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John von Neumann, the Mathematician

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<strong>John</strong> <strong>von</strong> <strong>Neumann</strong>,<br />

<strong>the</strong> Ma<strong>the</strong>matician<br />

DOMOKOS SZÁSZ<br />

Imagine a poll to choose <strong>the</strong> best-known ma<strong>the</strong>matician of <strong>the</strong> twentieth century. No doubt <strong>the</strong> winner<br />

would be <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>. Reasons are seen, for instance, in <strong>the</strong> title of <strong>the</strong> excellent biography [M]<br />

by Macrae: <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>. The Scientific Genius who Pioneered <strong>the</strong> Modern Computer, Game<br />

Theory, Nuclear Deterrence, and Much More. Indeed, he was a fundamental figure not only in<br />

designing modern computers but also in defining <strong>the</strong>ir place in society and envisioning <strong>the</strong>ir potential.<br />

His minimax <strong>the</strong>orem, <strong>the</strong> first <strong>the</strong>orem of game <strong>the</strong>ory, and later his equilibrium model of economy,<br />

essentially inaugurated <strong>the</strong> new science of ma<strong>the</strong>matical economics. He played an important role in<br />

<strong>the</strong> development of <strong>the</strong> atomic bomb. However, behind all <strong>the</strong>se, he was a brilliant ma<strong>the</strong>matician. My<br />

goal here is to concentrate on his development and achievements as a ma<strong>the</strong>matician and <strong>the</strong> evolution<br />

of his ma<strong>the</strong>matical interests.<br />

The Years in Hungary (1903-1921)<br />

In 1802, <strong>the</strong> Hungarian ma<strong>the</strong>matician János Bolyai was<br />

born in Kolozsvár (called Cluj today). János Bolyai was<br />

<strong>the</strong> first Hungarian ma<strong>the</strong>matician, maybe <strong>the</strong> first Hungarian<br />

scholar, of world rank. His non-euclidean hyperbolic<br />

geometry, also discovered at <strong>the</strong> same time independently by<br />

<strong>the</strong> Russian ma<strong>the</strong>matician Lobachevsky, is now everywhere<br />

recognized, but could not be appreciated in his time in<br />

Hungary. He never had a job as a ma<strong>the</strong>matician. In <strong>the</strong> early<br />

nineteenth century, Hungary was in <strong>the</strong> hinterlands of world<br />

ma<strong>the</strong>matics.<br />

A century later, <strong>John</strong> <strong>von</strong> <strong>Neumann</strong> was born as <strong>Neumann</strong><br />

János on December 28, 1903, in Budapest. His family<br />

belonged to <strong>the</strong> cultural elite of <strong>the</strong> city. Not only were<br />

both of his parents’ families quite well-to-do, <strong>the</strong>y understood<br />

how to use <strong>the</strong>ir wealth to live a rich and complete<br />

human life. But beyond all this, Hungary had changed<br />

dramatically during <strong>the</strong> 101 years since Bolyai’s birth. In<br />

1832, János Bolyai’s discovery was not understood by<br />

anyone in <strong>the</strong> country, except for his fa<strong>the</strong>r. In contrast,<br />

János <strong>Neumann</strong>’s exceptional talent was discovered very<br />

early and was nurtured by top ma<strong>the</strong>maticians on such a<br />

level that it is hard to imagine better circumstances for a<br />

prodigy in any o<strong>the</strong>r part of <strong>the</strong> world.<br />

Much has been written on <strong>the</strong> life of <strong>Neumann</strong> and his<br />

achievements. I have used extensively Norman Macrae’s<br />

exciting biography [M], which I recommend for <strong>the</strong> general<br />

reader. For <strong>the</strong> ma<strong>the</strong>matician, I recommend <strong>the</strong><br />

special issue 3 of Volume 64 (1958) of <strong>the</strong> Bulletin of <strong>the</strong><br />

American Ma<strong>the</strong>matical Society dedicated to <strong>von</strong> <strong>Neumann</strong><br />

shortly after his death. In this issue, first of all,<br />

Stanisław Ulam, a lifelong friend and collaborator of<br />

<strong>John</strong>ny, as he was called by his friends, gives a brief<br />

biography and concise ma<strong>the</strong>matical overview (see also<br />

Ulam’s autobiography Adventures of a Ma<strong>the</strong>matician).<br />

After this introductory paper, world experts in various<br />

fields place <strong>von</strong> <strong>Neumann</strong>’s achievements in a wider<br />

context. Excellent papers with a similar aim also<br />

appeared in <strong>the</strong> Hungarian periodical Matematikai Lapok,<br />

unfortunately in Hungarian only. I also mention <strong>the</strong> book<br />

of W. Aspray <strong>John</strong> <strong>von</strong> <strong>Neumann</strong> and <strong>the</strong> origins of<br />

Modern Computing [A]. I note that <strong>von</strong> <strong>Neumann</strong>’s works<br />

were edited by A. H. Taub [T]. A selection was edited by<br />

F. Bródy and T. Vámos [BV].<br />

<strong>Neumann</strong>’s fa<strong>the</strong>r, <strong>Neumann</strong> Miksa (Max <strong>Neumann</strong>),<br />

a doctor of law, prospered as a lawyer for a bank. ‘‘He<br />

was a debonair, fourth-generation-or-earlier, non-practicing<br />

Hungarian Jew, with a fine education in a Catholic<br />

Research supported by <strong>the</strong> Hungarian National Foundation for Scientific Research grants No. T 046187, K 71693, NK 63066, and TS 049835. This article is a version of<br />

<strong>the</strong> author’s speech at <strong>the</strong> conference in memory of <strong>John</strong> <strong>von</strong> <strong>Neumann</strong> held in Budapest, October 2003.<br />

Ó 2011 Springer Science+Business Media, LLC<br />

DOI 10.1007/s00283-011-9223-6


provincial high-school. He was well attuned to fin-de-siècle<br />

Austria-Hungary and indeed to being a lively intellectual in<br />

any age. His party piece was to compose two-line ditties<br />

about <strong>the</strong> latest vicissitudes of his personal or business life,<br />

and about national and international politics.’’ 1 Jacob Kann,<br />

<strong>Neumann</strong>’s grandfa<strong>the</strong>r through his mo<strong>the</strong>r Kann Margit<br />

(Margaret Kann), ‘‘was a distinctly prosperous man. With a<br />

partner, he had built up in Budapest a thriving business in<br />

agricultural equipment that grew even faster in 1880-1914<br />

than Hungary’s <strong>the</strong>n soaring GNP.’’ The Kanns owned a<br />

ra<strong>the</strong>r big and nice house close to <strong>the</strong> Hungarian Parliament<br />

on <strong>the</strong> so-called Kiskörút, Small Boulevard. The<br />

Kanns and later <strong>the</strong> families of <strong>the</strong>ir four daughters lived<br />

<strong>the</strong>re, while <strong>the</strong> ground floor was occupied by <strong>the</strong> firm<br />

Kann-Heller. When <strong>the</strong> families grew larger, <strong>the</strong>y also<br />

rented <strong>the</strong> neighboring house. János’s mo<strong>the</strong>r Margit was<br />

‘‘a mo<strong>the</strong>r hen tending her children and protecting <strong>the</strong>m.<br />

She was a family woman, a good deal less rigorous than her<br />

husband, artistically inclined, a wafer-thin and later chainsmoking<br />

enthusiast for comporting oneself with what she<br />

called ‘elegance’ (which later became <strong>Neumann</strong>’s highest<br />

term of praise for neat ma<strong>the</strong>matical calculations such as<br />

<strong>the</strong> ones that made <strong>the</strong> H-bomb possible).’’<br />

Max and Margaret had three children, of which <strong>John</strong>ny<br />

was <strong>the</strong> oldest. ‘‘Grandfa<strong>the</strong>r Jacob Kann had gone straight<br />

.........................................................................<br />

AUTHOR<br />

DOMOKOS SZÁSZ is a student of A.<br />

Prékopa, A. Rényi, B. V. Gnedenko, and Ya.<br />

G. Sinai. He founded <strong>the</strong> Budapest schools in<br />

ma<strong>the</strong>matical statistical physics and dynamical<br />

systems. His current ambition is <strong>the</strong> rigorous<br />

derivation of laws of statistical physics<br />

(diffusion, heat conduction) from microscopic<br />

assumptions. His o<strong>the</strong>r enthusiasms are his<br />

family (three children, two grandchildren),<br />

culture, and skiing.<br />

Ma<strong>the</strong>matical Institute<br />

Budapest University of Technology and<br />

Economics<br />

H-1111 Budapest<br />

Hungary<br />

from commercial high school into founding his business,<br />

but he proved demonic in his capacity for arithmetic<br />

manipulation. He could add in his head monstrous columns<br />

of numbers or multiply mentally two numbers in <strong>the</strong><br />

thousands or even millions. The six-year-old <strong>John</strong>ny would<br />

laboriously perform <strong>the</strong> computations with pencil and<br />

paper, and announce with glee that Grandfa<strong>the</strong>r had been<br />

absolutely on <strong>the</strong> mark. Later <strong>John</strong>ny himself was known<br />

for his facility in mental computation, but he had long<br />

before persuaded himself that he could never match<br />

Jacob’s level of multiplication skill.’’<br />

‘‘Nursemaids, governesses and preschool teachers were<br />

an integral part of upper-middle-class European households<br />

in those days, especially in countries where (as in<br />

Hungary) children in such families did not start school until<br />

age ten. As <strong>the</strong> Kann grandchildren and some of <strong>John</strong>ny’s<br />

second cousins came along, <strong>the</strong> building on <strong>the</strong> Small<br />

