November 5, 2021

Getting to Know Ora Engelberg: Researcher, Immigrant, Mother

PARTNERS IN LIFE & SCHOLARSHIP: Ora Engelberg Percus and husband Jerome Percus during a visit to China. Of their collaborations, son Allon says, "Each had deep, deep respect for the other—well-merited respect. They were always talking math to each other."

Claremont Graduate University has received a $2 million gift to endow the Engelberg Fellowships in the Mathematical Sciences, in honor of the late mathematician Ora Engelberg Percus.

From their parents’ New York apartment, lined with thousands of books and yellowed papers accumulated over 56 years, Allon Percus, a professor in CGU’s Institute of Mathematical Sciences, and Orin Percus, a professor of linguistics with the Université de Nantes in France, talked with science writer Yen Duong about their mother Ora, her life in mathematics, and the fellowships in her memory that will be awarded starting next year.

The Engelberg Fellowships will initially fund one new graduate student every year, offering four years of financial support in CGU’s IMS program.

(Note: this interview has been edited and condensed.)


Yen Duong: Before we start talking about your mom, tell me about the motivation for establishing these fellowships in her name.

Allon Percus: Part of it corresponds to an urgent need. The Engelberg Fellowships will expand opportunities to excellent students who otherwise might not be able to attend, particularly from underrepresented and nontraditional groups in the mathematical sciences.

The other part of it is that our mom has always been a little bit in the shadow of our dad, Jerome Percus, who taught for 62 years at the Courant Institute of Mathematical Sciences and Physics Department at NYU. He was an extraordinary scientist, but in many ways he also had a very privileged life and was always able to work on exactly what he wanted. In his later years, he admitted that he was quite spoiled in that sense. Our mom was not spoiled at all, and had to face many large obstacles. From my perspective, this fellowship in honor of her is an attempt to restore some symmetry there.

Orin Percus: It makes her part of an institution in a way she never was.

AP: Also, her publications all used the name Percus after she was married. Had times been different, she probably would not have used our dad’s last name. The name Engelberg Fellowships is intended to recognize that.

YD: Your mother came to the U.S. in 1960 from Israel, where her parents had been some of the first Jewish pioneers from the 1920s. In Israel, she’d become a lieutenant in the army engineering corps, staying an extra year after the mandatory two years of military service. What was it like for her coming to the U.S.?

AP: It must have been a shock. She had grown up in a society that was just in the process of being structured. I suspect that, for women, it was much easier to be recognized in Israel than it was here. She must have felt a tremendous amount of conservatism when she came here.

YD: After getting her master’s degree from the Hebrew University in 1959 and then lecturing at Tel Aviv University, she started her PhD at Columbia in 1960 and defended in 1964. To me, that’s pretty fast, but you said that she ended up delaying her defense.

AP: There’s a whole story involving immigration difficulties that she had in the United States. She was under threat of deportation. This was in the aftermath of the McCarthy period—she was accused of voting in a Communist Party election.

OP: Not only voting in a Communist Party election, but being a candidate herself! And it turns out that the year of that election was before she was even old enough to vote!

AP: The only way that she could stay in the country was to remain a student. Columbia hired a lawyer to help her. She defended December 15, 1964, which was intentionally past the deadline for a fall degree. That gave her until the spring, and then she and our dad got married on May 20, 1965.

Allon (left) and Orin Percus

YD: After defending, she taught at Columbia University’s Teachers College and then at City College, part of the City University of New York system. That defense delay was just the first time that she went around bureaucracy, which you’ve told me she had ”very little patience” for.

AP: When Orin was born, CUNY and many other institutions required pregnant women to take unpaid maternity leave without benefits. The assumption was that the husband would provide the benefits to cover pregnancy and childbirth.

When I was born, she decided just not to tell them that she was pregnant. She was very thin, and everyone was wearing big tent dresses anyway in the early ’70s. So even in the third trimester, no one suspected anything. They found out she had a second baby because I was born on May 13 and our dad had to proctor the final exam in one of her classes.

They made her take off the following fall semester without pay, but she had already thought to coordinate this with our dad’s sabbatical. So we all spent the next year in London and our parents were visiting faculty at Middlesex Hospital in mathematical biology.

YD: Of course, that’s what I think of when I have two small kids, that I should just move them to another country for a semester and do research! Since your parents were each other’s main collaborators through their mathematical careers, was your house full of math conversations?

OP and AP, laughing: All the time!

OP: We would go to conferences and universities with them; this was very much part of the culture.

AP: The social environment that we grew up in at home was very mathematical. Comments at dinner were often valid for all epsilon greater than zero. Many jokes tended to be mathematically tinged.

YD: Please tell me a joke.

AP: There’s a mathematician sitting outside a house and the house is empty. Someone walks into the house, and then all of a sudden two people walk out. And the mathematician says, “Oh, if one more person goes back into that house, it will be empty again.”

