# Ballot Problems, Viruses, and the Challenge of Being First

When Mathematics Professor Allon Percus’s brother, Orin, was born in 1969, the City University of New York, where their mother Ora Engelberg Percus taught math, was among many institutions that 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.

So when she was pregnant with Allon in the spring of 1971, she decided not to tell CUNY administrators.

“She was very thin, and big tent dresses were popular, so even in the third trimester no one suspected anything,” Percus said. “They found out she had a second baby when 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.”

If that isn’t enough to illustrate his mother’s character and tenacity, he offered another observation.

“She was never one to suffer fools gladly,” he said, “particularly fools in positions of authority.”

The Engelberg Fellowships will expand opportunities to excellent students who otherwise might not be able to attend, particularly those from underrepresented and nontraditional groups in the mathematical sciences.” — Allon Percus

CGU has received a $2 million gift to establish the Engelberg Fellowships in the Mathematical Sciences. The endowment, which honors the memory of Ora Engelberg Percus, will provide significant financial support to students who are members of the university’s Institute of Mathematical Sciences (IMS). The gift was announced in October.

“The Engelberg Fellowships will expand opportunities to excellent students who otherwise might not be able to attend, particularly those from underrepresented and nontraditional groups in the mathematical sciences,” Percus said, adding that he hopes recipients display the same intellectual rigor, and firm resolve that helped his mother achieve success at a time when universities operated with stifling rules that are not only antiquated today, but in some cases illegal.

## From Tel Aviv to Manhattan

Ora Engelberg came of age in the Middle East, in a society that in some ways was less socially conservative than that of the United States. She was born in what was then the British Mandate of Palestine, the daughter of pioneers who had arrived from Eastern Europe in the 1920s. She grew up in Tel Aviv, studied mathematics at the Hebrew University of Jerusalem, and served three years in the Israeli army, reaching officer rank.

After earning her master’s degree in mathematics, she accepted a PhD fellowship offer from Columbia University and moved to the Upper West Side of Manhattan in 1960, where she lived until her death 60 years later.

Her husband, Jerome Percus, was a physics professor whose research interests often intersected with hers, and he became her closest scientific collaborator. “Each had deep, deep respect for the other—well-merited respect. They were always talking math to each other,” Allon Percus said.

## An Eye to the Future

Two of Ora Engelberg Percus’s research interests proved prescient many years later.

In 1964, the *Journal of Applied Probability* published her paper on the likelihood that a candidate could start out well ahead when the ballots are counted and end up falling behind, as was the case in the 2020 presidential election. The basic takeaway from her elegant analysis of probabilities is that it can happen easily.

“I think she may have been the first one to apply that set of mathematical methods to this ‘ballot problem,’” Percus said. “In mathematics, as in many other things, it is sometimes better to be the second person who discovers something. When you’re first, no one really knows what to do with your work. I think one of the challenges my mom faced was that she was often the first.”

She also was interested in the spread of viruses.

“In collaboration with my dad, she embarked on a long and fruitful research program in mathematical immunology, developing probabilistic models to describe and predict the coevolution of viruses and immune response,” Percus said. “It was only days after her death that the COVID-19 pandemic arrived in full force, putting modeling efforts of this kind in the highest demand.”

## Real-World Applications

Ora Engelberg Percus’s desire to find answers to real-world challenges is evident in the students who attend the IMS. They often work in joint teams with faculty members and industry clients through the institute’s math clinics. Many have spent years in the professional world before reentering academia, and they bring with them a wealth of experience, often outside traditional mathematics boundaries. The same is true for several of the institute’s professors.

Allon Percus believes that the Engelberg Fellowships will attract even more highly talented students, including those who might have considered CGU but went elsewhere because of financial considerations. He also hopes that the gift serves as a catalyst for others to invest in the institute, which an external review team lauded last April as being a superb outlier in mathematics graduate education.

Though he is honored to shine a spotlight on the IMS with the Engelberg Fellowships gift, he is quick to note that he was simply a conduit and not a philanthropist. The funds came from his mother’s estate and reflected her investment acumen: She purchased Apple stock in 1983.

“She often reminded me that I had suggested that she sell it 20 years ago,” Percus said. “I have no idea why she decided to keep it when the share price of Apple was in the basement. But I guess that if you have enough experience studying ballot problems and seeing how likely it is that candidates who are behind during most of the count can pull ahead later on, you learn to take large dips in the stock market with a grain of salt.”

- Learn more about the Institute of Mathematical Sciences
- Learn more about the Engelberg Fellowships in the Mathematical Sciences.