Talks

We analyse a class of 1D lattice models, known as M_k models, which are characterised by an order-k clustering of spin-less fermions and by N=2 lattice supersymmetry. We show a fundamental connection to Z_k parafermions and identify a class of (bulk or edge) defects, which are in one-to-one correspondence with so-called spin fields in the parafermion CFT. In the gapped regime, injecting such defects leads to ground state degeneracies that are protected by the supersymmetry. The defects, which are closely analogous to quasi-holes over the fermonic Read-Rezayi quantum Hall states, display characteristic fusion rules, which are of Ising type for k=2 and of Fibonacci type for k=3.

To best distinguish between classical and non-classical models of nature requires a good notion of classicality. I will argue that noncontextuality is a good candidate for this notion. Until now, certain theoretical and experimental roadblocks have stood in the way of a test of noncontextuality which is free of unattainable experimental idealizations. I will present solutions to these roadblocks as well as the results of an experimental test.

Based on results in quantum gravity we conjecture a sharp bound on the rate of growth of chaos in thermal quantum systems with a large number of degrees of freedom. Chaos can be diagnosed using an out-of-time-order correlation function closely related to the commutator of operators separated in time. We conjecture that the influence of chaos on this correlator can develop no faster than exponentially, with Lyapunov exponent λL ≤ 2πkBT/\hbar. We give a precise mathematical argument, based on plausible physical assumptions, establishing this conjecture. 

In relativistic quantum information (RQI) we study quantum information in relativistic systems to obtain more insights to both quantum and gravitational physics on the one hand, and to find new ideas for quantum information processing on the other. One of the  popular models in RQI is the Unruh-DeWitt (UD) detector theory, in which localized objects, called detectors, are coupled to and moving in relativistc quantum fields. In this mini-course I will discuss the UD detector theory in detail, mainly on the nonperturbative methods and their applications to RQI.

There have been recent claims that the weak gravity conjecture (WGC) rules out multi-field natural inflation. I review these claims and then show how 2-field natural inflation can be consistent with even the most stringent form of WGC. I also discuss my recent attempt at numerically proving the WGC via the conformal bootstrap.