Department Colloquia
The Physics Department Colloquia are held at 11:30 am on Tuesdays in Abelson 131.
Fall 2025
November 11, 2025
Abstract: I will discuss recent developments on a novel kind of global symmetry known as non-invertible symmetry. It is implemented by conserved operators that do not have an inverse, going outside the paradigm set by Wigner's theorem. Nonetheless, they lead to new conservation laws, novel topological phases of quantum matter, and insights into particle phenomenology. I will start with the example in the Ising lattice model, and proceed to discuss applications in pion decay and axion physics.
October 28, 2025
Abstract: Over the past 15 years, significant tensions have been observed in flavour-changing neutral current decays of b-hadrons. Collectively referred to as the flavor anomalies, these effects have attracted considerable attention due to the strong sensitivity of such rare processes to potential new physics. One of the most notable tensions appears in the angular distributions of the rare decay B → K*0 μ+ μ−. This seminar will present the most precise measurements of this decay to date, based on data collected with the LHCb experiment during Runs 1 and 2 of the LHC, and will discuss the implications of these new results for our understanding of the flavor anomalies.
September 30, 2025
Abstract: Until recently most cancer biologists operated with the assumption that the most common route to metastasis and to therapy resistance involves cells of the primary tumor transforming to a motile single-cell phenotype via complete EMT (the epithelial-mesenchymal transition). This change allows them to migrate individually to distant organs, eventually leading to clonal growths in other locations. But, a new more nuanced picture has emerged, based on advanced measurements and on computational systems biology approaches. It has now been realized that cells can readily adopt states with hybrid properties, use these properties to move collectively and adapt to hugely stressful environments. This talk will focus on the accumulating evidence for this revised perspective, the role of biological physics theory in instigating this whole line of investigation, and on open questions currently under investigation.
September 16, 2025
Abstract: Fluid dynamics plays an important role across many natural systems ranging from the Earth’s ocean and atmosphere, to planetary interiors & subsurface oceans and the interiors of stars. In this talk, I will describe the role and interaction of turbulence, waves, and mean flows in these systems, and how they affect predictions of their structure and evolution. I will discuss how turbulently-excited waves have been shown to drive mean flow oscillations in planetary atmospheres, and may also drive similar flows in stars. While these flows have been observed for decades, many aspects of the flows remain a mystery. Studying simplified physical models of these processes has led to insights that apply across atmospheric science, planetary science, and astrophysics. This highlights the importance of studying universal physical processes across these different systems, and how advances in fluid dynamics are crucial to the broader geophysics and astrophysics communities.
September 2, 2025
Valérie Bettaque (Brandeis)
Quantum is Magic
Abstract: Large-scale quantum computing is probably still decades away, but its promising applications are already being studied intensely. Seemingly able to solve certain classes of problems much more efficiently than their classical counterparts, it raises the question how quantum computers are able to achieve this, and if this advantage can be quantified for general quantum systems. In this talk I present one possible such characterization, often referred to as non-stabilizerness or “magic”. I show how this advantage can be measured using the so-called stabilizer Rényi entropy, and how we managed to compute it for the Sachdev-Ye-Kitaev model even at large system sizes. This analysis opens up new ways to understand how the “quantumness” of large chaotic systems affects our ability to simulate them, and maybe even if it has implications for modern theories of quantum gravity.
Emily Duden (Brandeis)
The Road to New Physics with the ATLAS Inner Tracker and Long-lived Particles
Abstract: Long-lived particles are a promising signature to look for new physics. These particles can travel macroscopic distances within a particle detector before decaying, producing displaced signatures invisible to traditional physics analysis. To observe low-probability phenomena through long-lived particles and beyond, both 1) more data and 2) improved data analysis strategies are needed. The first will be accomplished at the LHC with the High Luminosity upgrade, which will increase the number of proton-proton collisions and produce an order of magnitude more data than currently available. High radiation and particle density associated with this luminosity increase will render the current ATLAS detector inoperable, necessitating major detector upgrades. The largest of these upgrades is the replacement of the current tracking detectors with the all-silicon Inner Tracker, or ITk. In this talk, I will describe critical testing of ITk detector components, as well as new analysis techniques used to search for unconventional long-lived particle signatures.