to observe a moment of remembrance for the men who gave up their lives to bring down that symbol of marūnmatta tyranny. This event and its aftermath created the first notable post-Independence ferment among the Hindus to gain political power and come out of the eclipse of the Gandhi-Nehru dynasty. Overseeing the demolition through benign inaction was the Prime Minister PV Narasimha Rao, an unassuming man of intelligence and a deep and enormous linguistic capacity from the Andhra country (notable was his facility in picking new human and computer languages). But PVNR’s main contribution was his reform of the Indian economy, which for the first time allowed Indians to experience the real middle class life. This boosted the growing confidence of Hindus and after a period of uncertainty culminated in the first NDA government under AB Vajapayee.

While as an adherent of the śruti I found his keeping of the hallowed title of Vajapayee without truly living up to it grating, he was a man of importance for the survival of the Hindu polity. His most important achievement was the conducting of the nuclear weapons tests totally surprising the mleccha and cīna enemies – this was a kind of boldness which had not been exhibited before. Next, he was able shepherd the nation through the economic blockade imposed by the evil mleccha-s and show that the economic platform, which PVNR had laid the foundations for, was indeed robust. In this period he had to handle the jihad of the marūnmatta-s in the Kargil war. The secularized Hindu army carried the day and showed that despite the mleccha attempts to curb them with sanctions they Hindus were not to be taken as walkovers. The mleccha-marūnmattābhisaṃdhi was at this point flummoxed by both the military victories and economic resilience of the Hindu nation and resorted to their usual trick of deploying the internal marūnmatta bomb – the legacy bequeathed on the Hindus by the faux Mahātman and Nehru. The most prominent among these attacks was the arson in Lāṭānarta, where emboldened marūnmatta-s burned down a train carrying Hindus killing many. The man who came to the fore in this dire situation was not ABV but his future successor the Lāṭeśvara from the tailakāra-jāti. It was due to him that the Hindus were able to show to the rākṣasa-like marūnmatta-s that they could not get away with their usual crimes. This was instrumental in bringing peace to the state and teaching a lesson to the marūnmatta in the only language he understands.

But then Hindus are renowned for dropping the axe on their own foot. Thus, lulled by the relatively good times the benign rule of ABV had brought, deciding not to take a long term vision, they instead facilitated the return of the Gandhi-Nehru dynasty via UPA-I. This government was led in proxy by the Helena of India who was a windfall for the mleccha-s, and she ably served as their agent in undermining the Hindu nation. To keep the Hindus in check, the marūnmatta-s were unleashed on a routine basis and this reached a culmination in the invasion of Mumbai on Nov 26 2008 by a mere band of 10 ghazi-s bringing back memories of Ikhtiyar al-Din Bakhtiyar Khalji, the hero of Bangladesh. As the UPA kept facilitating anti-heathen action, the NDA was unable to even put up a proper fight – ABV faded away into a vegetative state and his lieutenant, the aging saindhava LKA lost the plot in many ways (Note his egregious appointment of Kulkarni as an adviser). This only consolidated the grip of the Abrahamistic convergence against the Hindus. To worsen matters, it looked as though the cīna-s might launch a decisive strike on the enfeebled secularized Hindu army – things almost looked lost for the Hindu nation.

It was in such dire circumstances that the Lāṭeśvara became Dillīśvara in 2014. The mleccha-s having known his capacity from his restoring of the Lāṭānarta country greatly feared him. For 12 years they had kept him out their countries because they hated him as the symbol of what they hated most – the unconquered heathens of Hindustan who were the last great bulwark of that old and brilliant Indo-European heathenism, which they had either ground to dust or placed in museum closets. This heathenism was a rival worldview to all that the counter-religions of Abrahamism represented in their essence. Its very presence was a negation of the narratives of Abrahamism and it had to be exterminated. If there was one leader among the Indian masses who could give it a lifeline it was the Lāṭeśvara. Hence, they summoned all they could could in the form of their first responders to prevent his acquisition of power. They raised fake leaders like the broom-wielding koṭvāl of Delhi and the hazardous perpetuator of Gandhian blunders. But none of this worked in the long-run and the Lāṭeśvara took power.

Among the failures of the ABV-LKA duo was their inability to protect the homeland security of Bhārata from marūnmatta-s, śavasādhaka-s and other kaṇṭhaka-s. We had: the hijacking followed by the humiliating release of demonic ghazi-s; the train attack; the ghazwat on the Parliament. Further ABV was hobbled by the machinations of the possibly crypto-preta president KR Narayanan. This is where the Lāṭeśvara NM focused. Despite his inadequacies on the ideological front, his lieutenant Dobhal was able to be quite effective in curbing the violence of the marūnmatta-s. He also dented their ability to finance such operations by the secretive demonetization maneuver. His other lieutenant Rajnath Singh, again, despite his inadequacies, has done a reasonable job in prosecuting a vigorous assault against the secularized mutation of Abrahamism, namely the socialist terrorists of internal India. On the external front the he handled the confrontation with the belligerent Han by tackling the Doklam conflict really well. He also sent a message to the ghazi-s by directing the secularized Hindu army to launch “surgical strikes” against them. This had a psychological effect more than anything else – perhaps the Hindus were doing it for the first time since the Maratha punches delivered in their heydays.

On the economic front things are less clear, in part because I am not qualified to assess the matters too precisely. The general trends point to some success in this regard, especially in terms of curbing and to a degree reversing the damage caused by the UPA misrule. However, the demonetization and the goods and services tax, while done with good intentions and with long-term benefits in mind, might have affected many adversely; however, this is perhaps a matter of perception. On the external front, while NM’s foreign policy has been clearly more robust than that managed by the flaky Jaswant Singh under ABV, its success is not entirely clear. The handling of the Nuclear Suppliers Group matter does look like a failure to us. Finally, like a good Hindu king ought to do, NM has paid much attention to the issue of jana-kṣema and made major strides in this direction. He himself has led the svaccha-Bhārata-abhiyāna from front in attempt the impart the much-need civic sense to the undisciplined Hindus. The ground connectivity progress managed by Gadkari and railways by Prabhu/Goyal seem to be bright spots too. However, specific Hindu issues relating to temple administration, temple rights, animal husbandry and ground level prevention of the infection spread by dayi-s and evangelists have not been satisfactorily addressed.

That last point in the above discussion brings us to proverbial “elephant in the room”. During the UPA rule the mleccha-marūnmattābhisaṃdhi had systematically infiltrated the judiciary and the civil service with pro-Abrahamistic elements. As India is ruled by a democratic form of government, NM and his lieutenants are having a difficult time undoing the evil of this infiltration. This in part is the basis of their inability to do much for certain specific Hindu issues. Going forward, this could result in enormous damage to the Hindus. One only hopes that NM is doing his best to uproot these plants of the enemies completely revamp the affiliation of the administrative machinery. Beyond this, our enemies are certainly rattled by this Julian-like come back of the H under NM. But will he prove to be just that – a Julian?

The mleccha-s and the marūnmatta-s would definitely want it to end that way and NM is going to have to fight hard to keep the saffron flag fluttering. Among other things they would continue their strategy of raising false leaders, like the man of the broom, in various local settings to create a general ferment. The idea here is not to create a rival for NM but to damage the impact of his janakṣema. The śava-s would be used to harry the polity – e.g. the Sterlite Copper agitation in the Tamil country. They would also be tempted to deploy the sword arm of the marūnmatta to attempt something big and bloody. Their new agent in TSP Imran Khan might also be deployed for exerting pressure from western Mohammedan fragment of India. The agent of the Eastern Mohammedan fragment, the white-shrouded evil daughter of Bakhtiyar would be used to expand violence against the Hindus in the east. A political alliance would created around the Kangress and the dredges of the old UPA to attack the NDA like the various enemies of Sudāsa ganging against him. The cīna-s might try to fish in these troubled waters too but we suspect that Trump’s trade-war might come to the aid of the Hindus here. The mleccha deep-state itself is having problems due to the unexpected triumph of Trump. This might keep them busy and Hindus should exploit that. However, the techniques developed against Trump are and will be deployed against NM and the Hindus in India. Finally, the mleccha-s know that if they incite something big and bloody too early or too late it could end up consolidating the Hindus. Hence, we tend to think that the path they would prefer is that of a “million mutinies”. The malcontents from the depressed classes and other groups will be cultivated and deployed. The purchased “news traders”, much like the Piṇḍāri purchase by the English, would be used to amplify these disturbances. Reinforcements would be sent to the socialist terrorists. The idea would be to simultaneously take the sheen of the vikās and break up the unity among the Hindus. If NM returns to power then the stage would be set for bigger and more gory confrontations whose exact unfolding would depend on other geopolitical events of the future.

As a tailpiece we should mention that within hours of completing the body of this text the news reached us that one of the protagonists of the above story, ABV, has passed away after a long life — the last of those were hardly worth living. We have been critical of him on these pages on more than one occasion but now that he belongs the realm of the manes we have to acknowledge his historic role with gratitude. He certainly built the platform that Hindus can use to move forward and the one that the Lāṭeśvara is using. His end brings down the curtain on this turn in the meandering of the Hindu nation. Many Hindus have been spending the last four years doing nothing but bitching about NM. They are nothing but armchair activists who have not participated in electoral contests or organized protective services on the ground. One thing we can tell such folks is do your own little bit for the dharma at the grassroots level. Do not expect the prime minister or mahānta yogī Ādityanātha to be a quantum entity who is at multiple places at the same time performing bābāistic miracles. Also remember that certain parts of the country are seriously compromised with the infections and batting for them would not save them unless they are willing to chip in too. Finally, this period has also seen the death of the Dravidianist leader, the hater of brahma, and the corpulent woman who attempted to destroy the Kumbhaghoṇa maṭha. The Hindu leadership needs to act quickly in this window of opportunity to eradicate the evil of Dravidianism.

Posted in Politics | Tagged , , , ,

The geometric principles behind discrete dynamical systems based on the generalized Witch of Agnesi

Consider the family of curves defined by the equation following parametric equation

x=\dfrac{1}{\sqrt{\pi\left(1-a\right)}}\left(\cos\left(\alpha\right)\left(t+1\right)+\dfrac{\sin\left(\alpha\right)\left(1+at+at^2+at^3\right)}{1+t^2}-1\right),

y=\dfrac{1}{\sqrt{\pi\left(1-a\right)}}\left(-\sin\left(\alpha\right)\left(t+1\right)+\dfrac{\cos\left(\alpha\right)\left(1+at+at^2+at^3\right)}{1+t^2}\right)

where \alpha= \textrm{atan}(a) and -1\le a \le 1

It defines a family of probability distribution functions (PDFs): This can be seen from the above equations because

\displaystyle \int_{-\infty}^\infty y\dfrac{dx}{dt} dt=1

Figure1_Miroid_PDFsFigure 1

Examples of these PDFs are illustrated in Figure 1. One can see that when a=0 it is symmetric and reduces to a Cauchy distribution, which was discovered by Poisson and Cauchy. This distribution is famous for having “fat tails” and violating the Central Limit Theorem. A simple geometric example of this distribution is the following: Let the point P=(0, 1) be the source of rays that are emanated at an equal angular separation from the adjacent ray. Then the density of the x-intercepts of the rays is equivalent to the PDF corresponding to a=0. The family of PDFs in Figure 1 are a generalization of the Cauchy distribution case. When -1 \le a < 0 the distribution is more peaked and skewed to the left. Conversely, when 0< a < 1 the distribution is less-peaked and skewed to the right. When a\to 1, the distribution become more and more flat and uniform. They all have fat tails like the Cauchy distribution case. Are these other distributions encountered anywhere? While we have some suspicions that such distributions might occur in the path-lengths of searching behaviors of certain organisms, this is a question we have not been able to definitively answer. Nevertheless, the function behind the above PDFs generates a very interesting class of maps exhibiting chaotic behavior and this is what we shall discuss below.

