## Mathematician Emma Lehmer dies at 100

### by Robert Sanders

**Mathematician Emma Trotskaya Lehmer, for many years a vital member of the University of California, Berkeley, mathematics community, where her late husband and father-in-law both taught as members of the faculty, died on Monday, May 7, at the age of 100.**

She passed away peacefully in her sleep at her home in Berkeley.

She passed away peacefully in her sleep at her home in Berkeley.

Lehmer was an accomplished mathematician who specialized in number theory, publishing 56 papers during her lifetime, 21 of them with her husband, Derrick Henry "Dick" Lehmer, a UC Berkeley professor of mathematics who died in 1991. The couple founded in 1969 the annual West Coast Number Theory Meeting, "one of their most enduring contributions to the world of mathematicians," wrote John D. Brillhart, a professor emeritus of mathematics at the University of Arizona in Tucson who was a former student of Lehmer's husband.

"In the 63 years during which they collaborated, the Lehmers were a research team who personally influenced a large number of people with their knowledge, their courtesy and sociability, and their fine mathematical work," Brillhart said.

The University of California's anti-nepotism policy forbade Emma Lehmer from teaching at UC Berkeley while her husband was on the faculty, though she taught a few statistics courses when the policy was briefly suspended during World War II. She took this in stride, however, claiming that it allowed her to concentrate more on research. She pursued mathematics while raising two children, publishing her last paper in 1993, when she was 87

"Mathematics was always going on in our household," said her daughter, Laura Lehmer Gould. "She was not a neglectful mother, but I don't think we stood in her way very much."

During the war, Lehmer's husband, a leading authority on number theory and computation, helped develop and test the first modern digital computer, called the ENIAC (Electronic Numerical Integrator and Calculator), at the Aberdeen Proving Ground in Maryland. Though the ENIAC was designed to calculate ballistic trajectories, Emma and her husband were able to use it occasionally on weekends to do calculations impossible with paper and pencil, such as factoring numbers to find large primes - numbers divisible only by themselves and one. Dick Lehmer and his father, UC Berkeley mathematics professor Derrick Norman Lehmer, had earlier built an electro-mechanical sieve capable of factoring very large numbers - a machine that they displayed at the Chicago World's Fair in 1933.

As related in the book, "Notable Women in Mathematics" (1998), Lehmer recalled that she and her husband would arrange child care, stay at the lab all night long while the ENIAC processed one of their problems, then return home at dawn.

Lehmer was born Emma Trotskaya in Samara, Russia, on Nov. 6, 1906, and moved with her family in 1910 to Harbin, Manchuria, where her father represented a Russian sugar company. Schooled at home until the age of 14, when a local school finally opened, she was inspired to pursue engineering and mathematics by an exceptional high school teacher and planned on continuing her education in Russia.

These plans were thwarted by the upheavals of World War I and the communist revolution. According to Lehmer's daughter, Lehmer began to chafe at the insular Jewish community in Harbin and longed "to come to the United States and become an engineer." She earned money to pay her way by translating, babysitting and tutoring children in mathematics and music.

Lehmer was admitted to UC Berkeley in 1924 to study engineering, but developed a greater interest in mathematics that led her to work during her sophomore year on number theory with Derrick Norman Lehmer. In his lab, she first met his son, Dick, who was then a junior. Upon her graduation with a B.S. in mathematics in 1928, they wed.

Emma Lehmer moved with her husband to Brown University, where she obtained an M.S. in mathematics in 1930, the same year her husband earned his Ph.D. Dick Lehmer taught at various universities until his father retired from UC Berkeley in 1937, opening the door for his own hiring. Dick Lehmer was appointed to the UC Berkeley mathematics faculty in 1940 and the couple, now with two children, moved to Berkeley.

Emma Lehmer frequently collaborated with her husband and her father-in-law. The three developed methods for computer computations to assist in solving number theory problems, and in 1930 they applied to the Carnegie Institution for funds to construct a machine that would, according to their proposal, check "a million numbers in about three minutes" in order to find factors of large whole numbers.

She never regretted her lack of a Ph.D., writing in the article "On the advantages of not having a Ph.D.," that, "First of all there are lower expectations. If one happens to discover something new, one's peers are pleasantly surprised and generous in their praise. This is good for the morale ...."

Except for a brief period in the early 1950s, when the Lehmers protested UC's loyalty oath by moving to Los Angeles, where Dick Lehmer became director of the National Bureau of Standards' Institute for Numerical Analysis at UCLA, the couple remained at UC Berkeley until Dick Lehmer retired in 1972.

Emma Lehmer was guest of honor at a three-day conference of mathematical talks held at UC Berkeley in 2000 to honor a century of the three Lehmers' mathematical contributions. Brillhart published an announcement of Emma Lehrer's 100th birthday in the December 2006 issue of the journal Notices of the

*American Mathematical Society*, suggesting that her friends send cards, and this unleashed a flurry of birthday cards that, among them, included 275 signatures.

Lehmer was an accomplished pianist in her younger years, and her daughter recalled that the family often played together, with the father playing cello, daughter playing violin or viola, and son playing clarinet. Lehmer and her husband also played informally with several faculty music groups.

An atheist and a political liberal, Lehmer campaigned for Adlai Stevenson in the 1950s, spent a lot of time registering voters at sidewalk tables and even walked picket lines in Berkeley to protests UC's involvement in Lawrence Livermore National Laboratory's bomb-making research. She also loved gardening, small children, animals and hiking in the Sierra Nevada.

Lehmer is survived by her daughter, Laura Lehmer Gould, of Woodside, Calif.; son, Donald, of Berkeley; four grandchildren; five great-grandchildren; and one great-great-granddaughter, almost all of whom live in the Bay Area.

In her will, Lehmer set aside money to establish a graduate fellowship in number theory at UC Berkeley. At her request, there will be no memorial service.

11 May 2007