Boulevard became an educational institution in its own<br />

right. There was an especially early emphasis on learning<br />

foreign languages. Fa<strong>the</strong>r Max thought that youngsters who<br />

spoke only Hungarian would not merely fail in <strong>the</strong> Central<br />

Europe <strong>the</strong>n darkening around <strong>the</strong>m, <strong>the</strong>y might not even<br />

survive.’’ So <strong>John</strong>ny (or Jancsi in Hungarian) learned German,<br />

French, English, and Italian from various governesses<br />

from abroad. <strong>John</strong>ny later told colleagues in Princeton that<br />

as a six-year-old he would converse with his fa<strong>the</strong>r in<br />

classical Greek. This seems to have been a joke, but his<br />

knowledge of languages was real. It not only made his<br />

communication easier in Germany, Zürich, and in <strong>the</strong> US,<br />

but it may have imprinted at an early age axiomatic and<br />

abstract, algorithmic thinking into his brain.<br />

In such an environment, young <strong>John</strong>ny was easily<br />

drinking in <strong>the</strong> knowledge surrounding him. One of his<br />

special interests was history: The family bought ‘‘an entire<br />

library, whose centerpiece was <strong>the</strong> Allgemeine Geschichte<br />

by Wilhelm Oncken. <strong>John</strong>ny ploughed through all fortyfour<br />

volumes. Bro<strong>the</strong>r Michael was confounded by <strong>the</strong> fact<br />

that what <strong>John</strong>ny read, <strong>John</strong>ny remembered. Decades later<br />

friends were startled to discover that he remembered still.’’<br />

Between 1914 and 1921, <strong>John</strong>ny attended <strong>the</strong> Lu<strong>the</strong>ran<br />

Gymnasium in Budapest. Here, too, he received a superb<br />

education. This was made possible by <strong>the</strong> fast economic<br />

and social progress after <strong>the</strong> compromise with Austria 2 and<br />

subsequent cultural and educational reforms. 3<br />

1 Here and below, many unattributed quotes are from [M].<br />

2 Some data from <strong>the</strong> late nineteenth-century history of Hungary. 1867: Appeasement with Austria and <strong>the</strong> formation of <strong>the</strong> Austro-Hungarian Monarchy after <strong>the</strong><br />

defeat of <strong>the</strong> 1848 revolution. 1873: Formation of <strong>the</strong> city Budapest from smaller cities such as Buda and Pest. In <strong>the</strong> years afterward, Hungary and Budapest<br />

experienced extremely fast economic, social, and intellectual progress. Society was quite open, with ‘‘a flood of Jewish immigration into Hungary in <strong>the</strong> 1880s and<br />

1890s as <strong>the</strong>re was simultaneously to New York.’’ In 1896 a World Exposition was held in Budapest also commemorating <strong>the</strong> arrival of Hungarians to <strong>the</strong> Carpathians<br />

in 896. Hausmann-like reconstruction of <strong>the</strong> city contributed to its present character. For instance, <strong>the</strong> first subway of <strong>the</strong> European continent was inaugurated in 1896<br />

in Budapest. ‘‘In 1903 <strong>the</strong> Elisabeth Bridge over <strong>the</strong> Danube was <strong>the</strong> longest single span bridge in <strong>the</strong> world.’’ For <strong>the</strong> interested reader I strongly recommend <strong>the</strong> book<br />

of <strong>John</strong> Lukacs [Luk].<br />

3 Some data from <strong>the</strong> nineteenth-century cultural progress of Hungary. End of nineteenth and first half of twentieth century: Development of national thought and<br />

nationalistic institutions, in particular, <strong>the</strong> foundation of <strong>the</strong> National Museum and <strong>the</strong> Hungarian Academy of Sciences. After <strong>the</strong> Appeasement of 1867, <strong>the</strong> educational<br />

system was transformed and modernized. (For some time <strong>the</strong> Minister of Education was Loránd Eötvös, <strong>the</strong> famous physicist, inventor of <strong>the</strong> torsion pendulum). The<br />

Gazette of Sciences, called today World of Nature, was founded in 1869, that is, in <strong>the</strong> same year as <strong>the</strong> magazine Nature in Britain! The Ma<strong>the</strong>matical and Physical<br />

Society was founded in 1891. (Since 1947 <strong>the</strong>re are separate societies for Ma<strong>the</strong>matics and Physics, called <strong>the</strong> János Bolyai and <strong>the</strong> Loránd Eötvös Societies,<br />

respectively; in 1968 <strong>the</strong> <strong>John</strong> <strong>von</strong> <strong>Neumann</strong> Computer Society was founded.) In 1894 Dániel Arany founded <strong>the</strong> Középiskolai Matematikai Lapok, <strong>the</strong> oldest journal for<br />

high-school students; this journal still flourishes in an extended form including physics. In <strong>the</strong> same year 1894, <strong>the</strong> first Ma<strong>the</strong>matical and Physical Competitions started<br />

(today <strong>the</strong> ma<strong>the</strong>matical competitions are called József Kürschák Competitions).<br />

THE MATHEMATICAL INTELLIGENCER


As a result of <strong>the</strong>se reforms <strong>the</strong> whole educational system<br />

was strong; for <strong>the</strong> talented (and let us also add,<br />

wealthy) pupils, <strong>the</strong>re were élite high-schools. One of <strong>the</strong>m<br />

was <strong>the</strong> Lu<strong>the</strong>ran Gymnasium. It was quite liberal and had<br />

a number of Jewish pupils. Nobel Prize winners E. Wigner<br />

and later J. Harsányi also attended this high-school. As a<br />

matter of fact, Wigner studied a year above <strong>Neumann</strong>, and<br />

already at school a respect and a friendship were formed<br />

between <strong>the</strong> two.<br />

<strong>John</strong>ny’s teacher of ma<strong>the</strong>matics was <strong>the</strong> celebrated László<br />

Rátz. Between 1896 and 1914, he was <strong>the</strong> chief editor of <strong>the</strong><br />

high-school journal Középiskolai Matematikai Lapok. ‘‘Wigner<br />

and o<strong>the</strong>rs recall that Rátz’s recognition of <strong>John</strong>ny’s<br />

ma<strong>the</strong>matical talent was instant.’’ Rátz agreed with Max <strong>Neumann</strong><br />

that <strong>John</strong>ny would be supervised by professional<br />

ma<strong>the</strong>maticians from <strong>the</strong> universities. Thus Professor J. Kurschak<br />

(Kürschák József) from Technical University arranged<br />

that <strong>John</strong>ny would be tutored by <strong>the</strong> young G. Szego (Szeg}o<br />

Gábor) in 1915–1916. Later he was also taught by M. Fekete<br />

(Fekete Mihály) and Leopold Fejér (FejérLipót), and could<br />

also talk to A. Haar (Haar Alfréd) and Frédéric Riesz (Riesz<br />

Frigyes). All in all, <strong>the</strong> prodigy received education and<br />

supervision on <strong>the</strong> highest professional and intellectual level.<br />

In <strong>the</strong> years 1919–1921, when <strong>von</strong> <strong>Neumann</strong> graduated<br />

from <strong>the</strong> Lu<strong>the</strong>ran Gymnasium, <strong>the</strong> ma<strong>the</strong>matical competition<br />

for secondary schools did not take place because of<br />

<strong>the</strong> revolution in Hungary; but in 1918, <strong>Neumann</strong> was<br />

permitted to sit in as an unofficial participant, and would<br />

have won <strong>the</strong> first prize. The list of winners of <strong>the</strong> ma<strong>the</strong>matical<br />

competitions before 1928 include among o<strong>the</strong>rs L.<br />

Fejér, Th. <strong>von</strong> Kármán, D. Konig, A. Haar, M. Riesz, G.<br />

Szego, and E. Teller, whereas L. Szilárd won a second prize.<br />

It is commonplace that around and shortly after <strong>the</strong> turn<br />

of <strong>the</strong> nineteenth and twentieth centuries Hungary exported<br />

a tremendous amount of brains to <strong>the</strong> West besides <strong>von</strong><br />

<strong>Neumann</strong>, but it may be worth listing some of <strong>the</strong>se scientists:<br />

Dennis Gabor (Gábor Dénes; Nobel Prize 1971),<br />

<strong>John</strong> Harsányi (Harsányi János; Nobel Prize 1994), Georg<br />

<strong>von</strong> Hevesy (Hevesy György; Nobel Prize 1943), Theodore<br />

<strong>von</strong> Kármán (KármánTódor), Nicholas Kurti (Kürti Miklós),<br />

Cornelius Lanczos (Lánczos Kornél), Peter Lax (Lax Péter;<br />

Wolf Prize 1987), George Olah (Oláh György; Nobel Prize<br />

1994), Michael Polanyi (Polányi Mihály), George Pólya<br />

(Pólya György), Gabor Szego (Szeg}o Gábor), Albert Szent-<br />

Györgyi (Szent-Györgyi Albert; Nobel Prize 1937), Leo<br />

Szilárd (Szilárd Leó), Edward Teller (Teller Ede), Eugene<br />

Wigner (Wigner Jenö; Nobel Prize 1963), and Aurel Friedrich<br />

Wintner. One might wonder about <strong>the</strong> ‘‘<strong>von</strong>’’s figuring<br />

in several of <strong>the</strong>se names. Macrae explains <strong>the</strong> case of<br />

