Talks

In this talk, I will describe recent developments in our understanding of edge modes associated to subregions in gauge theories, leveraging their realization as reference frames. I will begin with the picture in classical Maxwell theory, where I will introduce the concept of subregional Goldstone mode as a relational observable parametrizing the corner symmetry group. With this as a guiding principle, I will then move on to non-Abelian lattice gauge theory, where we can carry out the construction directly at the quantum level. I will characterize a novel hierarchy of relational subregional algebras, which encompasses the so-called electric and magnetic center algebras usually considered in the literature, for which we provide a new general definition. This leads to corresponding entropy hierarchies. Interestingly, some of the relational algebras can be factors, and so the physical Hilbert space factorizes. Except in the Abelian case, the subregional Goldstone mode is generically only defined on a subspace of the Hilbert space, stemming from the incompleteness of certain edge mode frames. I will conclude with on-going efforts to have a quantum description of edge modes in the continuum, employing algebraic QFT methods. An overarching theme will be the relation between the subregional Goldstone mode and the asymptotic soft sector of the theory. 

The first and smallest systems of particle dark matter gravitationally condensed directly out of the smooth mass distribution of the early universe. This formation mechanism left these "prompt cusps" with uniquely compact r^-1.5 density profiles and linked their properties tightly with the cosmic initial conditions. Prompt cusps are the densest and most abundant dark matter systems. I will present their basis in simulations and theory, and I will show how they bring new opportunities to test the physics of dark matter and the early universe. For example, the measured kinematics of dwarf galaxies strongly constrain dark matter models that were primordially warm, while gamma rays from galaxy clusters strongly constrain dark matter models with matter-antimatter symmetry. I will also discuss small-scale structure formation for an alternative dark matter candidate – primordial black holes (PBHs) – based on a new simulation that fully resolves the inter-PBH dynamics. For example, gravitational interactions involving PBH binaries can eject PBHs at extreme speeds, making a component of "hot dark matter" that suppresses the growth rate of structure up to galaxy scales.

Entanglement bootstrap (EB) is a framework that aims to explain all the universal properties of quantum phases of matter from entanglement conditions. In this seminar, I will talk about our efforts in building such an EB framework for 2+1D chiral gapped phases. Many interesting properties that do not exist in non-chiral gapped states, such as robust gapless boundary and sharp corner contributions in entanglement entropies, can be derived in this framework. To capture the algebraic relations among local entanglement Hamiltonians, we defined a quantum-information-theoretic primitive called instantaneous modular flow. We then derived several instantaneous modular-flow equations that generalize the well-known formulas of topological entanglement entropy and chiral central charge. If time permits, I will also discuss a few applications of EB in conformal field theories in both 1+1D and 2+1D with fuzzy sphere.

Inflaton couplings during warm inflation result in the production of a thermal bath. Thermal fluctuations can dominate the standard de Sitter analogues, resulting in a modified slow-roll scenario with a new source of density fluctuations. It is generally difficult to reliably calculate the predictions of warm inflation, and therefore assess its viability as a model of the early universe. We will present a fully calculable perturbative model of warm inflation, and discuss its main features. We will see that the thermal bath develops a chemical potential. The chemical potential has a rather large impact, and in extreme cases the chemical potential can stop warm inflation from happening all together.