The function which determines the shapes above PDFs can be written as,

y=\dfrac{1+ax+ax^2+ax^3}{1+x^2}

Figure2_Miroid_fx

Figure 2

Examples of this curve as illustrated in Figure 2. One notices that it essentially produces unscaled versions of the above PDF curves, which are rotated about the point (-1,0) by the angle \alpha= \textrm{atan}(a). As a result, the x-axis of the PDF curves now becomes the asymptote of these curves which has the equation y=ax+a. When a=0, again this curve reduces to the shape-determining curve of the Cauchy distribution, i.e. the Witch (of Agnesi). For a=1 it becomes identical with the 45^o asymptotic line.

We then consider the following mapping procedure:

1) Take (equally-spaced) points on a circle with center at origin and radius r. For reasonable aesthetics we commonly take r=5

2) Then subject each of these points P_0=(x_0, y_0) to the iterative mapping:

x_{n+1}=by_n+f(x_n)

y_{n+1}=-x_n+f(x_{n+1})

Here, b is a constant that is taken as 1 or a value close to it; .99 \le b \le 1.001 produces the best aesthetics.

f(x)=\dfrac{1+ax+ax^2+ax^3}{1+x^2}, i.e the above shape-determining function of the above PDFs.

3) Plot the orbits of all P_0=(x_0, y_0) on the circle under this map.

Figure3_Miroid_mappingFigure 3

This mapping procedure is illustrated with an example in Figure 3. We start with a circle shown in red, r=5, on which 360 equally spaced starting points P_0 lie. We then use P_0 to sample the curve f(x) with a=0.525 twice, as indicated in the above map, to get the next point. The curve f(x) is shown in green. Its unrotated equivalent, which determines the shape of the corresponding PDF is shown in blue. For this map we take b=1 and the iterate it for 250 times. The 250 points comprising the orbit of one P_0 are then plotted. This is repeated for all the 360 P_0s to get the map show in black in Figure 3. Superimposed on the map is the orbital path of a particular P_0 (shown in cyan) for the 250 iterates. The evolution of the orbit is indicated by orange triangles whose three vertices are respectively the two points sampled on f(x) (shown in red and green on the curve) for a given mapping step and the third is the corresponding point on the map. One can see that the map initiated with this particular P_0 samples only 4 specific regions of the f(x). Consequently, the orbit results in the six closed loops. Other P_0 might sample f(x) more extensively and uniformly, resulting in a more widely dispersed or chaotic orbit. Thus, the union of the orbits of all the initiating P_0s on our circle results in a map with fractal structure (Figure 3). The chaotic nature of map becomes immediately apparent from the high degree of sensitivity of the orbits to the starting points.

Having worked out this map, we realized that orbits of single points under above mapping with appropriate change of coordinates are related to the map published in 1980 by Gumowski and Mira (G-M). This was among the first strange attractors for which we, like many others before and after us, had written code for (though we must mention that to date we have not read Gumowski and Mira’s paper). It was then than we became curious about the rotational periodicity exhibited by some examples of the G-M map resulting in rotational quasi-symmetry. We were able to finally provide the rationale for this geometry when we discovered the map which we are currently discussing. The maps discussed here show a strong tendency for rotational periodicity — for example, the above example shows a 6-fold periodicity — what we term the n-ad structure. Indeed, these maps are better for understanding the rotational periodicity than the original G-M maps because all the powers of x in f(x) have the same sign in this map.

In order understand the rotational periodicity in the map we shall have to consider two cases of it separately: first, the case when the radius of the circle on which the starting P_0s lie is large; this is empirically taken as r \ge 4. The second case is when it is small; this is take r< 4. To examine the former case let us consider the cases in the following figures.

Figure4_Miroid_rad5_b9985Figure 4. Here b=0.9985, r=5 and a is the sequence of the first few irreducible vulgar fractions, both positive and negative, i.e. the first few fractions of the form \tfrac{p}{q}, where p and q are mutually prime. Each P_0’s orbit is plotted in 1 of 7 different shades of blue in this figure and all subsequent ones. Thus, we keep cycling through these 7 shades for after every 7th P_0.

Figure5_Miroid_rad5_b9985Figure 5. Here b=0.9985, r=5 and a is the sequence of further positive irreducible vulgar fractions.

Figure6_Miroid_rad5_b9985Figure 6. Here b=0.9985, r=5 and a is the sequence of further irreducible vulgar fractions which are negatives of the above.

Few features become immediately apparent:

1) The maps exhibit strong rotational periodicity. E.g. for a=0 we get a tetrad structure.

2) At certain values there is considerable rotational symmetry e.g. a=\tfrac{1}{6}, a=-\tfrac{3}{4}, -\tfrac{1}{7}.

3) The extreme cases of this are when the map collapses to a completely symmetric radial structure for a=\tfrac{1}{2}, -\tfrac {1}{2}, -1

4) As the value of a \to \pm 1 the aspect ratio of the map becomes lower and lower along the y-axis and converges to a straight line-segment at the limiting values of a.

5) For values of a close to 0 on either side we get maps with aspect ratio closer to 1.

These observations allowed us to develop a formal description of the geometric principles behind these maps:

1) Since -1\le a \le 1 it can be considered the cosine of an angle \gamma. Thus, we can write:

\textrm{acos}(a)=\gamma=\dfrac{2\pi}{n/m}, where n,m are mutually prime integers.

This fraction \tfrac{n}{m} is the shape-determining fraction of the map (Figure 7). When the radius of our starting circle r \ge 4, then the basic rotational periodicity of the map is determined by n and it shows an n-ad structure(Figure 7). Thus, when \tfrac{n}{m}=3, \gamma=\tfrac{2\pi}{3}. Hence, a=\cos\left(\tfrac{2\pi}{3}\right)=-\tfrac{1}{2}. Thus, as we see in Figure 4, a=-\tfrac{1}{2} has a triad structure corresponding to n=3. Similarly, when \tfrac{n}{m}=4, a=\cos\left(\tfrac{2\pi}{4}\right)=0; thus, a=0 results in a map with tetrad structure corresponding to n=4 (Figure 4).

2) If \gamma=\textrm{acos}(a), then this angle \gamma can be taken to be the interior angle of a polygon inscribed in a circle (Figure 7). Now, flatten this circle into an ellipse such that the eccentricity of the ellipse is |\tan(\alpha)|=|a| (Figure 7). Thus, 0\le |a| \le 1 describes ellipses within which the map is bounded, which span the entire range from one close to a circle when |a| \to 0 to one close to a segment when |a| \to 1. The polygon inscribed in the original circle correspondingly gets flattened into a polygon inscribed in the ellipse (Figure 7). This polygon describes both the n-ad structure of the map as described above, whereas the eccentricity of its bounding ellipse describes the aspect ratio of the maps under consideration.

Figure7_Miroid_geometryFigure 7. The original generalization of the Witch is in red. The free-rotating version used in the current maps is in green. The polygon inscribed in the circle defined by the \angle{\gamma} is shown in blue dotted segments. The ellipse whose eccentricity is determined by the |a|=|\tan(\alpha)| is shown in red, with the final polygon inscribed in it in violet.

3) In order to illustrate the above principles and describe the finer intricacies of the structure of the map beyond the “coarse features” accounted for by the above rules we need to examine several specific examples. Since cases like a=\pm \tfrac{1}{2} result a “collapse” of the map to a radial structure (Figure 4), to explain in its entirety the role of the fraction \tfrac{n}{m} in determining map shape we add a small positive \epsilon to define a=\cos\left(\tfrac{2\pi}{n/m}\right)+\epsilon.

Figure8_Miroid_rad5_b9985_d0025Figure 8. In this set of maps the radius of the starting circle r=5, b=0.9985, \epsilon=.0025. a is expressed as sequence of cosines shown with the corresponding angles and \tfrac{n}{m} above each map in this and the subsequent figures.

In the first 7 cases, \tfrac{n}{m}=3,4,5,6,7,8,9. According to the above described geometric rules we find that the map adopts a triad, tetrad, pentad…nonad structure with decreasing aspect ratio (Figure 8).

When \tfrac{n}{m}=\tfrac{9}{2},\tfrac{11}{2},\tfrac{13}{3},\tfrac{15}{4},\tfrac{17}{4}, we see an obvious 9-, 11-, 13-, 15-, 17-ad structure but with much higher aspect ratios than what would be expected if the denominator were 1. This is because the a=\cos\left(\tfrac{2\pi}{n/m}\right)+\epsilon results in eccentricities closer to 0. Thus, choosing such \tfrac{n}{m} allows you to obtain n-ad structures at higher aspect ratios (Figure 8).

Further, note the internal structure of the map, i.e. the region close to the center, setting aside the above described patterns for the more peripheral structure described above. The following \tfrac{n}{m} are notable:

For \tfrac{9}{2} we get a tetrad interior;

For \tfrac{11}{2} — pentad interior;

For \tfrac{13}{3} — tetrad interior;

For \tfrac{15}{4} — triad interior;

For \tfrac{17}{4} — tetrad interior (Figure 8).

This indicates that for maps with high aspect ratio, the n-ad structure close to the center is determined by the number k_1=\left \lfloor \tfrac{n}{m} \right \rfloor. In some cases, the value of k_1 can dominate the shape of the map. For example, when k_1=\left \lfloor \tfrac{17}{5} \right \rfloor=3, \left \lfloor \tfrac{19}{3} \right \rfloor=6 we see that k_1 is the dominant n-ad of the shape. However, keeping the primary n-ad rule in each of these cases, the periphery shows 17 and 19 spikes respectively.

Next, note the structure of the map where \tfrac{n}{m} =\tfrac{17}{3}. At the periphery we see 17 “spikes” keeping with the basic structure determining number n=17. Close to the center, we see the pentad structure keeping with the principle described above: \left \lfloor \tfrac{17}{3} \right \rfloor=5 However, the overall map is dominated by a hexad structure — i.e., the 17 spikes are arranged into a hexad pattern. This hexad pattern is also seen in the structure of middle layer of the map. This gives us another principle: Especially for larger n if k_2=\textrm{round}\left(\tfrac{n}{m} \right) > \left \lfloor \tfrac{n}{m} \right \rfloor, then we can get a further layer of structure with a n-ad structure determined by k_2. This can again be seen in the case of \tfrac{19}{4}, where k_2=5. This results in a pentad dominance with a middle pentad layer between the outer 19 spikes and inner tetrad structure (Figure 8).