<strong>Neumann</strong>: ‘‘In 1913 <strong>the</strong> forty-three-year-old Max was<br />

rewarded for his services to <strong>the</strong> government: he received<br />

<strong>the</strong> noble placename Margittai with hereditary nobility, so<br />

that in German he and his descendants could be called ‘<strong>von</strong><br />

<strong>Neumann</strong>.’ Ennoblement was not an unusual award for<br />

prominent bankers and industrialists during those last years<br />

of <strong>the</strong> Austro-Hungarian Empire. Many of <strong>the</strong> 220 Hungarian<br />

Jewish families who were ennobled in 1900–1914<br />

(vs. just over half of that number in <strong>the</strong> whole century<br />

before) hastened to change <strong>the</strong>ir names. Ennoblement was<br />

a way through which one could seize <strong>the</strong> chance to call<br />

The house on Kiskörút today. (Photo by Domokos Szász)<br />

himself less Jewish. Max <strong>Neumann</strong> deliberately did not<br />

change his name.’’<br />

The Ma<strong>the</strong>matics of <strong>John</strong> <strong>von</strong> <strong>Neumann</strong><br />

My aim here should certainly be quite modest, and I can go<br />

into a detailed description nei<strong>the</strong>r of his achievements nor<br />

of <strong>the</strong>ir influence. My goal is to follow some of <strong>the</strong> main<br />

and continuing interests of <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>. The<br />

selection of <strong>the</strong>se interests is subjective and reflects my<br />

knowledge and judgement.<br />

Despite <strong>the</strong> breadth of his interests, <strong>the</strong> picture is not as<br />

complicated as it looks at first glance. This is especially true<br />

for <strong>the</strong> years before <strong>the</strong> War. It seems he usually had one<br />

main interest, and thought about o<strong>the</strong>r problems with <strong>the</strong><br />

left hand, so to speak. This does not mean that <strong>the</strong> o<strong>the</strong>r<br />

results are less important, only that even a genius is subject<br />

to laws of nature. If one wants to reach repeated breakthroughs<br />

in a problem or more than one (cf. Poincaré),<br />

<strong>the</strong>n a necessary condition is full concentration on it for<br />

quite a period. In short, <strong>the</strong> genius is known both by <strong>the</strong><br />

difficulty of <strong>the</strong> problems he can solve with full concentration,<br />

and by <strong>the</strong> difficulty of <strong>the</strong> problems he can solve<br />

with perhaps less persistent concentration.<br />

Axiomatic Set Theory<br />

In <strong>the</strong> first part of this paper I emphasized that this exceptional<br />

prodigy received an optimal launch in Hungary. In<br />

addition, one should note that <strong>the</strong> excellent ma<strong>the</strong>matical<br />

support in Budapest ensured his start as a scholar and as a<br />

researcher. Apart from his first paper with Fekete, his big<br />

interest was <strong>the</strong> axiomatization of set <strong>the</strong>ory. It is most likely<br />

that he heard about this problem from a tutor in Budapest.<br />

Julius König (König Gyula) (<strong>the</strong> fa<strong>the</strong>r of <strong>the</strong> graph-<strong>the</strong>oretician<br />

Denes König (König Dénes)) was himself also working<br />

on set <strong>the</strong>ory, and in particular on <strong>the</strong> continuum hypo<strong>the</strong>sis,<br />

but he died in 1913, before <strong>Neumann</strong> entered high-school.<br />

Anyway, ma<strong>the</strong>maticians in Budapest were definitely aware<br />

of this circle of problems (J. Kurschak, <strong>Neumann</strong>’s mentor,<br />

for instance, was a colleague of J. König). Macrae writes:<br />

‘‘The second of <strong>John</strong>ny’s papers (about transfinite ordinals)<br />

had been prepared while he was still in high-school in 1921,<br />

although it was not published until 1923’’(see [vN23]).<br />

Ó 2011 Springer Science+Business Media, LLC


The young <strong>Neumann</strong> János. (Photo from http://www.ysfine.<br />

com.wigner/neum/ymath.jpeg)<br />

His papers on set <strong>the</strong>ory and logic were published in<br />

1923 (1), 1925 (1), 1927 (1), 1928 (2), 1929 (1), and 1931<br />

(2). It is known that when he read about Gödel’s undecidability<br />

<strong>the</strong>orem in 1931, he dropped thinking seriously<br />

about this field. But <strong>the</strong>re was ano<strong>the</strong>r reason for that, too:<br />

starting at <strong>the</strong> latest from his scholarship in Göttingen in<br />

1926, his main interest had changed: it became centered<br />

around laying down <strong>the</strong> ma<strong>the</strong>matical foundations of<br />

quantum mechanics and hence around functional analysis.<br />

Ma<strong>the</strong>matical Foundations of Quantum Physics<br />

Hilbert certainly heard about <strong>the</strong> Hungarian Wunderkind<br />

quite early, and highly respected his results on set <strong>the</strong>ory and<br />

on Hilbert’s proof <strong>the</strong>ory. But in <strong>the</strong> mid-twenties, and very<br />

much in Göttingen, quantum mechanics was in <strong>the</strong> center of<br />

attention. Hilbert himself was strongly attracted to this disputed<br />

science. One should not forget that Göttingen was a<br />

center of quantum mechanics: Max Born (Nobel Prize 1954)<br />

and J. Franck (Nobel Prize 1925) were professors <strong>the</strong>re<br />

between 1921 and 1933 and between 1920 and 1933,<br />

respectively, and W. Heisenberg (Nobel Prize 1932) and W.<br />

Pauli (Nobel Prize 1945) also spent some years <strong>the</strong>re. In 1927,<br />

a long and important paper [HNvN27] on foundations of<br />

quantum mechanics of <strong>Neumann</strong> with Hilbert and L. Nordheim<br />

appeared. It also formulated a program that was later<br />

carried out in <strong>von</strong> <strong>Neumann</strong>’s book [vN32b].<br />

The program became a success story in many ways. It<br />

meant a victory for <strong>the</strong> Hilbert-space approach. Moreover,<br />

it attracted <strong>the</strong> attention of ma<strong>the</strong>maticians to <strong>the</strong> <strong>the</strong>ory of<br />

operators and to functional analysis. Also, by translating <strong>the</strong><br />

problems of quantum physics to <strong>the</strong> language of ma<strong>the</strong>matics,<br />

it formulated intriguing questions, which ei<strong>the</strong>r<br />

arose in physics or were generated by <strong>the</strong>m by <strong>the</strong> usual<br />

process of ma<strong>the</strong>matics. A substantial result of <strong>von</strong> <strong>Neumann</strong><br />

was <strong>the</strong> spectral <strong>the</strong>ory of unbounded operators,<br />

generalizing that given by Hilbert for bounded operators.<br />

Also, <strong>the</strong> language of operator <strong>the</strong>ory helped to reconcile<br />

<strong>the</strong> complementary and—apparently contradictory—<br />

approaches of Heisenberg and of Schrödinger.<br />

Von <strong>Neumann</strong>’s papers on <strong>the</strong> ma<strong>the</strong>matical foundations<br />

of quantum mechanics and functional analysis appeared in<br />

1927 (4), 1928 (5), 1929 (6), 1931 (2), 1932 (2), 1934 (2),<br />

1935 (3), and 1936 (1). I add that physicists appreciate, in<br />

particular, his <strong>the</strong>ories of hidden variables (more exactly, his<br />

proof of <strong>the</strong>ir nonexistence), of quantum logic, and of <strong>the</strong><br />

measuring process (cf. Geszti’s article in [BV]). From <strong>the</strong><br />

physical and also from gnoseological point of view I stress<br />

his disproof of <strong>the</strong> existence of hidden variables. The laws<br />

of quantum physics are by <strong>the</strong>ir very nature stochastic,<br />

basically contrary to <strong>the</strong> deterministic Laplacian view of <strong>the</strong><br />

universe. Several scholars, including Albert Einstein (his<br />

saying ‘‘God does not throw dice’’ became famous), did not<br />

accept a nondeterministic universe. There was a belief that<br />

probabilistic laws are always superficial and that behind<br />

<strong>the</strong>m <strong>the</strong>re must be some hidden variables, by <strong>the</strong> use of<br />

which <strong>the</strong> world becomes deterministic. This belief was<br />

irreversibly repudiated by <strong>von</strong> <strong>Neumann</strong>. 4<br />

