Date February 1, 2019
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Unpacking Mathematics

ICERM is advancing basic research and the next generation of top scientists.

There was no tightly packed pile of cannonballs at Brown’s Institute for Computational and Experimental Research in Mathematics (ICERM) during its semester-long program on “Point Configurations” in 2018. But the famous mathematical question behind such an arrangement was fully present.

Over the course of the spring, more than 300 people in mathematics, physics, and computer science from around the world shared ideas at one of the country’s eight mathematical institutes funded by the National Science Foundation. The goals? Stimulating further fundamental research and advancing knowledge.

Looming in the background during deliberations was one of the most enduring problems in mathematics—Kepler’s Conjecture, informed by the esteemed 17th-century mathematician and astronomer Johannes Kepler’s question: What is the densest way to stack equal-sized cannon- balls? The solution to the problem about efficient sphere packing in three-dimensional space may be easy to visualize—an arrangement of fruit at a supermarket is a commonly cited representation—but the theory has proven to be one of mathematics’ most difficult to solve rigorously and precisely over the centuries.

The ICERM program included sphere packing along with a variety of related topics. “Point configurations have a lot of real-world applications,” said ICERM director and Brown mathematics professor Brendan Hassett. Among the areas related to its study are optimization work such as coding and information theory, modeling the Earth’s atmosphere, dense packing of platelets in biology, digital communications, and studying crystallization through which a solid forms.

“ICERM’s goal is to develop basic research that can be disseminated widely,” Hassett said. Launched in 2010, the research institute is like a think tank with a cast that deliberately keeps rotating. It brings together some of the world’s best mathematical minds to explore topics in pure and applied math, computer science, and related disciplines.

Fundamental research in the mathematical sciences produces unexpected benefits.

– Jill Pipher

In the Point Configurations program, participants made the ICERM offices their base for more than three months, using spaces designed to encourage and support collaborations. From formal presentations to workshops, from spontaneously planned ad hoc programs to conversations over lunch, participants discussed current research questions and started new collaborations.

“One major impact of the program has been to strengthen the internal coherence of this widespread subject of growing importance, which intersects with geometry, analysis, physics, and computer science,” said Peter Grabner of Graz University of Technology in Austria, a member of the program’s organizing committee.

“New collaborations were formed that have already led to progress on such topics as lattice theory, packing, and statistical physics,” said the chair of the organizing committee, Edward Saff, a mathematics professor at Vanderbilt University. Communication among workshop participants is continuing, and a follow-up conference in two years is being considered, as is a new academic journal on the subject.

Leading scholars from around the world attended the program—a few months later, one of the workshop leaders, Akshay Venkatesh of the Institute of Advanced Study in Princeton, was awarded a Fields Medal, an award often described as the Nobel Prize of Mathematics.

A large goal of ICERM programs is to develop the next generation of top researchers. “The camaraderie among participants played an important role in the program’s success,” Saff said. “There were no lines of division between graduate students, postdoctoral students, and senior scientists.”

Enhancing the program was intense activity in the mathematical field about its subject in the months leading up to its start. Henry Cohn, a principal researcher for Microsoft Research New England who is also on the Scientific Advisory Board of ICERM, published widely noted research on sphere packing in 24 dimensions. His work was discussed both at ICERM and in a Distinguished Lecture series with him, hosted by the mathematics department at Brown and attended by faculty, undergraduates, and graduate students. The problem of two-dimensional sphere packing was solved in the mid-20th century by Lazlo Fejes Tóth, but it was not solved in three dimensions until Thomas Callister Hales did so in 1998, an accomplishment confirmed by computer check in 2014.

“Fundamental research in the mathematical sciences produces unexpected benefits,” said Jill Pipher, Brown’s vice president for research, and also founding director of ICERM and professor of mathematics. “The research that is pursued, simply because it pushes the frontiers of mathematical truth further, often pays dividends years and decades later in solving real-world problems,” she added.

For instance, she said, number theory, once thought to have no connection to the broader world, eventually led to a new paradigm in encryption and helped make the Internet age imaginable and digital financial transactions possible.

Though by design ICERM programs, which are supported by a five-year, $17.5M federal grant, involve far more visitors than Brown faculty and students, the impact on Brown is large. Dan Abramovich, a professor of mathematics and chair of mathematics, said, “An ICERM program floods Brown with a group of researchers in a particular topic. Our departments and other centers benefit from a supply of seminar and colloquium speakers, concentrated exposure to current research in a particular topic, and a general expansion of the Brown community, often keeping links well after the end of a program.”