4) Finally, we consider the case when the starting circle has r<4. In this range we observe that the maps do not entirely obey the above rules. We see a progressive “step-down” in the n-ad structure for values other than \tfrac{n}{m}=3. This is illustrated with examples in Figure 9.

Figure9_Miroid_radphi_b9985_d001Figure 9. Here r=\tfrac{1}{\phi}, where \phi is the Golden ratio; b=0.9985; \epsilon=.001.

We observe right away that for \tfrac{n}{m}=4 the structure is only incipiently tetrad. For \tfrac{n}{m}=5, 6, 7, 8, on the other hand the n-ad structure of the map is respectively a tetrad, pentad, hexad and heptad. Thus, the rotational periodicity rather being equal to n comes down to n-1. For the other fractional \tfrac{n}{m} we see only the k_1 structure, where k_1=\left \lfloor \tfrac{n}{m} \right \rfloor. We do not see the structure derived from n in \tfrac{n}{m}. In the range \tfrac{1}{\phi} \le r \le 4 we see a gradual recovery of the structure that clearly manifests at r\ge 4. We illustrate this in Figure 10.

Figure10_Miroid_rad2_b9985_d001Figure 10. Here r=2; b=0.9985; \epsilon=.001.

We observe that for \tfrac{n}{m}=4, 5, 6, 7, 8, 9, \tfrac{9}{2} the typical n-ad structure determined by n as seen in the maps where r\ge 4 is restored. However, for the remaining \tfrac{n}{m}, k_1=\left \lfloor \tfrac{n}{m} \right \rfloor is the dominant determinant of the map’s rotational periodicity (Figure 10) and we have to wait till r \ge 4 for a n-ad structure determined by n to emerge. The emergence of the clear n-ad structure only at higher radius values combined with a more complex chaotic behavior at lower radius values is also seen in the well-known Zaslavsky map based on the Hamiltonian of a kicked rotor. However, it is notable that maps with these values of \tfrac{n}{m} at low r values have some complex internal structures that are difficult to account for by any of these rules. For example, consider \tfrac{n}{m}=\tfrac{13}{3} (Figure 10). In each of the 4 outer projections of the tetrad structure we see an internal hexad attractor. Inside that hexad attractor we see a further pentad attractor. Within the central tetrad element of this map we see a triad excluded space. Finally, in the border of this central tetrad element we see a 7-fold attractor! This is reminiscent of the structures seen in the famous Standard map of Chirikov.

In conclusion, as we saw with an earlier map that we had discovered and the maps derived from certain Hamiltonians of kicked rotors/oscillators, there is a hidden role for the irreducible vulgar fractions in determining the shape of the map. While it is easy to see that the rational numbers are distributed uniformly, that is not the case if they are ordered as per their rank based on their numerators and/or denominators. Examples of such fraction sequences are those described by Moritz Stern, Farey and Brocot. Even as in the fractal structure defined by these fraction sequences, the rank of the fraction is central to the definition of the map’s rotational periodicity in current case. The higher ranked \tfrac{n}{m}, i.e. the low magnitude integers like 3, 4, 5, 6 dominate the n-ad shape of the map relative the other rational numbers in their interstices. However, those interstitial values interact with these dominant values to give layers of complex structure to the map.

Posted in Scientific ramblings | Tagged , , , , , , , , , ,

Reflections on our journey through the aliquot sums and sequences

The numerology of aliquot sums and perfect numbers
The numerology of the Pythagorean sages among the old yavana-s is one of the foundations of science and mathematics as we know it. One remarkable class of numbers which they discovered were the perfect numbers — teleios as they termed it. What are these numbers? Let n be a number and d_j be all its proper divisors, i.e. those divisors of n, which are less than n. Then we can define an arithmetic function known as the aliquot sum s(n) thus,

\displaystyle s(n)=\sum_{j=1}^k d_j; d_k<n

For example, let us consider the number 10. Its divisors are 1, 2,5,10. Its proper divisors are 1, 2, 5. Hence, s(10)=1+2+5=8. Now, if s(n)=n then n is called a perfect number (termed pūrṇāṅka in Jagannātha’s Sanskrit edition of Euclid). From Figure 1, we can see that the numbers 6 and 28 are perfect numbers. The Pythagorean interest in them also becomes apparent from the fact that these numbers are associated with certain natural periodicities that have an old Indo-European significance. This becomes clear from their occurrence even in old Hindu tradition. The number 6 is associated with the 6 seasons in brāhmaṇa-s like the Śatapatha-brāhmaṇa and encoded into the śrauta altar. Similarly 28 is also encoded into the altar according to the Śatapatha-brāhmaṇa and corresponds to the count of the nakṣatra-s or days of the lunar month. The number 28 is also used in Vaidika tradition as one of the prescribed counts for the japa of the Savitṛ gāyatrī

aliquot_Perfect_numbers_Figure1Figure 1

Returning to the arithmetic, with our above example of s(10), we can see that s(n)n. Such numbers are called abundant numbers. Now, a subset of the proper divisors of 20 add up to 20 (Figure 1). Hence, it is also a semi-perfect or a pseudo-perfect number. There is a rare set of abundant numbers for which no subset of their proper divisors add up to them; they are known as weird numbers. For example, s(70)=74; hence, it is an abundant number. However, no subset of its proper divisors, 1, 2, 5, 7, 10, 14, 35 add up to 70. Hence, 70 is a weird number. The next weird number is 836. Thus, due their rarity majority of abundant numbers are semiperfect numbers.

One of the high points of yavana brilliance was the discovery of a general formula for perfect numbers. In Book 9, proposition 36 Euclid states:

“ean apo monados hoposoioun arithmoi hexēs ektethōsin en tē diplasioni analogia, heōs hou ho sumpas suntetheis prōtos genētai, kai ho sumpas epi ton eskhaton pollaplasiastheis poiē tina, ho genomenos teleios estai.”

If as many numbers as we please beginning from an unit be set out continuously in double proportion, until the sum of all becomes prime, and if the sum multiplied into the last make some number, the product will be perfect.

In modern terms we can lay it out thus: If the sum of the series of the powers of 2, where the power are integers \ge 0, is a prime number then the product of that prime with the last power of 2 in the series is a perfect number:

q=\displaystyle \sum_{j=0}^n 2^j

If q is a prime then q\cdot 2^n is a perfect number. Let us take the first few examples.
2^0+2^1=3\Rightarrow 2^1\times 3=6
2^0+2^1+2^2=7\Rightarrow 2^2\times 7=28
2^0+2^1+2^2+2^3=15 \Rightarrow Not a prime
2^0+2^1+2^2+2^3+2^4=31\Rightarrow 2^4\times 31=496
2^0+2^1+2^2+2^3+2^4+2^5=63\Rightarrow Not a prime
2^0+2^1+2^2+2^3+2^4+2^5+2^6=127\Rightarrow 2^6\times 127=8128
After this point the perfect numbers become much less frequent and large.
2^0...2^{12}=8191 \Rightarrow 33550336
2^0...2^{16}=131071 \Rightarrow 8589869056
2^0...2^{18}=524287 \Rightarrow 137438691328

Another way of expressing this is thus: Given a prime number p if M_p=2^p-1 is also a prime then P=2^{p-1}\cdot(2^p-1) is a perfect number. The corresponding prime numbers M_p are today famous as the Mersenne primes. For all p <100, the following p yield M_p: 2, 3, 5, 7, 13, 17, 19, 31, 61, 89
The corresponding M_p are:
3
7
31
127
8191
131071
524287
2147483647
2305843009213693951
618970019642690137449562111

The corresponding perfect numbers are:
6
28
496
8128
33550336
8589869056
137438691328
2305843008139952128
2658455991569831744654692615953842176
191561942608236107294793378084303638130997321548169216

These primes M_p start getting huge and rare rapidly. We computed the above in a few seconds with a modern programming language and computer. However, some of them mark historic feats of arithmetic computation by the unaided human brain in the pre-computer era. For instance, Leonhard Euler computed the 8th M_p (10 digits) and the corresponding perfect number. The Russian village mathematician I.M. Pervushin went further by computing the 9th of these numbers ( M_p= 19 digits). With the Great Internet Mersenne Prime Search we now have 50 of them and the corresponding perfect numbers. This also helps us to see why the M_p always end in 1 or 7 and the corresponding perfect numbers end in 6 or 28. That the above are the only even perfect numbers was established by Euler. Unlikely as they seem, there has been no formal proof to show that no odd perfect numbers exist. The modern efforts also show that the perfect numbers are rarer than what the yavana sages thought them to be. The old Pythagorean numerologist Nicomachus states:

“It comes about that even as fair and excellent things are few and easily numerated, while ugly and vile ones are widespread, so also the abundant and deficient numbers are found in great multitude and irregularly placed – for the method of their discovery is irregular – but the perfect numbers are easily enumerated and arranged with suitable order; for only one is found among the units, 6, only one among the tens, 28, and a third in the rank of the hundreds, 496 alone, and a fourth within the limits of the thousands, that is, below ten thousand, 8128.”

The above statement suggests that Nicomachus might have thought that for each decade there is one perfect number. Alternatively, he might have simply stopped counting with the greatest perfect number he knew. That it was the former is strengthened by Platonic siddha (to use Gregory Shaw’s term), Iamblichus, even more explicitly claiming that there is one perfect number per decade. That, however, is clearly wrong as the next perfect number 33550336 is in the crores. In any case the modern confirmation of the real rarity of perfect numbers vindicates the philosophical analogy drawn from these numbers by the yavana siddha — the scarcity of truly perfect things as opposed to the profusion of the supernumerary and the deficient. With respect to the easy enumeration of the perfect numbers Nicomachus and Iamblichus likely meant Euclid’s proposition. This rarity of perfect numbers indicates that the sum of the reciprocals should converge to a constant:

\displaystyle C_P=\sum_{j=1}^n \dfrac{1}{P_j}= \dfrac{1}{6}+\dfrac{1}{28}+\dfrac{1}{496}+\dfrac{1}{8128}... \approx 0.20452014283893...

It would be immensely remarkable if this constant turns up somewhere in nature.

Abundant numbers
In any case, this C_P provides a bound for the distribution of abundant numbers and thus, brings us to the point of whether Nicomachus’ statement regarding the abundant numbers is really so? This was what we set out to investigate in our youth armed with a rather meager arithmetic knowledge and a computer. Computing the first few abundant numbers yields a sequence like below:
12, 18, 20, 24, 30, 36, 40, 42, 48, 54, 56, 60, 66, 70, 72, 78, 80, 84, 88, 90, 96, 100, 102, 104, 108, 112, 114, 120, 126, 132, 138, 140, 144, 150, 156, 160, 162, 168, 174, 176, 180, 186, 192, 196, 198, 200, 204, 208, 210, 216…

A few rules become immediately apparent:
1) if P_j is a perfect number then k\cdot P_j is an abundant number for all k \ge 2. Thus, P_1=6 initiates a line of abundant numbers 12, 18, 24, 30…. P_2=28 initiates 56, 84, 112…

2) We notice that beyond these a few abundant numbers emerge in the interstices e.g. 20, 88 etc. A notable class of these emergent abundant numbers are of the form 2^k\cdot p_j, where p_j is the j^{th} odd prime and k \ge 2. The first few of these are tabulated below.

aliquot_table1

These are all shown as red points in panel 1 of Figure 2. One notices that for each jump of k we get a jump in these abundant numbers. Of these, some like 12, 56 and 992 are already accounted for as doubles of the perfect numbers 6, 28 and 496 but the rest are distinct. Their multiples, as with the perfect numbers, are also further abundant numbers.

