Eva Silverstein is 2023 Eisenbud Lectures speaker

Eisenbud poster The Mathematics department is pleased to announce that this year’s speaker for the Eisenbud Lectures in Mathematics and Physics is Eva Silverstein of Stanford University. The lectures will take place at Brandeis University from March 28th – March 30th. The Eisenbud Lectures are the result of a generous donation by Leonard and Ruth-Jean Eisenbud intended for a yearly set of lectures by an eminent physicist or mathematician working close to the interface of the two subjects.

Professor Silverstein is an eminent theoretical physicist who has done creative, pioneering and influential work in string theory, quantum field theory, and both conceptual and observational aspects of cosmology. She was a Sloan Fellow and a MacArthur Fellow; she is currently a Simons investigator; a fellow of the American Physics Society; and a fellow of the American Academy of Arts and Science.

Silverstein is a fascinating speaker, and these lectures promise to be enlightening and entertaining in equal measure. Here’s the lecture schedule (refreshments will be available before each talk):

  • Tuesday, March 28th at 4pm in Abelson 131: “The accelerating universe and rigid Einstein manifolds”.  For Zoom link, please contact Catherine Broderick.
  • Wednesday, March 29th at 11am in Abelson 333: “The accelerating universe and integrable deformations of quantum field theories”
  • Thursday, March 30th at 10am in Abelson 333: “Optimization and sampling from energy-conserving Hamiltonian dynamical systems”

There will be a reception held on campus at Feldberg Lounge in the Hassenfeld Building after the first colloquium on Tuesday, March 28th.  All are invited to attend.

Prof. Albion Lawrence and Prof. Bong Lian are hosting the 2023 lecture series.

Herzfeld paper named “2023 Hot PCCP article”

images from Herzfeld paperIn a new paper (DOI: 10.1039/d2cp05648h), selected as a “2023 Hot PCCP article”, the Herzfeld group has shown that the “Lewis dot” representation of electrons can predict states that have otherwise been predicted only by the most advanced implementations of quantum mechanics.

Basically, the structures and reactions of molecules are controlled by the interactions of electrons with each other and with atomic nuclei. However, the process is complicated by the fact that wave properties are important for particles as light as electrons. The gold standard is to explicitly model these properties using wave mechanics. But it is convenient to have an implicit description that is more accessible and intuitive. These are the “Lewis dots” that are generally used to represent bonds and reaction mechanisms in chemistry courses and journal articles. Lewis dots are semi-classical particles: classical in the sense of being associated with a location in space, but non-classical in that they don’t stick to the oppositely charged nuclei and can have two different spin states.

In recent years, the Herzfeld group has sought to quantify this picture. A subtlety is that the interactions between electrons is spin dependent due to the antisymmetry of electron wave functions. This explains why electrons of unlike spin often form pairs. However, the charges of electrons should always repel one another and Linnett suggested already in 1961 that two electrons should only co-localize if they are both sufficiently attracted to the same inter-nuclear region. In their new paper, the Herzfeld group shows that, a careful representation of the effects of wave function anti-symmetry, leads to Linnett-like structures when there are not enough internuclear basins to induce all the electrons to form simple pairs. A striking example is given by benzene. The traditional semi-classical representation of benzene, as a resonance between two structures with alternating single and double bonds, is obviated by a structure with three electrons in each carbon-carbon bond (shown here with the six carbon kernels in teal, six hydrogen kernels in white, and 15 valence electrons of each spin in pink and magenta).

Publication: Emergence of Linnett’s “double quartets” from a model of “Lewis dots.” Judith Herzfeld. Physical Chemistry Chemical Physics, Issue 7, 2023.

Brandeis students ranked well at the Putnam Math Competition

putnam competition posterThe Brandeis team did very well at the Putnam Mathematics Competition this year. The Brandeis team ranked 39 out of 456 institutions! This is a great result, especially given that small institutions are naturally at a disadvantage in such rankings.

The William Lowell Putnam Mathematical Competition is hosted by the Mathematics Association of American (MAA). It is an annual competition that began in 1938 for undergraduate college students from the US and Canada. The event consists of two 3-hour sessions where students work individually to solve six mathematical problems. It is famous for the intricate mathematical puzzles it proposes, whose solutions require imagination and inventiveness.