YD: …

AP: Anyway … our mom was working on problems involving interpretations of clinical trials. It’s a very timely topic right now, when you have vaccines with emergency use approval based on what are ostensibly incomplete clinical trial information. The valid interpretation of statistics was always her core interest.

The Engelberg Fellowships, her sons say, will make Ora Engelberg Percus “part of an institution in a way she never was.”

YD: You got back to the U.S., and then she left City College in 1973, when the math department decided to close their graduate program and she was denied tenure. What happened next?

AP: She was determined to keep up her research career. After ’73, she was basically doing mathematics as an independent, unaffiliated researcher. It’s pretty mind-boggling when you think about it. There were some windows of opportunity, because both of us started preschool at a very young age.

OP: She wasn’t really able to work when we were there. She would close the door to the living room …

AP: Closing a door is not always sufficient. I really don’t think it was easy at all. Not surprisingly, there was a bit of a pause in her scientific productivity.

YD: (screaming children in background) Your mother’s story is hopeful to me personally, as she gets more time and starts to adjunct when you are teenagers. What research was she working on then?

AP: She was trying to establish whether various pseudo-random number generator algorithms were valid for particular applications. There are some scary stories about random number generators that were the default methods on mainframe computers at the time. The most famous nightmare story was RANDU, a random number generator that was used for a large number of physical simulations—basically, all of those results were suspect.

It was a class of random number generators called linear congruential generators.

YD: Linear congruential generators … in this case that’s when you multiply your previous output by a big number, then modulo some other integer. That process ensures that your previous output and your current output aren’t too correlated. And you choose the big number and the modulo integer so that you don’t have too much periodicity.

AP: But that’s not good enough. You also care about what happens if you look at correlations between three or four successive supposedly random trials. She was working on that problem in the context of the NYU Ultracomputer, which was a DOE-funded project and one of the first attempts at building a large-scale cluster. That was how she got back into really active research and academia—she became a research faculty member at the Courant Institute and got her own large NSF grant.

TIMELY NOTICE: The opening page of Ora Engelberg’s prescient paper (in light of the 2020 U.S. presidential election) about ballot problems published in 1965.

YD: Wow, so she went from academia, to home with the kids in 1973 doing independent research, then being an adjunct in the 1980s, and then back to academia in 1991. I just want to note that between those two professorships, between 1973 and 1991, she had 22 publications, which included a six-year stint as a senior research scientist at Courant. Then she ended up leaving academia just a few years later and retiring early, in 1995, when she was 61.

AP: Her grant was awarded in 1992, and it was recommended for renewal by the NSF program officer in 1995. But there were some hiccups involving negotiations with the university and disagreements about her benefits. It ended up with her asking the funding agency not to renew the grant, and then she retired.

YD: The benefits: Usually universities will apportion a percentage of researchers’ grants for benefits for the employee. And for adjuncts, that percentage is higher than for tenure track faculty.

AP: Exactly. The issue was that, in addition to her continuing to receive benefits as our dad’s spouse, the university wanted to charge the grant at that much higher benefit rate. She saw this as double-billing and a money grab on the part of the university.

Our mom had a very clear view in her head of what was right and what was wrong. In this case, she drew her line in the sand. … Given how much of her professional experience had been clouded by problems that she felt were not of her making, and difficulties that were imposed upon her in the academic setting, it must have given her a tremendous amount of personal satisfaction to thumb her nose at such a big institution!

YD: But true to form, she stayed active in research even after retiring in 1995. You mentioned an interest in mathematical and statistical paradoxes, like Simpson’s paradox: that error of aggregation where you can get the opposite effect if you put two groups together. 

AP: She and our dad published a paper on Parrondo’s paradox, which is like a dynamic version of Simpson’s paradox: Random selection of playing two asymptotically losing games can result in a winning game.

You start to see a new phase in her research career. She started new collaborations with people at Los Alamos and at the Santa Fe Institute, working on problems in combinatorics. These were also related to what she was doing earlier with the clinical trials and involved screening the performance of a drug. You can perform experiments on well-chosen clusters of individuals that overlap in such a way that you can get meaningful and efficient results.

A SINGULAR LIFE: Ora Engelberg Percus

YD: Do you think the recipients of the Engelberg Fellowships will connect to Ora’s story?

AP: We have a strong program in Claremont thanks, in part, to students who are not “conventional” in the math graduate school sense. I have quite a few students who have come back to school after years in the professional world. That’s a powerful connection with my mom, who went back to a career in academia after an extended pause.

But above all, the goal of these fellowships is to bring in talent that we would otherwise not be able to. The Engelberg Fellowships are a way of honoring Ora’s tenacity, helping our program thrive by rewarding merit no matter where it is found.