Von <strong>Neumann</strong> writes in 1947 in an article entitled The<br />

Ma<strong>the</strong>matician [vN47], ‘‘It is undeniable that some of <strong>the</strong><br />

best inspirations of ma<strong>the</strong>matics—in those parts of it which<br />

are as pure ma<strong>the</strong>matics as one can imagine—have come<br />

from <strong>the</strong> natural sciences.’’ It is certainly undeniable that<br />

having shown ‘‘his lion’s claws’’ in set <strong>the</strong>ory, <strong>Neumann</strong> got<br />

to <strong>the</strong> right place: To elaborate <strong>the</strong> ma<strong>the</strong>matical foundations<br />

of quantum mechanics was <strong>the</strong> best imaginable<br />

challenge for <strong>the</strong> young genius. The completion of this task<br />

led to a victorious period for functional analysis, <strong>the</strong> <strong>the</strong>ory<br />

of unbounded operators. Von <strong>Neumann</strong> kept up this<br />

interest until his death. Peter Lax remembers, ‘‘I recall how<br />

pleased and excited <strong>Neumann</strong> was in 1953 when he<br />

learned of Kato’s proof of <strong>the</strong> self-adjointness of <strong>the</strong><br />

Schrödinger operator for <strong>the</strong> helium atom.’’ [Lax].<br />

Von <strong>Neumann</strong>, being a true ma<strong>the</strong>matician, was also<br />

aware of <strong>the</strong> o<strong>the</strong>r fundamental motivation of a ma<strong>the</strong>matician.<br />

In <strong>the</strong> same 1947 article [27] he starts, ‘‘I think it is a<br />

relatively good approximation to truth ... that ma<strong>the</strong>matical<br />

ideas originate in empirics, although <strong>the</strong> genealogy is<br />

sometimes long and obscure.’’ Then he continues, ‘‘But,<br />

once <strong>the</strong>y are so conceived, <strong>the</strong> subject begins to live a<br />

peculiar life of his own and is better compared to a creative<br />

one, governed by almost entirely aes<strong>the</strong>tical motivations,<br />

than to anything else and, in particular, to an empirical science.’’<br />

I can not resist adding one more idea of <strong>von</strong><br />

<strong>Neumann</strong> about his favourite criterion of elegance: ‘‘One<br />

expects from a ma<strong>the</strong>matical <strong>the</strong>orem or from a ma<strong>the</strong>matical<br />

<strong>the</strong>ory not only to describe and to classify in a simple<br />

and elegant way numerous and a priori special cases. One<br />

also expects ‘elegance’ in its ‘architectural’ structural<br />

makeup. Ease in stating <strong>the</strong> problem, great difficulty in<br />

getting hold of it and in all attempts at approaching it, <strong>the</strong>n<br />

again some very surprising twist by which <strong>the</strong> approach<br />

becomes easy, etc. Also, if <strong>the</strong> deductions are lengthy or<br />

4<br />

I learnt from Peter Lax that <strong>von</strong> <strong>Neumann</strong> made a subtle error about hidden variables. It was fixed up by S. Kochen and E. P. Specker in J. of Math.& Mech. 17 (1967),<br />

59-87. Editor’s note: This issue remains contentious, and will be revisited in a future issue of The Ma<strong>the</strong>matical Intelligencer.<br />

THE MATHEMATICAL INTELLIGENCER


complicated, <strong>the</strong>re should be some simple general principle<br />

involved, which ‘explains’ <strong>the</strong> complications and detours,<br />

reduces <strong>the</strong> apparent arbitrariness to a few simple guiding<br />

motivations, etc.’’<br />

<strong>von</strong> <strong>Neumann</strong> Algebras<br />

In <strong>von</strong> <strong>Neumann</strong>’s hands, operator <strong>the</strong>ory started to live an<br />

independent life in 1929. In that year he published a long<br />

paper [vN29] inMath. Ann., whose first half was his initial<br />

work on algebras of operators. This was a completely new<br />

branch of ma<strong>the</strong>matics, whose study he continued in a couple<br />

of papers published in 1936 (3), 1937 (1), 1940 (1), and in 1943<br />

(2) (<strong>the</strong>se include his classic four-part series of works with F. J.<br />

Murray). Most likely <strong>von</strong> <strong>Neumann</strong> had no external motivation,<br />

for instance from physics, at least he does not say so in his<br />

first paper. He, partially with Murray, obtained his celebrated<br />

classification, leaving <strong>the</strong> classification of type III algebras<br />

open (this is what Alain Connes completed later). The creation<br />

of <strong>the</strong> <strong>the</strong>ory of <strong>von</strong> <strong>Neumann</strong> algebras shows that his unrivalled<br />

knowledge, speed of thinking, and intuition led him to<br />

a brilliant discovery, whose real value only became evident<br />

three decades after its invention. One important idea was that<br />

<strong>the</strong> dimension of an algebra (or of a space) is strongly related<br />

to <strong>the</strong> invariance group acting on <strong>the</strong> object. The <strong>the</strong>ory of <strong>von</strong><br />

<strong>Neumann</strong> algebras started to flourish around <strong>the</strong> 1960s with<br />

many deep results, and, in particular, with <strong>the</strong> Tomita-Takesaki<br />

<strong>the</strong>ory also revealing profound links of <strong>von</strong> <strong>Neumann</strong><br />

algebras to physics. Not much later <strong>the</strong>ir relation to field <strong>the</strong>ories<br />

was also discovered. Subsequently, this <strong>the</strong>ory became<br />

deeper, and absolutely new connections and applicability<br />

were also discovered. In fact, at least four Fields Medals have<br />

been awarded for radically new results on or in connection<br />

with <strong>von</strong> <strong>Neumann</strong> algebras: to A. Connes in 1982, to V. F. R.<br />

Jones and to E. Witten in 1990, and to M. Kontsevich in 1998. It<br />

is intriguing that Jones’s discovery of <strong>the</strong> famous Jones polynomials,<br />

a topological concept related to knots/braids, was<br />

motivated by ideas from <strong>von</strong> <strong>Neumann</strong> algebras. The easier<br />

and more natural topological construction was afterward<br />

guessed by Witten and rigorously executed by Kontsevich.<br />

See [AI] for lectures of <strong>the</strong> first three medalists and by H. Araki,<br />

J. S. Birman, and L. Fadeev for <strong>the</strong>ir laudations. See also<br />

http://math.berkeley.edu/*vfr/.<br />

Despite <strong>the</strong> fact that <strong>the</strong> revolutionary progress of <strong>the</strong><br />

<strong>the</strong>ory of <strong>von</strong> <strong>Neumann</strong> algebras only occurred in <strong>the</strong><br />

1960s, <strong>von</strong> <strong>Neumann</strong> was conscious of <strong>the</strong>ir potential<br />

importance. In 1954, answering a questionnaire of <strong>the</strong><br />

National Academy of Sciences, he selected as his most<br />

important scientific contributions 1) his work on ma<strong>the</strong>matical<br />

foundations of quantum <strong>the</strong>ory, 2) his <strong>the</strong>ory of<br />

operator algebras, and 3) his work in ergodic <strong>the</strong>ory.<br />

‘‘Side’’ Interests, Ergodic Theory, and Game Theory<br />

Among O<strong>the</strong>rs<br />

Ergodic Theory. The appearance of ergodic <strong>the</strong>ory in <strong>the</strong><br />

aforementioned list is somewhat surprising. To be sure, <strong>von</strong><br />

<strong>Neumann</strong> was well aware of <strong>the</strong> importance of <strong>the</strong> ergodic<br />

<strong>the</strong>orem for <strong>the</strong> foundations of statistical mechanics. (The<br />

ergodic hypo<strong>the</strong>sis grew from ideas of Maxwell, Boltzmann,<br />

Kelvin, Poincaré, Ehrenfest, etc.) As a matter of fact, <strong>von</strong><br />

<strong>Neumann</strong> found and proved <strong>the</strong> first-ever ergodic <strong>the</strong>orem:<br />

<strong>the</strong> L2 version in 1931 (which only appeared in 1932)<br />

[vN32a]. Then George Birkhoff established <strong>the</strong> individual<br />

ergodic <strong>the</strong>orem in 1932. Yet despite his numerous papers<br />

on ergodic <strong>the</strong>ory (in 1927 (1), 1932 (3), 1941 (1), 1942 (1),<br />

and 1945 (1)), it seems to me that it was not one of his most<br />

persistent interests. Fur<strong>the</strong>rmore, he may have felt it as less<br />

than a triumph. When he heard about Birkhoff’s result<br />

‘‘<strong>John</strong>ny expressed pleasure ra<strong>the</strong>r than resentment,<br />

although he did kick himself for not spotting <strong>the</strong> next steps<br />

from his calculations that Birkhoff saw.’’<br />

Progress in applying <strong>the</strong> notion of ergodicity to statistical<br />

mechanics, that is, showing that interesting mechanical systems<br />

are ergodic, has been ra<strong>the</strong>r slow. Only in 1970 could<br />

Sinai [S] find <strong>the</strong> first true mechanical system, that of two hard<br />

discs on <strong>the</strong> 2-torus, whose ergodicity he could prove; he<br />

conjectured that <strong>the</strong> situation is similar for any number of<br />

balls in arbitrary dimension. In 1999 Simányi and I showed<br />

that typical hard-ball systems of N balls of masses m1; ...; mN<br />

and radii r moving on <strong>the</strong> m-torus are hyperbolic; in 2006<br />

Simányi established ergodicity in general under an additional<br />

hypo<strong>the</strong>sis: <strong>the</strong> Chernov-Sinai Ansatz.<br />

O<strong>the</strong>r Interests. Von <strong>Neumann</strong>’s intelligence, culture,<br />

speed, motivation, and communication abilities were at<br />

play in many fields from <strong>the</strong> very start. He touched upon<br />

algebra, <strong>the</strong>ory of functions of real variables, measure <strong>the</strong>ory,<br />

topology, continuous groups, lattice <strong>the</strong>ory, continuous<br />

geometry, almost periodic functions, representation of<br />

groups, quantum logic, etc. I suspect in a sense <strong>the</strong>se were<br />

done ‘‘with his left hand.’’ Never<strong>the</strong>less, for his two-part<br />

memoir ([vN34] and [BvN35]) on almost periodic functions<br />

and groups, he received <strong>the</strong> prestigious Bôcher Prize in 1938.<br />