Eight Brandeis students participated in the weekly competitions at Brandeis, with Ben Kamen, Issac Berger and Phong Pham going on to compose the Brandeis Team at the national competition. Student Ben Kamen received an honorable mention since he scored 58th out of 3415 participants. The other Brandeis students also did very well.

Congratulations to the Brandeis team and all participants, and a great thank you to the Putnam coaches Kiyoshi Igusa, Professor of Mathematics and PhD student Tudor Popescu!

Albion Lawrence receives 3-year funding from NASA’s Physical Oceanography program

Albion Lawrence

The ocean is a highly complex, multiscale system, with many types of motions occurring simultaneously. Ocean turbulence between 1km and hundreds of kilometers (the *submesoscale* and *mesoscale*) contains about 90% of the kinetic energy of the ocean, and is crucial for understanding the vertical and horizontal transport of heat, salt, carbon, and microorgamisms; and for understanding the coupling between the ocean and atmosphere. At these scales, internal waves driven by tides and wind also propagate through the ocean and play an important role in mixing such quantities. Characterizing and disentangling these different classes dynamics, and understanding how they interact, is a central problem in physical oceanography. This has become particularly salient with the December 2022 launch of the Surface Water and OceanTopography (SWOT) satellite, which will observe the ocean from space with unprecedented resolution.

Typical studies focus on the kinetic energy as a function of physical scale, (the “power spectrum”), to characterize ocean turbulence. However, this is a fairly blunt instrument and requires more precision than is available. Thus, Joern Callies, Assistant Professor for Environmental Science and Engineering at Caltech and Albion Lawrence, Professor of Physics, intend to use high-order statistical tests, inspired by tools used by observational cosmologists, quantum field theorists, and statistical physicists, to study mesoscale and submesoscale ocean dynamics using satellite observations, direct measurements made in the ocean, and numerical modeling. Their proposal, “Higher-order statistics of geostrophic turbulence and internal waves”, for which Professor Lawrence is the PI and Professor Callies is the Co-PI, was just selected for funding by the Physical Oceanography program at NASA. It was one of nine proposals selected out of 40 in 2022.

Professor Lawrence has been a theoretical high energy physicist for over thirty years, and has only recently begun working in climate-related physics problems. He just co-wrote two papers (arxiv.org, arxiv.org) on black holes and quantum gravity. To further help his move into this new field, he was also awarded a Simons Foundation Pivot Fellowship to spend the 2023-24 academic year embedded in Professor Callies’ group at Caltech. Brandeis’ collegial and interdisciplinary environment had a lot to do with the success and fun Professor Lawrence has had to date. This direction of his research was spurred by his involvement in a large multi-department NSF IGERT grant in “Geometry and Dynamics” that ran from 2011-2018; and got a very important boost from a Provost’s Innovation on “Nonequilbrium Statistical Mechanics of the Ocean and Atmosphere” that Lawrence received in 2019.

Brain rhythms coordinate neural networks to mediate memory-guided decision making

Significance of findings: The authors report coordination mechanisms between oscillations recorded in the CA1 subfield of the hippocampus, prefrontal cortex, and olfactory bulb and cell ensemble activity in CA1 and prefrontal cortex during odor-cued decision-making. The important findings support the hypothesis that the β rhythm plays a role in coordinating CA1-prefrontal cortex ensembles during decision-making. Sensory-guided decision-making is of broad significance to many readers who are studying executive functions and decision-making behaviors, and the observations reported in this manuscript provide convincing evidence of mechanisms that may support these functions and behaviors.

“Rhythmic coordination and ensemble dynamics in the hippocampal-prefrontal network during odor-place associative memory and decision making”. Claire A Symanski, John H Bladon, Emi T Kullberg, Paul Miller, Shantanu P Jadhav. eLife 2022, 11:e79545. DOI: 10.7554/eLife.79545

Simons Foundation: Jané Kondev discusses the Mathematics of Biology

As part of their 4 Minutes With series, the Simons Foundation recently presented a video of Jané Kondev, William R. Kenan, Jr. Professor of Physics, discussing the Mathematics of Biology. Kondev is a 2020 Simons Investigator in Theoretical Physics in Life Sciences.

Image: Simons Foundation

Kondev is a theoretical physicist who works primarily on problems in molecular and cell biology (Kondev Group).



Protected by Akismet
Blog with WordPress

Welcome Guest | Login (Brandeis Members Only)