58th North British Mathematical Physics Seminar

Abstract: The plaquette Ising model with spins living on the vertices a 3D cubic lattice has appeared in various contexts ranging from discrete models of surfaces to the study of fractons, which are quasiparticle excitations with restricted mobility. We discuss the model's history, noting along the way that insisting numerical results running contrary to your prejudices obtained by PhD students must necessarily be wrong is not always wise.

Abstract: I will deduce an action for M5-branes by considering M-theory on AdS7xS4 and reducing the AdS7 factor along a timelike Hopf fibration. The resulting boundary theory has 24 supercharges and a Lifshitz scaling symmetry and can be understood as the M5-bane theory reduced along a compact null direction. This talk is based on 1904.07547 and 1912.02638.

Abstract: A possible resolution to the fine tuning problem of the cosmological constant is via the anthropic principle, which roughly states that the observed fine tuning is only a result of a selection bias. To realise this idea in string theory, string theorists built a vast landscape of 4D string de Sitter vacua of which our universe is one. The punchline is that, upon rigorous inspections, there is not a single uncontroversial de Sitter vacuum in string theory, let alone a landscape. In this talk, we shall discuss a few aspects of the famous KKLT construction of string de Sitter vacua. In particular, using the blackfold approach, we shall discuss properties (existence, classical stability, and thermal transition) of antibranes metastable states in fluxed throats, a controversial yet essential ingredient of the KKLT construction.