He would have liked to construct invariant measures for<br />

groups, a goal actually completed by A. Haar in 1932. Von<br />

<strong>Neumann</strong> returned several times to this question, and <strong>the</strong><br />

idea of <strong>the</strong> construction was also exploited in <strong>the</strong> construction<br />

of <strong>the</strong> dimension in his <strong>the</strong>ory of operator algebras.<br />

Game Theory and Ma<strong>the</strong>matical Economics. Two related<br />

left-hand topics deserve special mention: game <strong>the</strong>ory<br />

and ma<strong>the</strong>matical economics. It is well known that <strong>von</strong><br />

<strong>Neumann</strong>’s two game-<strong>the</strong>ory papers in 1928 (<strong>the</strong> more<br />

detailed one is [vN28]) contained <strong>the</strong> formulation and <strong>the</strong><br />

proof of <strong>the</strong> minimax <strong>the</strong>orem (a model of symmetric, twoperson<br />

games had already been suggested by Émile Borel<br />

in 1921, but he had doubts about <strong>the</strong> validity of a minimax<br />

<strong>the</strong>orem). Also, in 1937 <strong>von</strong> <strong>Neumann</strong> published a model<br />

of general economic equilibrium [vN37], known today by<br />

his name. These two sources were basic for his big joint<br />

enterprise with O. Morgenstern, <strong>the</strong> fundamental monograph<br />

[vNM44] Theory of Games and Economic Behavior.<br />

These topics were also <strong>the</strong> objects of his papers in 1950 (1),<br />

1953 (3), 1954 (1), and 1956 (1) (and two fur<strong>the</strong>r unfinished<br />

manuscripts that appeared in 1963). Judging from <strong>the</strong> fact<br />

that in 1994 three Nobel laureates in economics were<br />

named for achievements in game <strong>the</strong>ory (J. Harsányi, J.<br />

Nash, and Reinhart Selten), it is not too bold to surmise that<br />

had <strong>Neumann</strong> lived until this Nobel Prize was founded in<br />

1969, he would have been <strong>the</strong> first to receive it.<br />

Ó 2011 Springer Science+Business Media, LLC


Von <strong>Neumann</strong>’s Mean Ergodic Theorem<br />

Domokos Szász<br />

Ludwig Boltzmann’s ergodic hypo<strong>the</strong>sis, formulated in<br />

<strong>the</strong> 1870s, says: for large systems of interacting particles<br />

in equilibrium, time averages of observables are equal to<br />

<strong>the</strong>ir ensemble averages (i.e., averages w.r.t. <strong>the</strong> timeinvariant<br />

measure) (cf. D. Szász, Boltzmann’s Ergodic<br />

Hypo<strong>the</strong>sis, a Conjecture for Centuries? Hard Ball Systems<br />

and <strong>the</strong> Lorentz Gas, Springer Encyclopaedia of<br />

Ma<strong>the</strong>matical Sciences, vol. 101, 2000, pp. 421-446.). For<br />

Hamiltonian systems <strong>the</strong> natural invariant measure is <strong>the</strong><br />

Liouvillian one. In 1931, Koopman (B. O. Koopman,<br />

Hamiltonian systems and transformations in Hilbert<br />

space, Proc. Nat. Acad. Sci. vol. 17 (1931) pp. 315-318.)<br />

made a fundamental observation: If T is a transformation<br />

of a measurable space X keeping <strong>the</strong> measure l invariant,<br />

<strong>the</strong>n <strong>the</strong> operator U defined by (Uf)(x) := f(Tx) is<br />

unitary on L2. This functional-analytic translation of <strong>the</strong><br />

ergodic problem led <strong>von</strong> <strong>Neumann</strong> in <strong>the</strong> same year to<br />

finding his famous<br />

MEAN ERGODIC THEOREM<br />

T HEOREM 1 (<strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Proof of <strong>the</strong> quasiergodic<br />

hypo<strong>the</strong>sis, Proc. Nat. Acad. Sci. vol. 18 (1932)<br />

pp. 70-82.)<br />

For f 2 L2ðlÞ <strong>the</strong> L2-limit 1<br />

lim<br />

n!1 n f þ f ðTxÞþ þf ðT n 1 xÞ ¼ FðxÞ ð1Þ<br />

exists. The T-invariant function F equals <strong>the</strong> L2-projec tion of <strong>the</strong> function f to <strong>the</strong> subspace of T-invariant<br />

functions, and moreover, R Fdl ¼ R fdl.<br />

Note that for ergodic systems, that is, for those where<br />

all invariant functions are constant almost everywhere,<br />

<strong>the</strong> last claim of <strong>the</strong> <strong>the</strong>orem is just <strong>the</strong> equality of<br />

(asymptotic) time and space averages.<br />

Shortly after <strong>von</strong> <strong>Neumann</strong> discussed this result with<br />

G. D. Birkhoff, <strong>the</strong> latter established his individual<br />

ergodic <strong>the</strong>orem (G. D. Birkhoff, Proof of <strong>the</strong> ergodic<br />

<strong>the</strong>orem, Proc. Nat. Acad. Sci. vol. 17 (1931) pp. 656-<br />

660.) stating that in (1) <strong>the</strong> convergence also holds<br />

almost everywhere. (For a more detailed history of <strong>the</strong><br />

first ergodic <strong>the</strong>orems see G. D. Birkhoff and B. O.<br />

Koopman, Recent contributions to <strong>the</strong> ergodic <strong>the</strong>ory,<br />

Proc. Nat. Acad. Sci. vol. 18 (1932) pp. 279-282.) Von<br />

<strong>Neumann</strong> was also aware of <strong>the</strong> L2 form of his <strong>the</strong>orem:<br />

if U is any unitary operator in a Hilbert space H, <strong>the</strong>n <strong>the</strong><br />

averages 1<br />

n f þ Uf þ þU n 1 ð f Þ converge for every<br />

f 2 H.<br />

Moving to <strong>the</strong> US<br />

Moving to <strong>the</strong> US in 1930–1931 apparently did not make a<br />

big change in <strong>von</strong> <strong>Neumann</strong>’s ma<strong>the</strong>matics. For a time he<br />

did not face challenges such as encountering <strong>the</strong> revolution<br />

of quantum physics in Göttingen. It is known that he had<br />

THE MATHEMATICAL INTELLIGENCER<br />

Von <strong>Neumann</strong>’s Minimax Theorem<br />

András Simonovits<br />

Von <strong>Neumann</strong> made a number of outstanding contributions<br />

to game <strong>the</strong>ory, most notably <strong>the</strong> minimax <strong>the</strong>orem of game<br />

<strong>the</strong>ory, a linear input-output model of an expanding economy,<br />

and <strong>the</strong> introduction of <strong>the</strong> <strong>von</strong> <strong>Neumann</strong>-<br />

Morgenstern utility function. Here I present <strong>the</strong> first of <strong>the</strong>se.<br />

There are two players, 1 and 2, each has a finite number<br />

of pure strategies: s1; ...; sm and t1; ...; tn. If player 1<br />

chooses strategy si and player 2 strategy tj, <strong>the</strong>n <strong>the</strong> first<br />

one gets payoff uij and <strong>the</strong> second one -uij. To hide <strong>the</strong>ir<br />

true intentions, each randomizes his behavior by choosing<br />

strategies si and tj independently with probabilities pi and qj, respectively. For random strategies p = (pi) and<br />

q = (qj), <strong>the</strong> payoffs are <strong>the</strong> expected values u(p,<br />

q) = P i=1<br />

m Pn j=1 piqjuij and -u(p, q), respectively. An<br />

equilibrium pair is defined as (p, q) such that<br />

minq maxp u(p, q) = maxp minq u(p, q).<br />

T HEOREM 1 (<strong>von</strong> <strong>Neumann</strong> 1928) For any twoplayer,<br />

zero-sum matrix game, <strong>the</strong>re exists at least one<br />

equilibrium pair of strategies.<br />

R EMARKS<br />

1. Although ano<strong>the</strong>r ma<strong>the</strong>matical genius, Émile Borel,<br />

studied such games before <strong>von</strong> <strong>Neumann</strong>, he was<br />

uncertain if <strong>the</strong> minimax <strong>the</strong>orem holds or not.<br />

