Talks

The study of entanglement in the ground states of locally interacting many-body quantum systems has provided connections between spectral properties and the computational resources required for tensor-network calculations. Generic quantum states have volume-law entanglement, but ground states are typically observed to satisfy an area law, with corrections in gapless systems. I will introduce a new framework that provides rigorous upper bounds on entanglement entropies of states with fixed energy. These results constrain (i) ground-state entanglement in both gapped and gapless systems in general spatial dimensions, (ii) the crossover from area-law to volume-law entanglement as the system energy is increased and (iii) the computational resources necessary for calculations of zero-temperature response functions.

The Dark Energy Spectroscopic Instrument (DESI) is the largest galaxy redshift survey to date, aiming to catalog ~63 million galaxies over 17000 deg^2 of the sky by the end of 8 years of observation. The DR1 analyses were completed in 2024 with exciting new constraints on cosmological parameters within the standard LCDM model as well as extensions such as evolving dark energy. I will discuss the cosmological results from the DR1 fullshape and BAO analysis which was presented in the Fall of 2024 and the theory systematic tests/validation that went into it. I will then discuss the advantages of including cross correlations of DESI galaxies with CMB lensing and some key results from my joint analysis of 3D clustering with CMB lensing using the DESI DR1 galaxy sample and ACT DR6 and Planck PR4 lensing maps. In particular we find that just including galaxy-lensing cross-correlations on top of the fullshape and BAO analysis tightens amplitude constraints by ~30%. The second data release (DR2) spans three years of observation with analyses expected to be presented in Spring of 2026. I will briefly discuss the expected improvements in constraining power from DR2 and summarize the types of analyses that DESI will perform and their cosmological relevance.

The connected wedge theorem states that in order to have a scattering process in the bulk, it is necessary to have O(1/G_N) mutual information between certain “decision” regions in the boundary theory. While this large mutual information is not generally sufficient to imply scattering, previous literature showed that for a certain class of geometries, bulk scattering is implied by a certain relation between two (possibly non-minimal) Ryu–Takayanagi surfaces. In this work, we show that the 2-to-2 version of the theorem becomes an equivalence in pure AdS3: large mutual information between appropriate boundary subregions is both necessary and sufficient for bulk scattering. This result allows us to extend previous findings to a broader class of asymptotically AdS3 spacetimes, which we illustrate with the spinning conical defect geometry. In contrast, we find that matter sources can disrupt this converse relation, and that the n-to-n version of the theorem with n>2 lacks a converse even in the AdS3 vacuum.

Topologically ordered phases of matter have long been regarded as lying beyond the Landau–Ginzburg paradigm of symmetry breaking. Our recent studies of anyon condensation, however, suggest that such phases may, in fact, be brought back within the Landau–Ginzburg framework. In this talk, I will present a framework that brings topological phases back into the Landau–Ginzburg picture by reformulating the string-net model to be a genuine lattice gauge theory coupled to anyonic matter fields. Within this modified model, topological phase transitions induced by anyon condensation and their consequent phenomena, such as order parameter fields, coherent states, Goldstone modes, and gapping gauge degrees of freedom, can be formulated as Landau's effective theory of the Higgs mechanism.