Department Colloquia

The Physics Department Colloquia are held at 11:30 am Tuesdays in Gzang 123

Spring 2024

From Molecules to Moduli : data driven model development for active materials

January 16, 2024

Aparna Baskaran, Brandeis

Abstract In this talk I will do three things : i) give a philosophical overview of active matter research, ii) present a pedagogical discussion active nematohydrodynamics and iii) briefly show some ongoing research efforts to use data driven approaches to leverage theory for prediction and design of active flows. 

Exploring the Structure and Dynamics of Matter in High-Energy Collider Experiments

January 30, 2024

Bernd Surrow, Temple University

Abstract: Understanding the properties of nuclear matter and its emergence through the underlying
partonic structure and dynamics of quarks and gluons requires a new experimental facility
in hadronic physics known as the Electron-Ion Collider (EIC). A US-based facility capable of
colliding high-energy polarized electron and ion beams at high luminosity has been envisaged
for a long time and articulated as the highest priority for new construction. The EIC will
address some of the most profound questions concerning the emergence of nuclear properties by
precisely imaging gluons and quarks inside protons and nuclei, such as the distribution of gluons
and quarks in space and momentum, their role in building the nucleon spin and the properties
of gluons in nuclei at high energies. The EIC facility will be realized at Brookhaven National
Laboratory, profiting from the existing Relativistic Heavy-Ion Collider (RHIC) facility, allowing
to collide both polarized proton beams and heavy ion beams for more than two decades.
High energy polarized p+p collisions at √ s = 200−500 GeV at RHIC provide a unique way
to probe the proton spin structure and dynamics using well-established scattering processes. The
production of jets and hadrons is the prime focus of gluon polarization studies. The production
of W−(+) bosons at √ s = 500 GeV provides an ideal tool to study the spin-flavor structure of
the proton.

After a summary of final results concerning the spin structure and dynamics of quarks and
gluons obtained by the STAR experiment at RHIC, the status and perspectives of a US-based
ElC facility will be presented in this colloquium, including highlights of the planned physics
program, the current detector design of a new EIC experiment, and anticipated next steps.

Patterns, defects, and transport on active membranes

February 27, 2024

Sumantra Sarkar, IISc Bangalore

Abstract: The plasma membrane of a cell gives the cell its shape, protects it from intruders, and acts as a communication hub. The diversity of the membrane's functions reflects the diversity of patterns and structures found on the membrane. Therefore, understanding the origin and the dynamics of membrane patterns has been of recent interest. Specifically, we have come to appreciate biological activity's key role in creating and maintaining these patterns. In this talk, I shall provide an overview of the field and describe some of the ongoing projects in my group on active pattern formation. Specifically, I'll show (a) how arrested coarsening of topological defects on active surfaces can help us understand the formation of signaling platforms on the cell membrane and (b) how the same defects can make molecular transport robust against thermal fluctuations.

The Evolution of Antibody Responses upon Repeated Vaccination

March 12, 2024

Arup Chakraborty, MIT

Abstract: Infectious disease-causing pathogens have plagued humanity since antiquity, and the COVID-19 pandemic has been a vivid reminder of this perpetual existential threat. Vaccination has saved millions of lives, and effective vaccines have helped control the COVID-19 pandemic. However, we do not have effective vaccines against rapidly mutating viruses, such as HIV; nor do we have a universal vaccine against seasonal variants of influenza or new variants of SARS-CoV-2. I will describe how by bringing together approaches from statistical physics, virology and immunology, progress is being made to address this challenge. I will focus on the antibody arm of this challenge. Antibodies are produced by a far from equilibrium stochastic dynamic evolutionary process. I will describe statistical physics-based models of antibody evolution and complementary data from animals and humans that shed light on how this process might be modulated to produce desired antibody responses.

Exoplanet atmospheres in the era of JWST and Ariel

March 26, 2024

Quentin Changeat, STScl

Abstract: The James Webb Space Telescope (JWST), launched in 2022, has already revolutionized the field of exoplanetary atmospheres by providing a much higher sensitivity and access to new wavelength ranges compared to previous observatories. For instance, the first studies of exo-atmospheres using JWST data have unveiled previously unseen molecular species in exoplanet atmosphere, provided precise measurements of atmospheric thermal structures, and shed light on cloud and haze properties for the first time. Simultaneously, the European Space Agency (ESA) is preparing Ariel, a dedicated facility that will study the atmospheres of approximately 1000 exoplanets. This mission will enable the first detailed population studies of exo-atmospheres to understand the nature and formation of these worlds.

Such a revolution in our observing capabilities creates both opportunities and challenges for the field of exoplanet atmospheres. In this seminar, I will present recent observational campaigns and simulation efforts highlighting the pivotal role of JWST and Ariel for our field, and comparing with past generation observatories such as the Hubble Space Telescope. The presentation will focus on the description of modern interpretation techniques and outline the role of exoplanet atmospheres in addressing fundamental questions of planetary science.

Geometric Approach to Quantum Fields

April 9, 2024

Eisenbud Seminar: Jonathan Heckman, University of Pennsylvania

Abstract: Quantum field theory (QFT) is the universal language used by physicists to describe a wide variety of phenomena in Nature. Quite remarkably, this framework has also found many applications within pure mathematics. But what is quantum field theory and how is it characterized? In this talk, I highlight recent progress made in understanding QFT using the geometry of extra dimensions predicted by string theory. This includes the discovery of entirely new kinds of QFTs in a wide range of spacetime dimensions, leading to a remarkable interplay between physics and geometry. 

Lunch reception at 12:30 in Abelson 333