2. This <strong>the</strong>orem was generalized by Nash (1951) (Nobel<br />

Prize in Economics, 1994) for any finite number of<br />

players with arbitrary payoff matrices (J. Nash, ‘‘Non-<br />

Cooperative Games,’’ Annals of Ma<strong>the</strong>matics 54,<br />

(1951) pp. 289–295.).<br />

E XAMPLE. Let us consider <strong>the</strong> following game. Players<br />

1 and 2 play Head (H) or Tail (T) in <strong>the</strong> following<br />

way. Each puts a coin (say a silver dollar) on a table<br />

simultaneously and independently. If <strong>the</strong> result is ei<strong>the</strong>r<br />

HH or TT, <strong>the</strong>n 1 receives <strong>the</strong> coin of 2, o<strong>the</strong>rwise 2<br />

receives <strong>the</strong> coin of 1. There is a single equilibrium:<br />

p i* = 1/2 = q j*, which can be achieved by simply<br />

throwing fair coins.<br />

http://www.econ.core.hu/english/inst/simonov.html<br />

trouble getting used to <strong>the</strong> higher publication-centeredness<br />

of <strong>the</strong> American ma<strong>the</strong>matical community, and <strong>the</strong> lower<br />

level of informal communication as compared with his<br />

European experiences. The famous parties of <strong>the</strong> <strong>von</strong><br />

<strong>Neumann</strong> family in Princeton, offering beyond alcoholic<br />

drinks both ma<strong>the</strong>matical and intellectual communication,<br />

partly solved this problem.<br />

Events of his private life may have influenced his work.<br />

In <strong>the</strong> years around his divorce and second marriage, his<br />

productivity was less than his average (in 1938 he published<br />

just one work, and in 1939 none), but this is not<br />

essential. The proximity and <strong>the</strong>n <strong>the</strong> beginning of <strong>the</strong> war,


<strong>John</strong>ny during his years in <strong>the</strong> United States. (Photo by Alan<br />

Richards, Fuld Hall in Institute for Advanced Study, Princeton)<br />

however, brought a dramatic change in <strong>von</strong> <strong>Neumann</strong>’s<br />

ma<strong>the</strong>matical interests and perhaps in his style. His hatred<br />

for Nazi Germany and his engagement in promoting victory<br />

over it had certainly pushed him toward essentially new<br />

questions. These were connected to new fields and new<br />

problems whose solution he hoped would contribute to <strong>the</strong><br />

big goal. At <strong>the</strong> same time, <strong>the</strong>se problems offered new<br />

ma<strong>the</strong>matical challenges.<br />

War Effort: Ballistics and Shocks<br />

Ballistics. From <strong>the</strong> technological point of view, <strong>the</strong> war<br />

after <strong>the</strong> First World War was its continuation; <strong>the</strong> important<br />

work on improving firing tables of shells did not cease.<br />

(During <strong>the</strong> Second World War Kolmogorov also participated<br />

in similar work; see B. Booss-Bavnbek and<br />

J. Høyrup: ‘‘Ma<strong>the</strong>matics and War: an Invitation to Revisit,’’<br />

Math. Intelligencer 25 (2003), no. 3, 12-25). Oswald Veblen,<br />

who became <strong>the</strong> first professor of <strong>the</strong> Princeton Institute for<br />

Advanced Study in 1932, and was responsible for inviting<br />

<strong>von</strong> <strong>Neumann</strong> to Princeton and later to <strong>the</strong> Institute, had<br />

been <strong>the</strong> commanding officer of this research between<br />

1917 and 1919 in <strong>the</strong> US Army Ordnance Office at Aberdeen<br />

Proving Grounds, Maryland. (Among o<strong>the</strong>rs, <strong>the</strong> great<br />

ma<strong>the</strong>maticians J. W. Alexander and H. C. M. Morse also<br />

worked <strong>the</strong>re under his guidance.) In 1937, <strong>von</strong> <strong>Neumann</strong>,<br />

who from his knowledge of history and from experience<br />

had already expected a war in Europe, decided to join <strong>the</strong><br />

work in Aberdeen. Details of his progressive involvement<br />

are again very nicely described in Macrae’s book, and I<br />

restrain myself from repetitions. The essential thing is<br />

that—because of <strong>the</strong> decreasing density of air with altitude—<strong>the</strong><br />

equations governing <strong>the</strong> trajectories are<br />

nonlinear and cannot be solved exactly and even have new<br />

types of solutions. Later, especially during his 1943 visit to<br />

England, <strong>von</strong> <strong>Neumann</strong> also became interested in <strong>the</strong><br />

dynamics of magnetic mines. His first publications about<br />

shock waves were i) an informal progress report to <strong>the</strong><br />

National Defense Committee, which dates back to 1941,<br />

and ii) its detailed version [vN43]. As usual in <strong>von</strong> <strong>Neumann</strong>’s<br />

ma<strong>the</strong>matics, this very first work already gave a<br />

deep and broad overview, proved interesting new results,<br />

and provided a program, too. This report was <strong>the</strong>n followed<br />

by an analogous report on detonation waves in<br />

1942, and by fur<strong>the</strong>r works in 1943 (3), 1945 (2), 1947 (1),<br />

1948 (1), 1950 (1), 1951 (1), and 1955 (1). (A concise and<br />

nice description of <strong>von</strong> <strong>Neumann</strong>’s approach and results is<br />

given by Fritz in [BV].)<br />

Meteorology and Hydrodynamics. One of <strong>von</strong> <strong>Neumann</strong>’s<br />

favorite subjects was meteorology. He was quite optimistic<br />

that with progress in understanding <strong>the</strong> nature of aero- and<br />

hydrodynamic equations and of <strong>the</strong>ir solutions, and with<br />

<strong>the</strong> development of computation, a practically satisfactory<br />

wea<strong>the</strong>r forecast would become possible. His hopes were<br />

only partially realized. He was certainly aware of <strong>the</strong> chaotic<br />

nature of <strong>the</strong> solutions of hydrodynamic equations, but he<br />

probably did not see sufficiently clearly <strong>the</strong> limitations caused<br />

by chaos (one should not forget that E. Lorentz’s revolutionary<br />

work [Lor] appeared only in 1963, and its import was<br />

not appreciated for quite a while after that).<br />

The study of trajectories of shells, his study of <strong>the</strong><br />

dynamics of magnetic mines in Britain in 1943, <strong>the</strong> work on<br />

hydrodynamics equations, and later his participation from<br />

1943 in <strong>the</strong> Manhattan project, all of <strong>the</strong>se projects brought<br />

home to him <strong>the</strong> fundamental importance of computations,<br />

and consequently that of <strong>the</strong> development of computers.<br />

His Memorandum written in March 1945 to O. Veblen on<br />

<strong>the</strong> use of variational methods in hydrodynamics [vN45b]<br />

starts with <strong>the</strong> sentence ‘‘Numerical calculations play a very<br />

great role in hydrodynamics.’’<br />

Computers: <strong>Neumann</strong>-Architecture and Scientific<br />

Computing<br />

If <strong>the</strong> applied problems mentioned required a tremendous<br />

amount of computations, this appeared most spectacularly<br />

in Los Alamos, where for <strong>the</strong> work on <strong>the</strong> atomic bomb it<br />

was absolutely essential to replace experiments by ma<strong>the</strong>matical<br />

modeling requiring a lot of computations. It is well<br />

known that in August 1944, on <strong>the</strong> railroad platform of<br />

Aberdeen, <strong>von</strong> <strong>Neumann</strong> by chance met Herman Goldstine,<br />

a main figure working in Philadelphia on <strong>the</strong><br />

development of ENIAC. He immediately received a first<br />

lesson on <strong>the</strong> actual level of progress, soon got into <strong>the</strong><br />

work, and presented groundbreaking new ideas (his first<br />

fundamental works were [vN45a] and [BGvN46]). So he not<br />

only became a devoted advocate of <strong>the</strong> project, but substantially<br />

participated in it in various ways; his two most<br />

important contributions were, first, <strong>the</strong> elaboration of <strong>the</strong><br />

principles of <strong>the</strong> programmable computer, of <strong>the</strong> so-called<br />

<strong>von</strong> <strong>Neumann</strong>-computers, and second, <strong>the</strong> implementation<br />

of <strong>the</strong>se principles in <strong>the</strong> construction of <strong>the</strong> computer IAS<br />

to be built at <strong>the</strong> Princeton Institute. This whole story is<br />

described in Aspray [A] and Legendi-Szentiványi [LSz], for<br />

instance. Let me just mention some key words about <strong>von</strong><br />

<strong>Neumann</strong>’s main implementations: RAM, parallel computations,<br />

flow-diagrams, program libraries, subroutines. I<br />

would say that if problems of hydrodynamics and of <strong>the</strong><br />

construction of computers were a necessity and were in <strong>the</strong><br />

air, so to speak, <strong>the</strong> importance of <strong>the</strong> use of computers for<br />

scientific research was not equally obvious. Von <strong>Neumann</strong><br />

Ó 2011 Springer Science+Business Media, LLC


On Reliable Computation<br />

Peter Gács<br />

Von <strong>Neumann</strong>’s best-known contribution to computer<br />

science is <strong>the</strong> conceptual design of general-purpose computers.<br />

Ideas of a stored-program computer had already<br />

been circulating at <strong>the</strong> time among engineers, but <strong>von</strong><br />

<strong>Neumann</strong>’s familiarity with <strong>the</strong> concept of a universal<br />

Turing machine helped <strong>the</strong> clean formulations in <strong>John</strong> <strong>von</strong><br />

