Search Talks

We classify quantum states proximate to the semiclassical Neel state of the spin S=1/2 square lattice antiferromagnet with two-spin near-neighbor and four-spin ring exchange interactions. Motivated by a number of recent experiments on the cuprates and the iridates, we examine states with Z_2 topological order, an order which is not present in the semiclassical limit. Some of the states break one or more of reflection, time-reversal, and lattice rotation symmetries, and can account for the observations. We discuss implications for the pseudogap phase.

An overview will be given of recently discovered connection between asymptotic symmetries in general relativity  and soft theorems in quantum field theory together with their implications for the black hole information paradox.

We study the boundary conditions in the topologically twisted Chern-Simons matter theories with the Lie 3-algebraic structure. We find that the supersymmetric boundary conditions and the gauge invariant boundary conditions can be unified as the complexified gauge invariant boundary conditions which lead to the supergroup WZW models. We examine the BPS indices of the supergroup WZW models which may describe certain junctions of M2-branes and M5-branes by identifying the vacuum configurations of the brane system with the weight diagrams of the associated Lie superalgebras. For the case arising from the BLG model an explicit expression can be given in terms of a mock modular form. We will also consider the alternative matrix quantum mechanical descriptions of the supergroup WZW models. The talk will be based on recent works arXiv:1512.06646, arXiv:1612.07565 and ongoing research.

Fast Radio Bursts are mysterious radio flashes that appear to have extragalactic origin. The inferred isotropic brightness temperature for these events can exceed 10^34 K. Discovered in 2006, only about 25 have been reported to date. I will give a short summary of the these events then explain how a new generation of dense radio arrays will dramatically improve our understanding of these burst. The HIRAX telescope in South Africa will detect about 10 FRBs per day and will localize these events with sub-arcsecond precision. A next generation of packed array could detect one every minute, allowing tomography of the ionized universe.