The wandering mathematician

«If numbers aren’t beautiful, I don’t know what is.»

It is not enough to be in the right place at the right time. You should also have an open mind at the right time.»

«Some French socialist said that private property was theft … I say that private property is a nuisance.»

– Paul Erdös (1913-1996)

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The mathematician Paul Erdös used a special vocabulary consistently in his speech:

• People who stopped doing mathematics had “died”
• Children were Epsilons (in calculus, an arbitrarily small positive quantity is commonly denoted by the Greek letter $\epsilon$)
• Wives were Bosses
• Husbands were Slaves
• Married Men have been Captured and were Liberated when divorced
• Alcoholic Drinks were Poison
• God was The Supreme Fascist or SF
• Church crosses were Plus signs
• Music was Noise
• Countries which he classified as imperialist were given a name that began with a small letter (e.g. israel)
• the U.S. was samland
• the Soviet Union was joedom (after Joseph Stalin)
• F.B.I and O.G.P.U (which later became the K.G.B) were combined as f.b.u.

Erdös had never applied for citizenship anywhere he lived, and had acquired Hungarian citizenship only by accident of birth. He belonged to no political party, but had a fierce belief in the freedom of individuals as long as they did no harm to anyone else.

Because he seemed to be in a state of Brownian motion, it was often hard to locate him at any given time. For many years the way to contact him was to call Ron Graham of Bell Labs on the east coast, Paul Bateman of the University of Illinois, or Ernst Strauss at UCLA to know of Erdös’ whereabouts.

In 1954, Erdös wanted to go the International Congress of Mathematicians (held every four years), which was to be in Amsterdam that August. As a non-citizen leaving the U.S. with plans to return, he had to apply for a re-entry permit. After being interviewed by an INS agent in South Bend in early 1954, he received a letter saying that re-entry would be denied if he left the U.S. He hired a lawyer and appealed only to be turned down again. No reason was ever given, but his lawyer was permitted to examine a portion of Erdös’ file and found recorded the following facts:

• He corresponded with a Chinese number theorist named Hua who had left his position at the University of Illinois to return to (red) China in 1949. (A typical Erdös letter would have begun: Dear Hua, Let p be an odd prime …)
• He had blundered onto a radar installation on Long island in 1942 while discussing mathematics with two other non-citizens.
• His mother worked for the Hungarian Academy of Sciences, and had had to join the communist party to hold her position.

To Erdös, being denied the right to travel was like being denied the right to breathe, so he went to Amsterdam anyway. He was confident that he could easily obtain a Dutch and an English visa. The Dutch gave him a visa good for only a few months, and England would not let him come, likely because if they chose to deport him, the only country obligated to accept him was communist Hungary. By then, Erdös was a member of the Hungarian Academy of Sciences, but he would go to Hungary only if his friends could assure him that he would be permitted to leave. At this point, he swallowed his pride and obtained a passport from israel (note the punctuation) which served to give him freedom to travel anywhere in western Europe.

He was permitted to return to the United States in the summer of 1959 on a temporary visa to attend a month long conference on number theory in Boulder, Colorado.

For many years, he traveled only with a small leather briefcase containing a change of socks and underwear in addition to a wash-and-wear shirt, together with some paper and a few reprints.

About a year later, the United States government lost its fear of Erdös and gave him resident alien status once more. He never had trouble going in or out of the U.S. again.

Erdös had lived from hand to mouth most of the time until the late 1950s. When the Russians sent Sputnik into orbit and the space race began, there was a vast increase in government support of research. This made it possible for his many friends and co-authors to give him research stipends. This had little effect on his lifestyle. His suitcase was rarely more than half full, and he gave away most of his money to help talented young mathematicians or to offer cash prizes for solving research problems of varying degrees of difficulty.

For his epitaph he suggested: “I’ve finally stopped getting dumber” (Hungarian: “Végre nem butulok tovább”).