<strong>Neumann</strong>’s ‘‘First draft of a report on <strong>the</strong> EDVAC’’ (Technical<br />

report, University of Pennsylvania Moore School of<br />

Engineering, Philadelphia, 1945). Control unit, arithmetic<br />

unit, and memory (which also holds <strong>the</strong> program) still form<br />

<strong>the</strong> major organizational division of most computers. The<br />

arithmetic and control units are modelled well as logic<br />

circuits with connections such as ‘‘and’’, ‘‘or’’, ‘‘not’’, and bit<br />

memory (<strong>von</strong> <strong>Neumann</strong> called <strong>the</strong>se ‘‘artificial neurons’’<br />

after McCulloch and Pitts).<br />

The report mentions <strong>the</strong> problem of physical errors,<br />

without proposing any solution. Von <strong>Neumann</strong> returned to<br />

<strong>the</strong> error correction problem in ‘‘Probabilistic logics and <strong>the</strong><br />

syn<strong>the</strong>sis of reliable organisms from unreliable components’’<br />

(in C. Shannon and McCarthy (eds.), Automata<br />

Studies. Princeton University Press, Princeton, NJ, 1956).<br />

The most important <strong>the</strong>orem of this paper rich in ideas can<br />

be formulated as follows. Call a logic component ideal if it<br />

functions perfectly, and real if it malfunctions with probability,<br />

say, 10 -6 . Suppose that a given logic circuit C is built<br />

with N ideal components. Then one can build out of O(N<br />

log N) real components ano<strong>the</strong>r logic circuit C 0 that computes,<br />

from every input, <strong>the</strong> same output as C, with<br />

probability C 0.99.<br />

In <strong>the</strong> solution, some parts (<strong>the</strong> so-called ‘‘restoring<br />

organs’’) of <strong>the</strong> circuit C 0 are built using a random permutation.<br />

This method was ra<strong>the</strong>r new at <strong>the</strong> time, though<br />

Erd}os’s random graphs and Shannon’s random codes<br />

existed already. The proof of <strong>the</strong> main <strong>the</strong>orem is somewhat<br />

sketchy: a rigorous proof appeared almost 20 years<br />

later (by Dobrushin and Ortyukov, using somewhat different<br />

constructions).<br />

There have been some more advances since (for example,<br />

making <strong>the</strong> circuits completely constructive with <strong>the</strong><br />

help of ‘‘expanders’’), but <strong>the</strong> log N redundancy has not<br />

been improved in <strong>the</strong> general case. For a recent publication<br />

containing references see Andrei Romashchenko, ‘‘Reliable<br />

computation based on locally decodable codes’’ (in<br />

Proc. of STACS, LNCS 3884, (2006) pp. 537–548).<br />

Error-correcting computation, in <strong>the</strong> general setting<br />

introduced by <strong>von</strong> <strong>Neumann</strong>, has not seen significant<br />

industrial applications. Surprisingly, <strong>the</strong> decrease in <strong>the</strong><br />

size of basic computing components (now transistors on a<br />

chip) has been accompanied with an increase in <strong>the</strong>ir<br />

reliability: <strong>the</strong> error rate now is one in maybe 10 20 executions.<br />

This trend has physical limits, however. (Von<br />

<strong>Neumann</strong> himself contemplated <strong>the</strong>se limits in a lecture in<br />

1949. He was not <strong>the</strong> first one, Szilárd probably preceded<br />

him, and <strong>the</strong> nature of <strong>the</strong>se limits has been a subject of<br />

THE MATHEMATICAL INTELLIGENCER<br />

lively discussion among physicists ever since.) Restricting<br />

attention to logic circuits sidesteps <strong>the</strong> problem of errors<br />

in <strong>the</strong> memory and <strong>the</strong> issue of <strong>the</strong> bottleneck between<br />

memory and control unit. There are parallel computing<br />

models without division between memory and computation:<br />

<strong>the</strong> simplest of <strong>the</strong>se, cellular automata, was first<br />

proposed (for o<strong>the</strong>r purposes) by <strong>von</strong> <strong>Neumann</strong> and also<br />

by Ulam. By now, universal reliable cellular automata<br />

have also been constructed.<br />

http://www.cs.bu.edu/*gacs<br />

saw this very quickly, his brain was completely prepared<br />

for it, and he devoted a substantial amount of energy to it.<br />

Reading his papers on this <strong>the</strong>me, one feels that he was<br />

not only aware of <strong>the</strong> great perspectives that computers had<br />

opened up, he was at <strong>the</strong> same time discovering and<br />

enjoying <strong>the</strong> new horizons with a lively, childish curiosity. A<br />

simple ‘‘game’’ was, for instance, to calculate <strong>the</strong> first 2000<br />

decimal digits of e and of p by <strong>the</strong> ENIAC in 1950. Aspray<br />

discusses <strong>von</strong> <strong>Neumann</strong>’s accomplishments in scientific<br />

computing in detail. For <strong>the</strong> record I add that about <strong>the</strong><br />

principles of construction of computers he had reports in<br />

1945 (1), 1946 (1), 1947 (1), 1948 (1), 1951 (2), 1954 (2), and<br />

1963 (1). On scientific computing he had <strong>the</strong> first paper,<br />

joint with V. Bargmann and D. Montgomery [BMvN46], in<br />

1946 (1), on solving large systems of linear equations by<br />

computers. It was followed by works in 1947 (4), 1950 (3),<br />

1951 (2), 1953 (1), 1954 (1), and 1963 (2). He made computer<br />

experiments in number <strong>the</strong>ory, ergodic <strong>the</strong>ory, and<br />

stellar astronomy. He also had several suggestions for random-number<br />

generators (via <strong>the</strong> middle-square method or<br />

<strong>the</strong> logistic map), and, with Ulam, he was also working on<br />

inventing <strong>the</strong> Monte-Carlo method. (I emphasize that <strong>the</strong><br />

publication counts are only for providing a feeling. The<br />

topic of a work is sometimes ambiguous; some manuscripts<br />

only appeared after his death; and some reports may have<br />

appeared as articles (I have not checked overlap).) Had he<br />

lived longer, he certainly would have greeted <strong>the</strong> amalgamation<br />

of computation with science and would have<br />

Commemoration of <strong>the</strong> creation of <strong>the</strong> EDVAC computer. (Credit:<br />

http://www.computer-stamps.com/country/22/Hungary/)


een one of <strong>the</strong> leaders. This is certainly true for computerassisted<br />

proofs. He would have been glad to see <strong>the</strong> birth of<br />

computational sciences: computer science, computational<br />

physics, chemistry, etc. He perhaps would not have been so<br />

glad to see that often computations replace creative and<br />

logical thinking, but this is only a guess.<br />

Last, but not least, I want to turn to a very intriguing<br />

interest of <strong>von</strong> <strong>Neumann</strong>. Having analyzed <strong>the</strong> functioning<br />

of computers, he formulated several related questions. He<br />

initiated research on cellular automata and probabilistic<br />

automata (i.e., automata with unreliable components). He<br />

raised <strong>the</strong> question of constructing self-correcting automata.<br />

Moreover, he envisioned <strong>the</strong> need to compare <strong>the</strong><br />

functioning of computers with that of our brains. His articles<br />

on <strong>the</strong> subject appeared in 1958 in <strong>the</strong> collection<br />

[vN58], and <strong>the</strong> analysis of his thoughts on <strong>the</strong> topic would<br />

deserve a separate discussion.<br />

Epilogue<br />

All in all, fate, often combined with his own decisions, put<br />

before <strong>John</strong> <strong>von</strong> <strong>Neumann</strong> <strong>the</strong> most extraordinary and diverse<br />

scientific challenges. In all cases, he did his job in an ingenious<br />

and superb way. Factors such as his genes, family, education,<br />

<strong>the</strong> intellectual ferment that surrounded him in Budapest, and<br />

<strong>the</strong> intellectual level of his teachers and of Hungarian ma<strong>the</strong>matics<br />

of <strong>the</strong> time, gave him an excellent launch. Besides his<br />

intelligence, knowledge, deductive power, and fantastic mental<br />

speed, he showed depth, perspective, and taste; his diverse<br />

scientific and human interests, complemented by his education<br />

in chemical engineering, contributed to his unrivalled courage,<br />

openness, and flexibility. By excelling in an unusually broad<br />

spectrum of ma<strong>the</strong>matical activities, he became an outstanding<br />

representative of twentieth-century ma<strong>the</strong>matics, whose influence<br />

was unbelievably wide within and outside ma<strong>the</strong>matics.<br />

Von <strong>Neumann</strong>’s achievements demonstrate convincingly <strong>the</strong><br />

strength of <strong>the</strong> ma<strong>the</strong>matical approach, ‘‘unreasonable effectiveness<br />

of ma<strong>the</strong>matics,’’ as Wigner put it. It is not<br />

overstatement to compare <strong>the</strong> achievements of <strong>John</strong> <strong>von</strong><br />

<strong>Neumann</strong> to those of Archimedes, Newton, Euler, or Gauss.<br />

Von <strong>Neumann</strong> was exceptionally widely known among<br />

ma<strong>the</strong>maticians, and <strong>the</strong>re are plenty of anecdotes related to<br />

him. I think that as a student, I heard from my professor A.<br />

Rényi <strong>the</strong> saying: ‘‘O<strong>the</strong>r ma<strong>the</strong>maticians prove what <strong>the</strong>y can,<br />