3) A few further abundant numbers emerge in the interstices, which have a more complex description. They found new lineages of abundant numbers as their multiples continue to be abundant numbers. The first of these is 70=2\times 5 \times 7. 70 is the product of successive odd primes 5, 7 with 2 leaving out 3, which would yield already accounted-for abundant numbers in a product with 2 via the perfect number 6. Another such is 2002=2\times 7 \times 11 \times 13. Here 5 is left out because that will again result in already accounted-for abundants in a product with 7. Likewise, leaving out 7, we have 1430=2\times 5\times 11\times 13. For further numbers in this category we need the next power of 2, e.g. 9724=2^2 \times 11\times 13\times 17.

4) Till n=1000 odd abundant numbers are very rare. The A[232]=945 is the first odd abundant number and till n=200000 there are only 391 odd abundant numbers as opposed to 49090 even abundant numbers. Of these first 391 odd ones, 387 are divisible by 15. The remaining 4 which are not namely 81081, 153153, 171171, 189189 are divisible by 9009. All odd abundant numbers necessarily need to have the product of at least 3 distinct odd primes as a divisors. As with other abundant numbers, the multiples of odd abundant numbers are also abundant numbers. Based on the separation between the odd abundant numbers, we observed that the first of them 945 is the first of a lineage of odd abundant numbers, which are generated by the formula: A_o=3 \times (315+210k), where k=0,1,2...51. Similarly, we observed that a related formula A_o=11 \times (315+210k), where k=0,1,2...192 produces a continuous run of 193 odd abundant numbers starting from 3465. After k=51 and k=192 respectively these formulae do not necessarily produce abundant numbers; nevertheless numbers emerging from these rules continue to remain enriched in odd abundant numbers. Of course, the other emergent odd abundant numbers might have further less-apparent rules. In any case, it appears the difference between two successive odd abundant numbers is most of the times divisible by 2 \times 3 \times 5 =30 and always divisible by the perfect number 6.

Thus, unlike what the yavana siddha-s thought, the abundant numbers are not entirely unruly. They have complex patterns, but can be described by some rules. The biggest bulk of them are children of perfect numbers — like mortal descendants of the immortal gods. This leads us to the growth of the sequence of abundant numbers, which exhibits striking regularity (Figure 2).

aliquot_abundance_figure2Figure 2.

Given that the sum of the reciprocals of the perfect numbers converges to a constant C_P and given what we have seen above regarding the abundant numbers, they should grow at the upper bound by the equation y=\tfrac{x}{C_P} \approx 4.89x (the dark red line panel 1 of Figure 2). However, since the progeny of perfect numbers are not the only abundant numbers and several emerge by the other rules mentioned above A[n] should grow at a lower rate. During our initial foray into abundant numbers, by empirical examination we thought this growth rate might be exactly 4 (Figure 2, panel 1, light blue line). However, with better computers and computation of 49481 abundant numbers, we later realized that the rate was actually slightly more than 4 (Figure 2, panel 1, dark green line). Another way of visualizing the same is by defining the density of these numbers as the ratio of the number of abundant numbers \le to a certain number n to n,

D= \dfrac{\#A\le n}{n}

This is shown in Figure 2, panel 2, where we see D converging to a value between 0.248 and 0.247 (red and blue lines). This has been a topic of deep investigation in modern mathematics, starting with the likes of Sarvadaman Chowla and Paul Erdős, and indeed the above has proven to be the approximate bound of the density of abundant numbers. We were quite pleased to have semi-empirically arrived at it for ourselves. Thus, even as the odd and even numbers are distributed in a 1:1 ratio, after initial jitters the ratio of deficient to abundant numbers converges to a constant of \approx 4.04 with new lineages of abundant numbers constantly emerging in the interstices of the established ones to maintain a linear growth at this rate.

The basic features of the aliquot sequences
The process of obtaining aliquot sums of a number n can be applied iteratively (the aliquot map): s(n)=n_1 \rightarrow s(n_1)=n_2 \rightarrow s(n_2)=n_3.... The sequence ali(n)=n, n_1, n_2, n_3... is called the aliquot sequence of n. Thus, if we start with n= 20 we get the sequence: 20, 22, 14, 10, 8, 7, 1, 0. More generally, by computing aliquot sequences for all numbers from 1:1000, we observe the following:
1) The number 1 converges in two steps to 0.
2) All primes converge in 3 steps, p, 1, 0.
3) Perfect numbers converge in 1 step to themselves.
4) Certain numbers converge to a perfect number. E.g. 25, 95, 119, 143, 417, 445, 565, 675, 685, 783, 909, 913… converge to 6; 608, 650, 652, 790 converge 496. We observe that these numbers have given the appellation “aspiring numbers”.

5) Notably, 220 converges to 284 and 284 converges to 220. ali(562)=562, 284, 220. Thus, if from whatever starting point if one reaches 284 or 220 one cycles between them. Such a pair is termed a pair of amicable numbers and was probably known to Platonists as indicated by the heathen Sabian from Harran, Thabit ibn Kurra’s knowledge of these numbers. Thabit discovered a rule to produce a lineage of these numbers, likely drawing on the rule to generate even perfect numbers: Let a=3\cdot 2^{n-1}-1, b=3\cdot 2^n-1, c=9\cdot 2^{2n-1}-1 and n\ge 2. If a,b,c are primes then we can compose the amicable pair as a_1=2^n \cdot ab, a_2= 2^n \cdot c. For n=2 we get the pair 220, 284; n=4 produces 17296, 18416; n=7 produces the pair 9363584, 9437056. However, there are many more amicable numbers between these pairs which cannot be captured by this rule. For example, one can computationally show that 1184, 1210 are an amicable pair. Long after the days of Thabit, starting from Euler down to our times further rules have been found to capture more amicable pairs.

6) If perfect numbers are auto-cycles under the aliquot map, the amicable numbers can be considered 2-cycles. While we do not know if all higher cycles exist under the aliquot map, we can computationally find some of them. For example the pentad 12496, 14288, 15472, 14536, 14264 constitute a 5-cycle. Any number in this pentad will cycle through these values. Even more remarkable is this sequence 14316, 19116, 31704, 47616, 83328, 177792, 295488, 629072, 589786, 294896, 358336, 418904, 366556, 274924, 275444, 243760, 376736, 381028, 285778, 152990, 122410, 97946, 48976, 45946, 22976, 22744, 19916, 17716. These constitute a 28-cycle and any number in this 28-ad will cycle between these values. The lowest member of a 2- and greater cycle is always an abundant number.

7) Still other numbers will eventually converge to an odd prime and via that prime reach 0. There is a remarkable pattern in terms of the preference of the prime via which convergence occurs (Figure 3). 43 is the most preferred prime for convergence for n=1:1000 (any links to Heegner numbers or twin primes?). We are not clear as to whether this trend survives with increasing n.

Aliquot_convergence_P_figure3Figure 3

8) If we leave out the starting n will every other integer be reached by rest of the aliquot trajectory of some n? We can easily provide the answer to this question as no. For example, 2=1+1. You cannot have two 1s as proper divisors, hence 2 can never be reached from any other number under the aliquot map. Similarly, 5=4+1=2+3. But each of these sums leading to 5 cannot be a s(n) because we would leave out divisors 2 and 1. Thus, 5 can never be reached from any other number under the aliquot map. On the other hand, a number n=p+1 (where p is a prime number) is never untouchable because s(p^2)=p+1. Similarly, a number n=p_o+3 (where p_o is an odd prime) is never untouchable because s(2p_o)=p_o+3. Nevertheless, some numbers are not reached easily until one of the above configurations is encountered for the first time. For example, ali(1369=37^2)= 1369, 38, 22, 14, 10, 8, 7, 1, 0 contains 38=37+1 for the first time. Similarly, ali(2209=47^2)=2209, 48, 76, 64, 63, 41, 1, 0 contains 48=47+1 for the first time. But the number 52 lies a in sweet spot as as neither 51=52-1 nor 49=52-3 are primes and is untouchable from any other number under the aliquot map. These are some obvious examples of untouchability and touchability; Erdős has shown that ultimately there are an \infty of cases.

Patterns in the convergence length of aliquot sequences
Are these the only convergence patterns seen in the aliquot sequences? Is there any further pattern to the number of iterations needed to converge? To address these questions we can define a further sequence f[n] where each element is the number of iterations taken by the integer n to converge. The plot of f[n] for the first 1000 elements is shown in Figure 4.

aliquot_convergence_l_figure4Figure 4

The picture is quite remarkable — the majority of values are rather pedestrian but from time to time there are huge eruptive values. The perfect numbers ( f[n]=1), 1 and the primitive aspiring numbers, e.g. 25 ( f[n]=2), and primes ( f[n]=3) form the lowest values of f. f[n]=3 might also be reached by certain secondary aspiring numbers like 95 or 119. Of these the primes are the most common. It is quite obvious that even numbers have significantly longer convergence paths than odd numbers ( p=10^{-10}; Figure 5). We also observed that on an average the abundant numbers have significantly longer convergence paths than the remaining numbers ( p=5.3 \times 10^{-9} for n=1:1000). This holds even after the primes are removed from the non-abundant numbers ( p= 1.9 \times 10^{-8} for n=1:1000). Similarly, if we compare even abundant numbers and even non-abundant numbers, which occur in the roughly similar counts, the abundant even numbers still have significantly longer trajectories the non-abundant even numbers under the aliquot map ( p=3.2 \times 10^{-7}). Due to the relative rarity of odd abundant numbers, these effects are likely to persist beyond n=1000. The basic statistics for the convergence trajectory lengths for different types of numbers from n=1:1000 are tabulated below and summed up in Figure 5.

\begin{tabular}{|l|r|r|r|} \hline Number & Median & Mean & Max \\ \hline Even & 12 & 21.7 & 749 \\ \hline Odd & 4 & 4.9 & 17 \\ \hline Abundant & 15 & 34.04 & 749 \\ \hline Non-abundant & 5 & 6.76 & 25 \\ hline Non-abundant Non-p & 7 & 7.84 & 25 \\ \hline Even-abundant & 15 & 34.16 & 749 \\ \hline Even-non-abundant & 10 & 10.36 & 25 \\ \hline \end{tabular}

Aliquot_abundant_l_box_Figure5Figure 5

During our initial foray into the first 200 terms of this sequence it appeared that certain integers, like 138, never converged under the aliquot map. Going on till n=1000 more such terms appeared; however, better computation showed us that the aliquot sequences for some of these n indeed converge after a large number of steps after growing to monstrous values. It was then that we learned that the mathematicians have been studying this problem quite a bit computationally starting with Derrick Lehmer-II (the son of the father-son pair of arithmeticians), one of the doyens of computational mathematics. He was the first who, back in his days after what was a tough fight, showed that ali(138) indeed converges. For us, the hardest nut to crack for n=1:1000 was f[840]. It simply would not complete in our laptop at home even after running it for over a day with an efficient divisor finding function. Nor did it complete on our primary work station used for most of routine computations. Then we had to bring out our Indrāstra, a 120 core machine that we use for big things. For that we had to first write a multi-threaded version, which was run on 100 cores of this machine and it completed f[840] overnight. We term these large f[n] as the monster numbers. For n=1:1000 there are 18 of them, which come in the below-tabulated families, all of which are abundant numbers descending from 6. After the first few terms the members of each family follow the same trajectory to convergence. The final prime via which they converge is termed p_c

aliquot_table6

Aliquot_Monster_values_Figure6Figure 6. The evolution of the first members of each family. f_{840}: dark red f_{138}: cyan; f_{702}: dark blue; f_{720}: dark green; f_{858}: hot pink; f_{936}: gray.

