2024-2025 Department Colloquia

Fall 2024

Into the First Billion Years with JWST

November 12, 2024

Rohan Naidu, MIT

Abstract: One of the last great unknowns in our history of the universe is when and how the first galaxies emerged after the Big Bang. These galaxies transformed the cosmos – they illuminated the invisible scaffolding of dark matter that underpins the universe, they ionized the intergalactic reservoirs of hydrogen, and they synthesized the elements that would one day seed life on Earth. Thanks to JWST, these enigmatic galaxies are finally coming into view. In this talk I will present latest results on these sources, and preview ongoing experiments I am leading. I will discuss new classes of galaxies being revealed at the highest redshifts such as remarkably luminous early systems, a surprisingly abundant population of obscured black holes (``Little Red Dots"), and extremely metal-poor (perhaps metal-free?) sources. I will describe novel strategies to hone in on the elusive protagonists of cosmic reionization, the last large-scale process that touched almost every baryon in the universe. Throughout, I will outline how in the coming years JWST, Roman, and the upcoming ELTs promise a once-in-a-generation expansion of the astrophysical frontier to the brink of the Big Bang.

Broken Symmetries in Living Matter

October 29, 2024

Nikta Fakhri, MIT

Abstract: Active processes in living systems create a novel class of nonequilibrium matter composed of many interacting components that individually consume energy and collectively generate motion or mechanical stress. In this talk, I will discuss experimental tools and conceptual frameworks we develop to uncover laws governing fluctuations, order, and self-organization in systems in which individual components break time reversal symmetry. I will describe how such frameworks provide powerful insight into dynamics of nonequilibrium living systems across scales, from the emergence of thermodynamic arrow of time to spatiotemporal organization of signaling protein patterns and discovery of odd elasticity.

Broken Symmetry Clues for Fundamental Physics

October 15, 2024

Matthew Reece, Harvard

Abstract: Symmetries provide a powerful organizing principle in physics. However, there are reasons to believe that exact global symmetries do not exist in consistent quantum-gravitational theories. Thus, we expect all symmetries in the world around us to be at least slightly broken. The extent and nature of symmetry breaking phenomena can offer important clues about fundamental physics. In this talk, I will discuss both phenomenological aspects of broken symmetries, including a look at high-precision experiments searching for flavor- and CP-violating effects; and theoretical aspects, including efforts to better understand the constraints quantum gravity imposes on approximate symmetries.

Theoretical Physics in the Ocean

October 1, 2024

Albion Lawrence, Brandeis

Abstract: The ocean is a complex multiscale fluid system which manifests deep problems in nonequilibrium physics. In this colloquium I will discuss two projects aimed at uncovering the nature of ocean dynamics at the mesoscales and submesoscales covering distances from 1-(few x 100) km, and time scales from hours to weeks. These scales dominate the kinetic energy of the ocean, and are crucial for how the ocean transports heat, salt, carbon, and nutrients. I will begin by surveying what is known about the dynamics at these scales, and how they are measured, particularly by satellites. Inspired by the recently-launched Surface Water and Ocean Topography (SWOT) satellite, which gives high-resolution 2-dimensional maps of the topography of the ocean surface, I will describe a technique known as the scattering transform and its power in analyzing fundamental aspects of fluid dynamics and fluid turbulence, in ways that go beyond quantities traditionally used in fluid turbulence. In the last part of the talk I will discuss the dynamics of inertia-gravity waves, wind-driven waves that govern the properties of the upper ocean and which are a significant source of kinetic energy. In many physically relevant situations these waves are governed by a Schrodinger equation, and intuition from quantum mechanics can be profitably used to understand their dynamics.
Future Colliders and Detectors

September 17, 2024

Marc-Andre Pleier, BNL

Abstract: Particle colliders and their experiments have played a crucial role in discovering the fundamental building blocks of our universe and the forces between them. I will give a glimpse into the many ideas for future accelerators that are being discussed before outlining the feasibility study under way for the next major facility at CERN. Its goal is to study the latest discovered particle - the Higgs boson - as well as the overall consistency of the theoretical framework we call the Standard Model of particle physics in more depth to address some of the unsolved mysteries of our universe.

Pattern Formation in Abstract Droplets

September 3, 2024

Bennett Sessa, Brandeis

Abstract: The hydrodynamics of many living systems -- from morphogenesis to mitosis -- involve, in part, a dynamic competition between bulk active stresses and interfacial tension. We mimic this competition experimentally to understand how activity and capillarity compete to generate functionalized structures. A microtubule-driven active liquid is embedded in a binary, polymeric liquid that phase separates, forming active droplets surrounded by a passive background. Fluctuations in active stress near the boundary induce spontaneous curvature changes in the soft interface. The complex coupling between the bulk active fluid and deformable interfaces creates several exciting phenomena. First, we characterize a nonequilibrium analog of the classic Saffman-Taylor instability using both experiment & theory. Second, we describe how nonreciprocal coupling between the active fluid and interface drives asymmetric fluctuations. Our work supports the claim pressure in active systems is generally not a state variable but rather depends on mesoscopic details. We end with an outlook on time-reversal asymmetry in active systems. Altogether our work demonstrates active droplets exhibit rich hydrodynamic and thermodynamic behavior that can help us better understand the fundamental nature of nonequilibrium living systems.