PGSS 2026

PGSS Invited Faculty Lecture: Shedding Light on Dark Matter with Particle Accelerators

Christian Herwig

Assistant Professor, Department of Physics

What is the nature of dark matter (DM)? Thermal relics provide an excellent candidate, predicting DM masses within a few orders of magnitude of the proton, and small couplings to the known Standard Model (SM) particles. Particle accelerators are critical instruments in this search, where machines that achieve the highest energies and intensities are deeply complementary in exploring the full range of allowed masses. I will start by discussing a two-fold strategy that leverages datasets collected by the ATLAS Experiment at the Large Hadron Collider and the Light Dark Matter Experiment at the SLAC LCLS-II, before pivoting to a few recent developments and ideas for the future.

A Simple Quantum System With Universal Black Hole Features

Loki Lin

Department of Physics

Could a cloud of electrons in a magnetic field and a charged black hole ever look the same? Any sane person would say of course not -- one is an ordinary condensed-matter system, while the other is an exotic object in gravity. But under specific circumstances, they can share the same low-energy dynamics. In this talk we will set up the two sides of this correspondence. We will introduce the problem of black hole entropy and the idea of holography, argue that the near-horizon physics of charged black holes reduces to quantum gravity in two dimensions, and write down a simple quantum mechanical model of electrons on a sphere which surprisingly realizes the same spectrum as 2d quantum gravity. This is an example of universality: the fact that very different microscopic systems often end up behaving the same way when the details are blurred out. The talk is based on arXiv:2601.08908 with Anna Biggs and Juan Maldacena. We will assume knowledge of only undergraduate-level quantum mechanics and statistical mechanics.

How Deep Are the Cracks in Cosmology? Insights from DESI

Prakhar Bansal

Department of Physics

For more than two decades, the standard cosmological model, ΛCDM, has provided a remarkably successful description of observations ranging from the cosmic microwave background to the large-scale structure of the Universe. However, the increasing precision of modern surveys has revealed a number of intriguing anomalies, including the Hubble tension, hints of dynamical dark energy, and the cosmological constraints on neutrino masses. Determining whether these discrepancies are statistical fluctuations, unresolved systematics, or evidence for new physics has become one of the central challenges in cosmology. In this talk, I will discuss how recent measurements from the Dark Energy Spectroscopic Instrument (DESI) are helping to address these questions. I will present several complementary analyses that use DESI data to test extensions of ΛCDM and assess the significance of current cosmological tensions. I will also highlight ongoing efforts toward DESI full-shape analyses using joint power-spectrum and bispectrum measurements. Together, these studies provide a broad perspective on the current status of cosmological tensions and the extent to which DESI data support extensions beyond ΛCDM.

Why 3D Is So Frustrating: Understanding Structural Complexity Through Curved-Space Packings

Michelle Thran

Department of Physics

Whether synthetic or natural, nanoparticles in our three-dimensional universe self-assemble into structures with a remarkable degree of complexity. However, it is difficult to predict assemblies for all but the simplest shapes and pair potentials. Part of this challenge lies in the fact that most particle environments which are favored locally are incommensurate with the global geometry, a situation known as "geometric frustration". The purpose of this work is to study the extent to which this emergent complexity can be understood as resolved geometric frustration. Geometric incommensurability can be resolved by curving space; Curved spaces offer new compatible particle arrangements and can therefore “relax” geometric frustration in assemblies. In many cases, features of assembled structures can be interpreted as topologically necessary defects of curved-space assemblies.

Full speaker list coming soon!