One notices that families f_{138} and f_{858} have a higher-order relationship because they converge via 59. However, we keep them as different families for, barring the last 8 elements of ali(n), they followed very different trajectories (Figure 6). Their p_c is the 6th most common p_c for n=1:1000, with 45 numbers converging via it (Figure 3). However, 12 of them being monster values it is one p_c over-represented in the aliquot sequences attaining monster values. In contrast, the most common p_c in this range 43 (Figure 3) has only a single monster value (936) in this range. ali(840) shows the most monstrous behavior in this range (Figure 6). It reaches a maximum value of the behemoth number: 3463982260143725017429794136098072146586526240388. I felt please on reaching this number and experiencing the magnificence of ali(840) for myself. After that it remains in the high range for while with two prominent peaks before converging after 749 steps. Such a behavior, with a multiplicity of peaks before convergence, is also seen in the other monstrous families (Figure 6).

We wondered if there was any features of these sequences, which allowed their eruptive growth before finally converging. We observed the following:
1) They start as even abundant numbers, which means that they are statistically in the general group of numbers which are going to have longer trajectories to convergence.
2) Their trajectories tend to remain even, which again increases their probability of having a long convergence path. By specifically studying the first major eruptive case ali(138), we see that it has a convergence trajectory of length 179. It remains even from ali(138)[1] to ali(138)[175]. Thus, remaining even is a key factor for a long convergence path.
3) The next key feature observation regarding their growth came from examining the behavior of the first two cases which show above average behavior. These are f(30)=16 and f(102)=19. First, both are even abundant numbers satisfying the above condition. Then we note their behavior under the aliquot map:
ali(30)=30, 42, 54, 66, 78, 90, 144, 259, 45, 33, 15, 9, 4, 3, 1, 0
ali(102)=102, 114, 126, 186, 198, 270, 450, 759, 393, 135, 105, 87, 33, 15, 9, 4, 3, 1, 0
We see that both of them have a run of 7 continuous abundant numbers, which are multiples of the perfect number 6. This allows a monotonic increase. When they lose this divisor 6 in the 8th iteration they become odd and start falling rapidly and converge. We then looked if this pattern might play out in a truly eruptive example by taking the case of ali(138). We see that from ali(138)[1]=138 to ali(138)[30]=1467588, then ali(138)[65]=19406148 to ali(138)[72]=348957876 and again ali(138)[95]=1013592 to ali(138)[117]=100039354704 each number is a multiple of the perfect number 6. The repeated generation of a multiple of a perfect number under the aliquot map means there can be stretches of unhindered growth with one abundant number succeeding the previous one until that perfect number is lost among the divisors. It is the final loss of 6 and then 2 among the divisors that allows ali(138) to converge. In making these observations we had recapitulated Lehmer’s key findings in the context of the growth of the most mysterious class of aliquot sequences we shall talk about next.

There are 12 f[n], for n \le 1000, which could not be determined because the corresponding ali(n) never converged in our computation (the blue dots in Figure 4). A search on the Internet reveals that deep computational efforts by various investigators have not seen an end to these sequences. They belong to 5 families which are known after Lehmer-II who first studied them. Within each family (listed below), after the first few terms the evolution converges to the same trajectory (Figure 7). These families are:
f_{276}=276, 306, 396, 696
f_{552}=552 ,888
f_{564}=564,780
f_{660}=660,828,996
f_{966}=966

Aliquot_Lehmer5_Figure7Figure 7. f_{276}: dark red; f_{552}: dark blue; f_{564}: dark green; f_{660}: hot pink; f_{966}: cyan
All these numbers are abundant numbers descending from 6, which is a tendency they share with the above monster numbers that eventually converge. The frequencies of their largest prime factors are tabulated below:

\begin{tabular}{|r| r|r|r|r|r|r|r|r|r|} \hline p & 7 & 11 & 13 & 17 & 23 & 29 & 37 & 47 & 83 \\ \hline freq & 1 & 2 & 1 & 1 & 4 & 1 & 1 & 1 & 1 \\ \hline \end{tabular}

Notably, in this set except f_{564}, 4 of the five families have a member with 23 as the highest prime factor. It is now conjectured by mathematicians that these define the founding members of a class of aliquot sequences that would never converge but eventually shoot off to infinity. Examining the eruptive growth of these sequences, we found that the same features that cause the eruptive growth of the converging but monster n hold true here too. Thus, if we consider the first case ali(276), which starts with a double of the first monster n=178, we notice that it starts off well with the perfect number 6 as the divisor for the first 5 terms successive terms — ali(276)[1]=276 to ali(276)[5]=1872. But then the sequence loses 6 in the 6th term a stutters for a few terms even going down from the high point it reached. But then in ali(276)[9]=2716 it acquires a new perfect number divisor 28, which drives the abundance of successive terms until the it reaches the giant 28 digit ali(276)[170]=7165455981799192761913565252. Lehmer’s study was the first which noted the role of such persistent divisors in driving up the aliquot sequences. Accordingly, the grand old man of arithmeticians, Richard Guy, called these ‘drivers’ and in addition to 2 and the perfect numbers defined a few more of such. What seems to happen is that in these apparently non-converging aliquot sequences the drivers drive the growth to some large number after which they are lost. But before the sequence can crash by attaining an odd number, a new driver emerges and pushes up its growth again. Thus, these sequences might not converge. On the other hand the case of the monstrous ali(840) with f=749 tells us that even after many such runs there is some chance of hitting a number, which brings you crashing down though its even almost all the way through. Whatever the case, the aliquot sequence of these non-converging numbers tell us that there are several more numbers in their trajectories, which would similarly not converge. Hence, non-convergence will be encountered frequently as the starting numbers get large.

In conclusion, following along the lines of the ancients, we find that the aliquot sequences offer us some philosophical lessons and mysteries:
1) There is the predictable: The primes and perfects display very predictable and uniform behavior.
2) There is the somewhat predictable: like the amicable numbers, for some of which a rule was found as early as Thabit ibn Kurra. But not all of them can be captured by an easy rule.
3) There is the statistically tendency: We know that an even or abundant number is more likely to have a longer path to convergence though it is not clear at all if any rule can say which of them might be monstrous and which rather common place.
4) There is the unpredictable and mysterious: Why are some numbers “aspiring numbers” which converge to a perfect number? Is there any rule to describe them? Why is 43 the preferred prime for convergence at least for n=1:1000. Why do some numbers not converge? Can we predict which numbers will not converge? Do they really not converge at all? As far as I know these remain unanswered. Thus, a very simple arithmetic process gives rise to a whole range of unexpected behavior.

Posted in Heathen thought, Scientific ramblings | Tagged , , , , , , , , , , ,

The ghost in the tattered Gattermann

Vidrum had dropped by to see Somakhya and Lootika when they had just started their household together. They had reconstituted a fairly elaborate lab in the biggest room of their home. They had also completely set up their fire room, which was well-equipped for karman. It had a niche for the images of various deities along with a sacristy. They showed Vidrum around and after uttering some purificatory incantations and, sprinkling water on him from a kamaṇḍalu, led him into the fire-room. There he saw the images of Maghavan along with his parivāra, the six-headed Kumāra, the patron god of Somakhya and Lootika, and of Ucchiṣṭolka and his wife covered in a blue cloth. Thereafter they passed the images of the lord of the yakṣa-s and those of the 7 mothers to finally arrive before the image of the terrifying patron goddess of their ancestors, Atharvaṇa-bhadrakālī. As they stopped before it, Somakhya smeared some vibhūti and kuṃkuma on Vidrum’s forehead from a human calvaria kept before it. There was not much furniture beyond their bike rack and three ample bookshelves for both of them still had their collection of physical books. So they sat on cushions on a floor mat facing those bookshelves.

Vidrum: “I sure you will say that this was bound to happen due to the gods or maybe that it is the way of siddha-s and their kulāṅgaṇā-s or perhaps it might be that two of you were together janman-janman. Whatever the case, I guess you two have to ultimately thank me for having reached this destination in life – I am pretty sure neither of you would have ever spoken to each other had it not been for me…And I hope you will use your mantra-siddhi to aid me to reach a similar destination in life too.”
Somakhya: “Of course Vidrum, we certainly have thank to you.”
Lootika: “We still don’t know how best we should repay you. I would still be in some debt for all the bad things I have said about you. In the least, I hope you would forgive me for that.”
Vidrum smiled and said: “You are forgiven.”
Somakhya: “Though you have forgiven her, don’t be sure it will end with that. You could be at the receiving end in the not so distant future.”
Vidrum: “I’m prepared, though it does appear to me that Lootika has become a more of a good girl over time. In any case Lootika, maybe, I should give you many more chances like Śiśupāla since I know that is your nature. After all, I have not forgotten those early days in school when you told me that you were even jealous of Somakhya. You and your sisters had some ferocity atypical for your sex, though your looks do not betray that. But if someone could hold their own in the domains so peculiar to you it would be Somakhya.”
Lootika controlling a chuckle: “Ouch! But as for being jealous of Somakhya, maybe my steroids got better of me shortly after I told you that.”
Vidrum: “Now don’t tell me it was the steroids since I have heard my friend, your dear Somakhya, remark that such things are ephemeral and in the long run don’t mean much like debris floating on a river. There is perhaps something which is indeed in the realm of those āgamika matters you’ll are known to know.”
Lootika: “But you don’t complete the whole train of physiology…I need not tell you now that there are the steroids and then there is oxytocin. A little unusually amidated peptide can go a long way.”

