Topological defects in thermodynamic phases are characterized by winding
numbers of order parameters. Similarly, topological phases in the tenfold
classification of insulators and superconductors are characterized by Chern and
winding numbers. We show that both situations can be described by a single
formalism, using…

In 1974 Purcell authored a paper “Life at Low Reynolds Number” to describe the counterintuitive world of microscopic organisms in which viscous dissipation so dominates inertia that “coasting” is impossible, and that the geometry of a path in an internal movement space dominates self-propulsion. It is typically assumed that a key difference…

 Post-inflationary QCD axion is an attractive solution to the Strong CP problem because of the possibility to uniquely predict the axion mass if axion makes up all of dark matter. On the other hand, QCD axion models often suffer from the so-called axion quality problem, where the axion shift symmetry is…

The cosmic microwave background (CMB) is a powerful probe into the history of our universe. The Simons Observatory (SO) is a currently-deploying CMB survey located in the Atacama Desert in Chile at an elevation of 5200 meters, consisting of an array of three 0.42-meter small aperture telescopes (SATs) and one 6-meter…

Decades of direct, indirect and collider searches of dark matter have set stringent constraints pushing us to entertain the possibility that dark matter interacts with us purely gravitationally. In this nightmare scenario, the underlying particle physics of dark matter as well as our cosmological history could still be discerned purely…

String stars, or Horowitz-Polchinski solutions, are string theory saddles with normalizable condensates of thermal-winding strings. In the past, string stars were offered as a possible description of stringy (Euclidean) black holes in asymptotically flat spacetime, close to the Hagedorn temperature. I will discuss the…

Strong interactions between electrons in solids lead to emergent quantum phenomena that can unveil important principles of physics. Recently, the observation of superconducting and correlated insulator states in magic-angle twisted bilayer graphene has promoted two-dimensional van der Waals heterostructures as a novel platform for studying…

Two-dimensional materials, analogous to Lego on the atomic scale, offer unprecedented opportunities for designing exotic quantum phases through gating, stacking, and angle twisting. The unrivaled tunability gives rise to the flat electronic bands of moiré and crystalline graphene, promoting various correlated states including unconventional…

The Fractional Quantum Hall effect is one of the most fundamental phenomena of quantum physics. Under a very large magnetic field, and at fractional filling of a Landau level, when electrons are “supposed” (by simple band theory) to form a metal, one finds a gapped insulating state that is “topologically ordered” and hosts a huge array of…

Ultracold polar molecules provide a unique platform for simulating quantum many-body systems with long-range interactions. However, their complex internal structures and susceptibility to collisional losses present a significant challenge in both cooling them to quantum degeneracy and controlling their interactions. In this talk, I will present…

The discovery of the neutrino stands as pivotal milestone in the annals of modern physics. Following the initial detection of neutrinos, a diverse array of experiments employing both natural and artificial sources of neutrinos have played a crucial role in shedding light on the elusive nature of these particles, including their intriguing…

I will discuss how symmetries of quantum spin systems can be realized. For a given realization of a symmetry group G of a 1d spin system, I will define the anomalous index that takes values in the cohomology H^4(BG) of the classifying space of the group. I will show that a G-invariant system with a non-trivial anomalous index can not have a…