<strong>Neumann</strong> what he wants.’’ (It fits, though I have mentioned<br />

that he was not happy that it was not himself who found<br />

Gödel’s incompleteness <strong>the</strong>orem or Haar’s construction of <strong>the</strong><br />

invariant measure of a locally compact group or Birkhoff’s<br />

proof of <strong>the</strong> individual ergodic <strong>the</strong>orem.)<br />

Not long ago, Dan Stroock from MIT mentioned to me <strong>the</strong><br />

following at least half-serious opinion: ‘‘A genius ei<strong>the</strong>r does<br />

things better than o<strong>the</strong>r people, or does <strong>the</strong>m completely<br />

differently (orthogonally) from o<strong>the</strong>r people.’’ I think it is<br />

true about <strong>von</strong> <strong>Neumann</strong> that he did most things better than<br />

o<strong>the</strong>r ma<strong>the</strong>maticians would have done. An example of<br />

an ‘‘orthogonal’’ scholar could well be Einstein. Never<strong>the</strong>less,<br />

I think of times when <strong>von</strong> <strong>Neumann</strong> also did things<br />

orthogonally.<br />

Let me finish by citing a well-known anecdote. Question<br />

to Wigner: ‘‘How is it that Hungary produced so many<br />

geniuses in <strong>the</strong> early 20th century?’’ Wigner’s answer: ‘‘That<br />

many geniuses? I don’t understand <strong>the</strong> question. There was<br />

only one genius: <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>.’’<br />

Brief Biography<br />

1903, December 28: Born in Budapest<br />

1914-1921: Lu<strong>the</strong>ran Gymnasium, Budapest (Teacher of<br />

maths: László Rátz. Tutored by Gábor Szego; afterward by<br />

M. Fekete and L. Fejér.)<br />

1921 Winter term - 1923 Summer term: Berlin University,<br />

student in chemistry, attends lectures in physics and<br />

ma<strong>the</strong>matics (Professor of Ma<strong>the</strong>matics: Erhard Schmidt,<br />

Professor of Chemistry: Nobel Laureate Fritz Haber).<br />

1923 Summer term - 1926 Summer term: ETH, Zürich, student<br />

in chemical engineering, attends lectures in physics<br />

and ma<strong>the</strong>matics, too (Hermann Weyl, György Pólya);<br />

October 1926: Diploma in chemical engineering.<br />

1921 Winter term - 1925 Summer term: registered student of<br />

ma<strong>the</strong>matics at Budapest University; March 1926: Ph.D. in<br />

ma<strong>the</strong>matics (Supervisor: L. Fejér?).<br />

1926 Fall term - 1927 Summer term: visiting Göttingen<br />

University, grant from Rockefeller Foundation (D. Hilbert,<br />

L. Nordheim, R. Courant, K. Friedrichs, P. Jordan, future<br />

Nobel Laureate physicists Max Born, J. Franck, W. Pauli,<br />

W. Heisenberg).<br />

1927 Fall - 1929: Privatdozent at Berlin University.<br />

1929: Privatdozent at Hamburg University.<br />

1930 - 1938: Marriage with Marietta Kövesi.<br />

1930: Visiting Lecturer at Princeton University.<br />

1931 - 1933: Visiting Professor at Princeton University.<br />

1933 - 1957: Professor, Member of <strong>the</strong> Institute for<br />

Advanced Study, Princeton.<br />

1935: Daughter Marina <strong>von</strong> <strong>Neumann</strong> born.<br />

1938: Marriage with Klári Dán.<br />

1957, February 8: Dies in Walter Reed Hospital, Washington,<br />

buried in Princeton Cemetery<br />

A complete bibliography of <strong>John</strong> <strong>von</strong> <strong>Neumann</strong> can be<br />

found on <strong>the</strong> Internet: http://www.info.omikk.bme.hu/<br />

tudomany/neumann/javnbibl.htm. Most papers, and manuscripts<br />

are in [T], and some in [BV].<br />

ACKNOWLEDGMENTS<br />

I express my sincere gratitude to István Hargittai and Peter<br />

Lax for <strong>the</strong>ir most valuable remarks and to P. Gács and<br />

András Simonovits for <strong>the</strong>ir inserts. Special thanks are due<br />

to Réka Szász for polishing my English and to J. Fritz, I.<br />

Juhász, D. Petz, L. Rónyai, A. Simonovits, and A. Szenes for<br />

stimulating discussions.<br />

REFERENCES<br />

[A] W. Aspray, <strong>John</strong> <strong>von</strong> <strong>Neumann</strong> and <strong>the</strong> Origins of Modern<br />

Computing. MIT Press, Cambridge, MA, 1990.<br />

[AI] Sir M. Atiyah, D. Iagolnitzer (eds.), Fields Medallists’ Lectures.<br />

World Scientific, Singapore, 1997.<br />

[BV] F. Bródy, T. Vámos (eds.), The <strong>Neumann</strong> Compendium. World<br />

Scientific, Singapore, 1995.<br />

Ó 2011 Springer Science+Business Media, LLC


[Lax] P. Lax, Remembering <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>. Proc. of Symposia<br />

in Pure Ma<strong>the</strong>matics, 50:5-7, 1990.<br />

[LSz] T. Legendi, T. Szentiványi, Leben und Werk <strong>von</strong> <strong>John</strong> <strong>von</strong><br />

<strong>Neumann</strong>. Mannheim, 1983.<br />

[Lor] E. N. Lorentz, Deterministic Nonperiodic Flow. J. Atmos. Sci.,<br />

20:130-141, 1963.<br />

[Luk] J. Lukacs, Budapest 1900: A Historical Portrait of a City & Its<br />

Culture. Grove Press, 1988.<br />

[M] N. Macrae, <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>. The Scientific Genius. Pan<strong>the</strong>on<br />

Books, New York, 1992.<br />

[S] Ya. G. Sinai, Dynamical Systems with Elastic Reflections.<br />

Russian Math. Surveys, 25:139-189, 1970.<br />

[T] A. H. Taub, <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>: Collected Works I-VI.<br />

Pergamon Press, Oxford, 1961-1963.<br />

WORKS BY VON NEUMANN:<br />

[vN23] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Zur Einführung der transfiniten Zahlen.<br />

Acta Sci. Math. Szeged, 1:199-208, 1923.<br />

[HNvN27] D. Hilbert, L. Nordheim, J. <strong>von</strong> <strong>Neumann</strong>, Über die Grundlagen<br />

der Quantenmechanik. Math. Ann. 98:1-30, 1927.<br />

[vN28] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>. Zur Theorie der Gesellschaftsspiele.<br />

Math. Ann. 100:295-320, 1928.<br />

[vN29] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Zur Algebra der Funktionaloperatoren<br />

und Theorie der normalen Operatoren. Math. Ann. 102:<br />

370-427, 1929.<br />

[vN32a] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Proof of <strong>the</strong> Quasi-Ergodic Hypo<strong>the</strong>sis.<br />

Proc. Nat. Acad. Sci., 18:70-82, 1932.<br />

[vN32b] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Ma<strong>the</strong>matische Grundlagen der<br />

Quantenmechanik. Springer, Berlin, 1932.<br />

THE MATHEMATICAL INTELLIGENCER<br />

[vN34] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Almost Periodic Functions on a<br />

Group. Trans. Amer. Math. Soc. 36:445-492, 1934.<br />

[BvN35] S. Bochner, <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Almost Periodic Functions<br />

on Groups, II. Trans. Amer. Math. Soc. 37:21-50,<br />

1935.<br />

[vN37] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Über ein ökonomisches Gleichungssystem<br />

und eine Verallgemeinerung des Browerschen<br />

Fixpunktsatzes. Erg. eines Math. Coll, Vienna, ed. by K.<br />

Menger 8:73-83, 1937.<br />

[vN42] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Theory of Detonation Waves. Progress<br />

Report, 1942.<br />

[vN43] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Theory of Shock Waves, Progress<br />

Report, 1943.<br />

[vNM44] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, O. Morgenstern, Theory of Games and<br />

Economic Behaviour. Princeton University Press, 1944.<br />

[vN45a] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, First Draft of a Report on EDVAC, pp.<br />

48, 1945.<br />

[vN45b] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Use of Variational Methods in Hydrodynamics.<br />

Memorandum to O. Veblen, March 26, 1945.<br />

[BGvN46] A. W. Burks, H. H. Goldstine, <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>,<br />

Preliminary Discussion of <strong>the</strong> Logical Design of an Electronic<br />

Computing Instrument, Part I, 1946.<br />

[BMvN46] V. Bargman, D. Montgomery, <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, Solution<br />

of Linear Systems of High Order. Report, 1946.<br />

[vN47] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, The Ma<strong>the</strong>matician, in The Works of <strong>the</strong><br />

Mind, R. B. Heywood (ed.) University of Chicago Press, 180-<br />

196, 1947.<br />

[vN58] <strong>John</strong> <strong>von</strong> <strong>Neumann</strong>, The Computer and <strong>the</strong> Brain (Silliman<br />

Lectures). Yale University Press, pp. 88, 1958.

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