Vidrum then walked over to their shelves to look at the books and noted a tattered book which had been fortified and inscribed by Lootika along with a daub of kuṃkuma on it. Vidrum: “Gattermann, Heidelberg, 1894. Evidently, this old tattered book is of much value to you Lootika. You have even applied kuṃkuma to it…”
Lootika: “That is not kuṃkuma. That happens to be sulfosalicylic acid’s complex with Fe(III)+ in the famous FeCl3 test. That dark streak below it from a similar complex with salicylic acid. I’m pretty sure the ghost of Gattermann would not have approved of such daubing on your laboratory book, but it was in my earlier days.”
Somakhya: “This was one book she was rather possessive about and did not give it to Varoli who made claim for it.”
Vidrum: “Why so Lootika? Have you not been telling me that such material possessions come and go, ever since when my bike was stolen in school?”
Lootika: “This is special, it was a turning point in my career.”
Vidrum: “How so?”
Lootika: “It is a long story.”
Vidrum: “So be it. Somakhya have you heard it?”
Somakhya: “Not the long form she proclaims. Did not seem anything out of the ordinary.”
Vidrum: “Why don’t you tell us then?”
Lootika: “When we were kids, my father seeing my interest in scientific experimentation had just begun getting me to start a little lab at home and obtained a bunch of chemicals for me. These were the pleasures of Bhārata that a future generation might not have. It was then that I and Vrishchika accompanied our mother to help her haul groceries from the market stalls near our house. After the purchases, we were walking back home when we caught sight of a cart-man who selling the roadside śṛṅgāṭaka with the harimanthaka-sūpa.”
Vidrum: “Ah! that famous śṛṅgāṭaka-seller. My mouth is watering even as you mention it. Eating his śṛṅgāṭaka-s with the chick-pea slurry was one of the high-points of my otherwise dismal youth.”
Somakhya: “We do have some lunch for you. You can see if Lootika might come anywhere near your famed śṛṅgāṭaka and bhṛjjika cart-man of whom I have heard more than once from you. In any case, Lootika continue with your tale for I have not heard all these details either.”

Lootika: “We asked our mother to buy the śṛṅgāṭaka-sūpa for us. She refused as ever barking at us and conjuring up images of various helminthic infections of the brain, Entamoeba, and Balantidium. But all that fell on our deaf ears and we were throwing a tantrum. Our mother stood there and watched to see if the cartman’s procedure was hygienic enough for her standards. Then she suddenly remarked: ‘it is not a bad idea if you get some immunity. The śṛṅgāṭaka-s are bhojya and moderately bhakṣya, so I’ll get you all one each. But not that chickpea side-dish. Instead, I’d substitute it with something at home.’ So she told that vendor that she would take six freshly made śṛṅgāṭaka. He was about to dispense them in pieces of paper which he tore from a book and handed to me and my sister. She forbade him and instructed him to transfer the śṛṅgāṭaka-s directly from his kaṭaha to an empty box in one her bags. Holding that page from the book felt like coming in possession of a Japanese yokāi. In the light of the lantern on the food cart, I caught the printing on the page, which was made of good American paper – it displayed a potash apparatus. Puzzled, I asked I could see the whole book. The cart-man gruffly handed it to me. Leafing through it even as the śṛṅgāṭaka-s were being transferred I realized it was something to possess. I asked my mother if she could buy it from him. My mother gave him a few ₹s extra and got the book for me. That evening eating that śṛṅgāṭaka with my mother’s pickle and reading the very Gattermann, which you just picked off the shelf, I felt I was in the abode of Indra. I wished my mother had bought us at least one more of those śṛṅgāṭaka-s, but she instead also meant to give us another form of immunity. After we were done with dinner, she brought out images of the slices of the brain of a man who died recently. ‘Cysticercosis’ she remarked even as I was shocked to see the ghastly pitted cerebrum. She explained the locations in the brain and where all those lesions were. Then she showed us sections of a liver infected by Entamoeba along with rupture where the amoebae had entered the patient’s lung. Vrishchika was excited beyond words seeing those and made copies which she stored on her computer. I retired to the lab that I had just initiated to do some experiments inspired by Gattermann. When I returned to sleep that night, Vrishchika who lay on the mat beside me was excitedly talking about her readings in parasitology. ”

Vidrum: “I guess just as with you, Vrishchika too was quite formed right then as though you’ll were remembering things from your past births? No doubt she intimated even her seniors in the first week of joining med school with a knowledge of morbid anatomy that exceeded them.”
Lootika: “Well, she was one among us caturbhaginī who always fascinated by morbid anatomy. Past births or not, I mentioned Vrishchika because my proclivities too lay in the direction of biological exploration but I did not get distracted to go along the paths of my sister at that point and applied myself to a year of unrelenting chemical experimentation closely following many of the detailed explanations of the śūlapuruṣa Herr Gattermann. The first big thing I did of my own was to extract a mixture of alkaloids from peyotes, which were growing in the nearby rock-garden. I first basified them with NaOH and then extracted them into xylene. Thereafter, neutralized them with repeated salting steps using acetic acid to form alkaloid acetates and extracted the salts back to water and allowed them to crystallize. Buoyed up with the confidence of this success I went on to conquer separation with thin layer and paper partition chromatography. Then I moved on to isolate a conessine-like alkaloid, which seemed to give some relief to certain people with some gastric disorders. Then I took on the tropanes, which subsequently two of my sisters took over and continued. Of them, it was Varoli who had real talent in this direction. That was around the time we first made acquaintance with you. At the end of that, I returned to biology, now as a biochemist in the making, but I had been transformed in many dimensions.”

Vidrum: “Ah! I can now see how that book holds a special place for you. So Somakhya that seems to have been at the root of the virtuosity of your wife you used to episodically praise in our youth followed by the phrase ‘don’t tell her that I think so’.”
Somakhya: “If you look at Gattermann that would not be apparent at all. It can only inspire an already prepared mind. A mind which is also coordinated with the hands and possessed of a certain patience and an eye which can quickly catch the subtle. However, it is said to have even inspired the great chemist Woodward to scale heights like never before.”
Lootika: “It probably gave some of that Woodwardian inspiration to Varoli. She, more than me, had that ability in pure chemistry and the capacity to combine it with a knowledge of theory like what Somakhya has. This was clear from her early interest and graduation to spectroscopy. For me, it was more of getting the fundamentals straight and thinking quantitatively while doing experiments, which held me in good stead in the years which followed.”
Somakhya: “Sure. Spidery, I think we should not keep our guest waiting from savoring your experiments in the kitchen.”

As they were having lunch, Vidrum remarked: “This is the first time I am eating food cooked by Lootika. Her wonderful spread with milk precipitated with HCl from a burette and the liquid N2 chilled stuff is certainly delightful to the tongue. Somakhya, the gods have been doubly good to you to join you with a wife who can cause delights to the gustatory system. I again reiterate, you as brahmins should intercede on behalf of me to get the gods to be at least 1/10th as good to me.”
Lootika smiled and said: “Again, we should state that you perhaps greatly over-estimate our capacity as the knowers of brahman and I think I should give you another perspective. Somakhya’s father remarked that a man who gets entangled in the good rasa-s of his wife’s food soon heads towards pāpman. Hence, he eschewed indulgence in such, observing a vrata of eating mostly that which hardly inspires the tongue – bitter, bland, tasteless and the like. It is thus that he attained siddhi-s like a mahāvratin.”
Vidrum: “Well, you all are the eternal pessimists.”
Somakhya: “Since we are well aware that in life many things that are seen as the door of pleasure eventually lead to sorrow.”

After lunch, Vidrum again went up to the tattered Gattermann and picking it up closely looked at it. Sniffing at it he turned to his hosts and remarked: “You guys had the capacity to summon all kinds of beings from the beyond. But, you know, due to my long-suffering stay in a dwelling that was stationed not far from the famous cemetery of our youth haunted by more entities than I would care to know, I have become uncannily attuned to them.”
Somakhya: “Truth to be told you are way more attuned to them than any of us. We are in fact practically blind to them except when unveiling them via prayoga-s.”
Vidrum: “I must say this Gattermann seems positively haunted by something. Lootika mentioned that it was like yokāi of the Japanese. I wonder if she knows more than she let out while telling us its story.”
Lootika: “I only meant it in a very colloquial sense. I really have not had much of sense of any haunting in that book.”
Vidrum: “Then guys we must do something we did in our youth. We should ply the planchette to see if we can get him to speak.”
Somakhya: “We don’t have a planchette with us now.”
Vidrum: “I’m sure you can do more. Could you not summon him by some other means.”
Somakhya: “We could, if you are willing to be a medium, do a bhūtadarśana. But the last time I did it you said you never wanted to be one again.”
Vidrum: “That’s OK. I think I am game for it again for I think there is something sinister about this book.”
Lootika: “OK we shall try a Kapālīśa Bhairava-Raktacāmuṇḍā-prayoga to draw the entity to give you a bhūtadarśana.”
Somakhya: “No Lootika! We might need that prayoga soon for something more serious and we do not want to deploy it right now. Since were are sarvādhikārin-s we shall deploy the prayoga of Sahasrāra and Viṣvaksena along with his Karimukha-s to bring out the resident.”

As the prayoga got underway Vidrum felt himself lapsing into a strange trance. He wondered if it was the good meal that he had had in a long time which was making him sleepy or if it was something else. But soon it became clear he was going into a bhautika trance. He felt as though he was in a pleasant theater with a nice perfume watching a movie but like a Saṃjaya he also started speaking out in precise detail all that was playing out before his eyes, which looked even more real than real life:
“I repeatedly hear and visualize the following syllables each in a svara lower than the previous one: pau ro mo go ṣu.

It is a bright morning with the sun shining amidst the coconut trees. The train is headed to the town of Kumbhaghoṇa in the Dravidian country. Among the throng of travelers is a young man who appears to be in his 20s but bears the mien of one who has seen a lot of life. By the ūrdhvapuṇḍra he wears it is clear that he was a member of the northern branch of the dominant vaiṣṇava sect of that part of the country. It seems to be clearly a different era for among the travelers are soldiers with rifles from a bygone time. They are talking about a great rebellion of god-fearing Mohammedans that they have just put down. Keeping with this we also see a couple of English panjandrums with their hats and revolvers – clearly upholders of the English tyranny in the subcontinent. The said vaiṣṇava is seated beside the window and intensely looks out once in a while but for the most part, is immersed in reading a tome titled the ‘On the origin of species…’ Sometimes he raises his head and makes some notes in a notebook. On reaching Kumbhaghoṇa he spills out of the train with his tin box along with a mass of other travelers and heads towards a stand of bullock carts. After choosing a special one which he evidently seemed to have prearranged he heads towards a village some distance from the town. Upon reaching the village he is seen directing the cart-man to one side of it where stands an exceedingly old temple that does not appear to be in particularly active service. Having bought a ghee lamp, some flowers and basil leaves he goes to the temple. There is no priest there nor is are there any other visitors besides him. Having lit the lamp he does a pradakṣiṇa to the deities. As he completes his pradakṣiṇa he is approached by another temple visitor. He respectfully asks the vaiṣṇava: ‘Oh brāhmaṇa, are you the arcaka of this shrine?” He answers: ‘no, I am from the Karṇāṭa country; I’m visiting here.’ The other man: ‘But you seem to be a learned brāhmaṇa, maybe you can answer my question.’ The vaiṣṇava: ‘Maybe, go ahead.’ The other man: ‘I am aware that the deities of the temple are Kṛṣṇa, Rukmiṇi, Balrāma, Pradyumna, and Aniruddha. But who is the fifth male deity? Some say he is Rāma but others say that is not so.’ Our vaiṣṇava says: ‘ You may say so and take it to be this way; but that is not Rukmiṇi, she is devī Ekānaṃśā. That other deity you can take to be Sātyaki. The man:’OK. Who is this Sātyaki?’. The vaiṣṇava: ‘He is an incarnation of the chief Sādhya, a class of gods who formerly carried out the orders of the śrīman Nārāyaṇa. He was an incarnate hero in the days of the Bhārata to aid the līlā-s of incarnate Nārāyaṇa and Nara. You must hear the Bhārata when it is recited by the Bhāratiyār who visit the village. Having said this we see the vaiṣṇava seek a corner of the temple where he is seen doing japa of the mantra:’vavande vāsudevaṃ ca saṃkarṣaṇaṃ ca । namāmi pradyuṃnaṃ sadyojātam aniruddhaṃ ca । ekānaṃśāṃ prapadye sādhyaṃ prapadye । oṃ ॥‘.

Having finished his japa he goes out to wander near the environs of the temple. He walks up to nearby tank that was excavated by a Vijayanagaran general to commemorate his victory over a preta-alliance. The vaiṣṇava is seen collecting some of the green water from it in a container. Stopping near a vast bastard poon tree he closely examines some of its fallen pods and collects a couple into a bag. Returning to the courtyard of the temple he seats himself beside one of the low walls and carefully takes out a brass microscope from a box in his tin case. He sets up some slides and examines the green water he has collected. He thinks to himself: ‘Of all these algae which might be close to the ancestor of the modern land plants? Applying the principles of Mr. Darwin, I believe that somewhere within these silky filamentous forms we should see the origin of land plants. While those which I collected from the sea near Madras have considerable complexity, I doubt they were the ones which gave rise to the land plants for after all from the sea the first transition must have been to fresh water like these forms I’m first seeing. So I must look more closely at these freshwater forms to see if any of them share features specifically with the land plants. Then he makes a slide of a fungus from the pods he had collected and after some examination remarks: ‘This looks like an interesting new species. I will have to study it more closely when I’m back in the college.’ Thus, he is engrossed in his observations. Some a kid with his father passes by the vaiṣṇava. He asks his father:’What is this brāhmaṇa doing?’ The father responds: ‘Let him be, he comes here from time to time to dig dirt and pond scum and look at it through that magical yantra. Don’t ask him anything or he might cast a spell on you.’”

Then Vidrum’s transmission went blank for some time. But he seemed to experience a great quiet and peace with occasionally re-emergence of the syllables he had seen and heard earlier. Lootika remarked to Somakhya: “O Bhṛgūdvaha the Ayyangār seems to have been prescient for his times.” S: “True, dear; I am really curious to know how far he got with his objective.” Then Vidrum’s transmission continued. Vidrum: “I see a man screaming: ‘I am the one, I am the one.’. He looks contorted and with pinpoint pupils as though poisoned by an opioid.”
Lootika: “Yes. He will speak. Don’t worry.”
Vidrum noticed the man freeze for a while and then start speaking: “My name is Sadāhāsa. I belonged to the 3rd varṇa and my people originally came from the Lāṭānarta country. My father ran a grocery shop and I was expected to join in that business. But from an early life, I did not have much proclivity in the direction of my family. After I passed the 10th class with reasonable marks, my father realized that I might be able to get some other means of earning by studying a little more rather than manning the shop. Anyhow my two elder brothers were there to do that. Hence, after some deliberation he let me study further in the science stream in the hope I might become a doctor, a dentist or an engineer. I was never really interested in those professions at all. I just drifted away not knowing what was my true calling and joined the university two years later to obtain a B.Sc. degree in chemistry. My father was unhappy with me continuing with my apparently useless science education and being a drain on his exchequer. I tried to tell him that the degree might give me some knowledge that might help me start a paint shop. It was around that time he was struck down by the rod of the black god Yama. However, my brothers were supportive and as they had opened a new food stall that was meeting with some success; so, they continued to support my education. Thus, I made my way to the M.Sc. program having done tolerably well in the B.Sc course. By some force unknown to me, I became intensely fascinated with organic chemical experimentation in course of this degree and got admission into the Ph.D. program with a stipend in at the university in the dreadful city of Visphoṭaka teeming with all kinds of criminal and debauched elements.

That Ayyangār, whose story I gave you a glimpse of, eventually reached the end of his allotted span of time. As Yama’s dogs with their broad muzzles were about to shred him to pieces, he cried out: “Vāsudeva! Balabhadra! Pradyuṃna! Aniruddha! Ekānaṃśā! and he was borne away to join the vast retinue of Viṣvaksena in the loka known as Vaikuṇṭha. Nobody around him really understood what he had researched and discovered in his life. His best student had only 1/24th of his genius. Before his death, the vaiṣṇava asked him to carefully study that fungus he had discovered on the pods. He never did so but to his credit, he continued to culture it on a bark culture devised by the old Ayyangār. Then he passed it on to his student to do his Ph.D. on that but he made no serious headway beyond continuing to culture it. That student became a lecturer at my university. There was a curious brāhmaṇa student with origins in the Karṇāṭa or Drāviḍā country who was in the bachelors program at that time in his department. He found out that the fungus made a potent cytotoxic compound. This piqued my attention and I decided to determine its structure and try to synthesize it as part of my Ph.D. project. After some effort, I showed that it was a protocatechuate ester derivative of a sesterterpenoid with four sulfurs in a tandem linear linkage.”

Lootika excitedly: “vallabhatama! hear that! the sesterterpenoid with epitetrathio linkage!” Somakhya: “varārohe! does it not have your mind racing? From whence? from whence?”

Vidrum continued the relay undistracted by his friends’ excitement: “Puffed up with my success I decided to use the rest of the time I had on my stipend to attempt a synthesis. It was a tall order and I could not get the epitetrathio linkage and struggled with the heptagonal ring with the oxygen in it. But my successful purification, structure determination and good progress towards the synthesis gave me a respected paper and a fellowship to work upon graduating in Japan. My adviser was jealous of me because he had failed when he applied to the same Japanese fellowship. Also, this cytotoxic compound with a therapeutic potential could bring me some recognition and money. So he decided to thwart me. A couple of years before that point a girl of great beauty but no ability had joined the lab. She was clumsy from day one. She broke an expensive cuvette of the spectrophotometer the first week she was in the lab. She then caused a fire with tert-Butyllithium. But my adviser kept her in the lab for some reason. Perhaps, it was because just like me he too was greatly infatuated by her. Accordingly, I was excited even more than about receiving my Japanese fellowship when she suggested that we spend the weekend at the hotel with some drinks. When I went to use the rest-room she seemed to have slipped a mixture of ganja and opium into my drink. She was doing so under the instructions of our adviser who wished to bring a drug charge on me and thwart my going to Japan. But clumsy as she was, she overdosed the opium and I expired as a consequence. The adviser handed my work to her and she graduated with a Ph.D. for doing nothing. Having passed into the state of a phantom I wanted revenge on them but my vīrya was entirely drained due to the excesses I had engaged in with my killer on the day of my death. Thus, I was consigned to being a benign phantom tied to my favorite book. My brothers had no value for my books sold them to the paper-recycler from whom the śṛṅgāṭaka man obtained it to make his paper cups. It was then that I was recovered by this brāhmaṇa lady here. She and sisters are armed with various mantra-s; hence, I remained incapable of movement as they generally performed powerful digbandha-s to protect themselves. But now good man you have set me free; hence, I’ll take my revenge and come back to do you a good turn.”

Vidrum: “Wow! As in the days of our youth you have managed to make visible a most remarkable phantom!”
Somakhya: “You deserve all the credit for sniffing this one out. Frankly, I did not sense anything there.”
Lootika: “I sort of feel embarrassed that this fellow was lurking all this while much like the hobgoblins in your old house and we could do nothing about it. At least he says he is going to come back to help you.”
Vidrum: “I thought I had seen the last of my goblins but I guess there is more in store.”
Somakhya: “By no means, you have seen the last of them!”

Posted in Heathen thought, Life, Scientific ramblings | Tagged , , , , , ,

The hearts and the intrinsic Cassinian curve of an ellipse

Introduction

This investigation began with our exploration of pedal curves during the vacation following our university entrance exams in the days of our youth. It led to us discovering for ourselves certain interesting heart-shaped curves, which are distinct from the well-known limaçon of Etienne Pascal and its special case the cardioid. It also led us to find the intrinsic relationship between the ellipse and the Cassinian curve that is associated with every ellipse. We detail here those observations with the hindsight of multiple decades and the availability of excellent modern geometric visualization software (in this case Geogebra) since the days of our paper and pencil explorations (However, even then we had an excellent set of ellipse and circle templates that our father had gifted us and also an ellipse drawing tool which we had made inspired by the yavanācārya Proclus). We first lay the ground work with some basic results and concepts that provide the necessary background before delving into the heart of the topic under discussion.

The eccentric circles theorem

Given a circle and a point inside it, the locus of the midpoint of the segment joining the said point to a moving point on the circle is another circle with radius half that of the given circle and with its center as midpoint of the given point and the center of the given circle.

ellipse_excentric_circle_Fig1Figure 1

Let (x,y) be the coordinates of the point P on the given circle with center at origin O (Figure 1) and radius 2a. The coordinates of the given point are F_1=(0, 2c). Let the coordinates of the midpoint M of the segment \overline{F_1P} be (x_1,y_1). From Figure 1 it is clear that:

x_1=\dfrac{x+2c}{2}, y_1=\dfrac{y}{2}; thus x=2x_1-2c, y=2y_1.

By plugging these into the equation of the given circle x^2+y^2=4a^2 we get:

4x_1^2-8cx_1+4c^2+4y_1^2=4a^2

x_1^2-2cx+c^2+y_1^2=a^2

\therefore (x-c)^2+y^2=a^2 \rightarrow \textrm{Locus}(M)

Thus, the locus of M is a circle with A=(0,c) as center and radius of a: Q.E.D.

The ellipse

Given a line d and a point F outside it, what will be the locus of all points such that the ratio of their distances from F and d respectively is a given constant value e_c?

ellipse_conics_Fig2Figure 2

From the solution shown in figure we get the equation of this locus to be:

x^2+(1-e_c^2)y^2-2h(1+e_c^2)y+(1-e_c^2)h^2=0

Being a quadratic curve it will be a conic. Specifically, when e_c<1 it is an ellipse; when e_c>1 it is a hyperbola and when e_c=1 it is a parabola. This relates to why these curves are called conic sections. We can see that the distance from point F can be represented by the surface of an infinite bicone with vertex at F. The distance from line d can be represented by a plane containing d. The given ratio e_c specifies the inclination of this plane such that the angle by which the plane is inclined is \theta=\textrm{arctan}(e_c). The intersection of this plane and the bicone generates the conic section, which when projected on the xy plane appears as the conic curve specified by the above equation (Figure 3).

ellipse_conics_Fig3Figure 3

Thus, when the inclination of the plane is less than \pi/4 it is an ellipse. When it is exactly \pi/4 it is a parabola. When it is between \pi/4 and \pi/2 we get a hyperbola. Corresponding to this are the Greek terms ellipse: less than; para: equal; hyper: greater than. This number e_c=\tan(\theta) (where \theta is the angle of inclination of the generating plane) is the eccentricity of the conic and F is a focus of the conic.

By definition the bipolar equation of an ellipse is r_1+ r_2=2a. Here, r_1,r_2 are the distances of a point on the ellipse from the two foci of the ellipse F_1, F_2. a is the semimajor axis of the ellipse. F_1 is one of the foci of the ellipse ( for instance, as determined by the construction in Figure 2 and 3) then the second focus F_2 is at a distance of 2c from F_1 along the major axis of the ellipse. c= e_c\cdot a. Further, it is easy to see that a^2-c^2=b^2, where b is the semiminor axis of the ellipse.

The eccentric circles of an ellipse

Given an ellipse and a point P moving on it, 1) what is the locus of the foot of the perpendicular dropped from a focus of the ellipse to the tangent at P? (i.e. locus of the intersection of the tangent at P and the line perpendicular to it from one of the foci. 2) What is the locus of the reflection of one of the foci on the tangent drawn to the ellipse at P.

ellipse_excentric_circles_Fig4Figure 4

From Figure 4 it is clear that the \triangle F_1QP \cong \triangle PQR by the SAS test. Hence, \overline{F_1P}=\overline{PR}. By definition of ellipse \overline{F_1P}+\overline{F_2P}=2a. Thus, \overline{PR}+\overline{F_2P}=\overline{F_2R}=2a. Therefore, the locus of R is a circle c_1 with center F_2 and radius 2a.

It is clear from the definition of R that Q is the midpoint (Figure 4) of \overline{F_1R}. Therefore, by the eccentric circle theorem applied to the above-defined circle c_1 the locus of Q is a circle c_2 with radius a and center as the midpoint of F_1, F_2, which is the center of the ellipse. Thus, c_2 is the solution to the problem of the pedal curve of an ellipse with the pedal point as one of the foci. c_2 is also the circumcircle of the given ellipse. These two circles c_1, c_2 are the two eccentric circles of an ellipse.

Construction of an ellipse using its eccentric circles

Since the radii of both eccentric circles of an ellipse are defined by only the semimajor axis of the ellipse, the whole family of ellipses with the same semimajor axis will share the radii of the eccentric circles. Hence, we additionally need to define the foci to construct the ellipse given one or both of its eccentric circles.

ellipse_from_c2_Fig5Figure 5

If we are given just the circumcircle c_2 and a focus F_1 then we can construct the required ellipse thus (Figure 5): Define focus F_1=(-c,0). Draw a segment connecting F_1 to P, a point moving on the circle c_2. Draw a perpendicular line to \overline{F_1P} at P. The envelop of all such lines would be our required ellipse.

ellipse_from_c1c2_Fig6Figure 6

If we are given both eccentric circles c_1 and c_2 then the construction is a little more involved but has interesting consequences (Figure 6). First define the foci F_1=(-c,0), F_2=(c,0). Then draw circle c_2 with origin as center and radius a. Draw circle c_1 with F_1 as center and radius 2a. Let P be a moving point on circle c_2. Join F_1 to P. Draw a line t perpendicular to segment \overline{F_1P} at P. With P as center draw a circle which passes through F_2. This circle cuts the circle c_1 at points A and B. Join F_1 to both A and B. The points where segments \overline{F_1A} and \overline{F_1B} intersect line t are C and D (Figure 6). The locus of points C and D as point P moves on c_2 gives us the required ellipse (blue in Figure 6).

The ellipse hearts

Notably the above construction of an ellipse using both the eccentric circles yields a companion curve (purple in Figure 6). It usually assumes a heart-shaped form with a dimple or a cusp that superficially resembles the limaçon of Etienne Pascal. However, a closer examination reveals that it is not that curve and has a distinct shape; we term it the ellipse-heart because every given ellipse will have its unique ellipse-heart. From Figure 6 we can also see that the ellipse-heart can be defined for a given ellipse as the locus of the reflection of the point of tangency on the pedal line from one of the foci. Like the Descartes oval and its dual the limaçon, this ellipse-heart can be seen as the dual of the ellipse. Its shape can be described by the eccentricity e_c of the ellipse. For high eccentricity it shows a prominent dimple that tends towards a cusp as e_c \to 1. For e_c<\tfrac{1}{2\sqrt{3}} it becomes a convex oval that becomes a circle identical with the ellipse for e_c=0.

In order to derive the equation of this curve, we note that by the above definition of the eccentric circle c_1 we have \overline{AC}=\overline{F_2D}. We also observe (Figure 6) that the ellipse-heart is obtained by subtracting \overline{F_2D} from the radius vector of the eccentric circle c_1. Now, F_2D is itself the radial vector of the ellipse with the focus as the pole. This allows us to define the polar equation of the ellipse using the focus as a pole as is done in celestial mechanics, where one star/planet is at the focus and another star/planet/moon is moving in an elliptical orbit around it. This equation of the ellipse is:

r=\dfrac{\left(a^2-c^2\right)}{a\pm c\cdot\cos\left(\theta\right)}

Here the radial \angle{\theta} is known as the “true anomaly”, as in the definition of elliptical orbits in the planetary theories of Nīlakaṇṭha Somayājin and Johannes Kepler. Given that \overline{AC} \; || \; \overline{F_2D} and in the opposite direction we can derive the equation of the ellipse-heart by subtracting the above radial vector from 2a, the radial vector of the circle c_1 with the appropriate signs. Thus, if the ellipse is:

r=\dfrac{\left(a^2-c^2\right)}{a- c\cdot\cos\left(\theta\right)},

then its ellipse-heart is:

r=2a-\dfrac{\left(a^2-c^2\right)}{a+c\cdot\cos\left(\theta\right)}

While the square of the above equation has an indefinite integral, evaluating it is a bit complicated. Hence, we resorted to the expediency of numerically integrating it and arrived at the area of the ellipse heart A_h to be:

A_h=\pi (4a^2-3ab), where a and b are respectively the semimajor and semiminor axis of the ellipse.

Thus, A_h= A_{c_1}-3A_e, where A_{c_1} is the area of the eccentric circle c_1 and A_e that of the ellipse. Further we also get:

\dfrac{A_h}{A_e}=4\dfrac{a}{b}-3

Thus, when \tfrac{a}{b}=\tfrac{5}{4}, \; e_c=\tfrac{3}{5}, i.e. the three ellipse parameters form a 3-4-5 right triangle then A_h=2\cdot A_e. This is a beautiful configuration (Figure 7). Finally, inspired by the above equation for the ellipse-heart we can also define a second ellipse-heart using parametric equations as:

x=\left(2a-\dfrac{\left(a^2-c^2\right)}{a+c\cos\left(t\right)}\right)\cdot\cos\left(t\right), y=\left(2a-\dfrac{\left(a^2-c^2\right)}{a-c\cos\left(t\right)}\right)\cdot\sin\left(t\right)

This curve has a classic heart-shape (hotpink in Figure 7) for a part of the range of eccentricities of the ellipse. These curves may be considered bifocal like the ellipse, unlike the limaçons (including the cardioid) derived from the unifocal circle. The ellipse and the ellipse-hearts touch each other at the vertices of the ellipse. Figure 7 shows the relationships between a system of ellipses and their corresponding ellipse-hearts. They might define the outlines of certain leaves or the dehisced pod of the bastard poon tree.

ellipse_hearts_Fig7Figure 7

The Cassini curve of an ellipse

Every ellipse is associated with a confocal Cassini curve sharing parameters with the ellipse.

Even though the Cassini curves are well-known, that they are intrinsically associated with every ellipse does not seem to be common knowledge (at least as far as we know). This is despite the historical associations of a version of the Cassini curve, the Cassini oval. Hence, it excited us considerably when, in our youth, we discovered the two to be intimately linked. The curve itself was discovered by the astrologer and mathematician Giovanni Cassini in an interesting context: In the west, as in India, the transition from geocentricity to heliocentricity was neither immediate nor uncontested. Cassini, despite being a prodigious observational astronomer, believed that the sun went around the earth in an oval orbit, which was defined by one lobe of the curve now known as the Cassini ovals. However, later in his life he realized that he was totally wrong and that Kepler was right in describing the orbit of the earth around the sun as an ellipse rather than an oval.

Now, how is the Cassini curve associated with the ellipse? It arises from the following question: Given an ellipse with a point P on it, let points A and B be the feet of the perpendiculars dropped from the two foci of the ellipse F_1, F_2 to the tangent at P. What would be the locus of the points of intersection F and E of the circles with radii r_1=F_1A and r_2=F_2B as P moves along the ellipse. We solved this thus:

ellipse_ovals_Fig8Figure 8

From the above discussion it becomes clear that both A and B will lie on the circumcircle of the ellipse c_2 (Figure 8). As both are pedal points they would define parallel lines \overleftrightarrow{AD} and \overleftrightarrow{BC} which form the rectangle ABCD inscribed in the circle c_2. From this rectangle (Figure 8) it becomes clear that the \overline{AF_1}=\overline{CF_2}=r_1 and \overline{BF_1}=\overline{DF_1} =r_2. We then apply the well-known Euclidean intersecting chords theorem on AD and the major axis of the ellipse V_1V_2. Thus we get:

r_1\cdot r_2=\overline{V1F_1}\cdot \overline{V2F_2}=(a-c)(a+c)=a^2-c^2=b^2

Thus, the product of the two pedal segments of an ellipse is a constant equal to the square of the semiminor axis: r_1\cdot r_2=b^2. Now, the bipolar equation of the form r_1\cdot r_2=b^2 defines the Cassini curve. From this bipolar equation we can derive its Cartesian equation:

\left((x - c)^2 + y^2 \right) \left((x + c)^2 + y^2\right) = (a^2 - c^2)^2=b^4

ellipse_lemniscate_Fig9Figure 9

The form taken by the Cassini curve depends on the eccentricity of the ellipse. When e_c=0, the ellipse, circumcircle c_2 and the Cassini curve all become a coincident circle. When e_c=\tfrac{1}{\sqrt{2}}, the curve crosses over to become the lemniscate of Bernoulli (Figure 9). When 1>e_c> \tfrac{1}{\sqrt{2}} it becomes two separate oval loops and is the classic Cassinian oval. When \tfrac{1}{\sqrt{2}}>e_c>\tfrac{1}{\sqrt{3}} the curve is bilobed with central dimples but a single loop. When e_c \le \tfrac{1}{\sqrt{3}}, the curve takes the form of a single biaxially symmetric convex oval. For values close to the minimum of the range of e_c the Cassini curve approximates a single circle while close to the maximum it approximates two small circles. In conclusion, the eccentricity of the ellipse e_c is entirely sufficient describe the range of shapes adopted by the Cassini curve. Indeed, we can conceive, the three curves, namely the ellipse circumcircle c_2, the ellipse and the corresponding Cassini curve as three degrees of response to the eccentricity parameter. The circle c_2 represents the 0{th} degree in that it does not change at all with e_c. The ellipse represents the first degree response in that in flattens uniformly along the minor axis with increasing e_c. The Cassini curve represents the even more exaggerated second degree response in that it starts of by flattening along the minor axis even more rapidly than the ellipse. Thus it first dimples, then crosses over as the lemniscate and finally breaks apart into the two loops of the oval. Thus the first degree response is a conic while the second degree response is a toric section (i.e. a section through the torus as the Cassini curves). Figure 10 shows an animation of the evolving curve with changing e_c.

ellipse_animation_fig10Figure 10

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