Talks

In this talk, I attempt to gain insight into the description of quantum gravity on cosmological spacetimes by considering the physics of families of accelerating observers in spacetimes which admit non-perturbative descriptions vis AdS/CFT.

I will discuss the techniques that can be used to include arbitrary equations of state in MHD simulations, particularly the ways in which one may perform conservative to primitive variable conversion numerically for such simulations.

GPUs can offer a less costly solution to large-scale calculations of astrophysical systems. I will outline the basics of the CUDA libraries and also compare with various metrics our in-development GPU code for molecular dynamics versus our hybrid OpenMP/MPI version.

I will explain how Liouville theory with complex values of its parameters arises naturally in speculative holographic cosmologies. We will encounter Liouville theory of both the ``spacelike'' and ``timelike'' variety. I will then use this as motivation to present some new results on the analytic continuation of Liouville theory recently obtained with Maltz and Witten.

I discuss bubble collisions from the perspective of an observer in a hat. In particular, I emphasize the breaking and restoration of conformal symmetry, as well as (independence of) initial conditions and rate equations. A cartoon version of the problem, Mandelbrot percolation, makes computations tractable. Enjoyable, even.

Motivated by the consistency of black hole complementarity, Sekino and Susskind have conjectured that no physical system can "scramble" its internal degrees of freedom in time faster than (1/T) log S, where T is temperature and S the system's entropy. By considering a number of toy examples and general Lieb-Robinson-type causality bounds, I'll explore the range of validity of the conjecture. Some of these examples suggest that nonlocal Hamiltonians can delocalize information at rates exceeding the fast scrambling bound, but the physical relevance of these examples is unclear. Joint work with Nima Lashkari and Douglas Stanford.

We investigate a simple FRW spacetime realized by a brane construction. This also comes from a Coleman-de Luccia decay from a metastable de Sitter. We motivate a dual description in terms of a low energy effective field theory (EFT) on FRW in one lower dimensions. This EFT is coupled to gravity with a time-dependent Planck mass that grows to infinity at late times. We investigate the entropy bound, correlation functions, and various particle/brane probes as first steps to understand the degrees of freedom building up the EFT. This is work in collaboration with B. Horn, S. Matsuura, E. Silverstein, and G. Torroba.

I will discuss recent work engineering "semi-holographic" constructions of de Sitter space in string theory, using elliptic fibrations and orientifolds to uplift known Freund-Rubin compactifications. The dual brane construction is compact and provides a microscopic realization of the dS/dS correspondence of Alishahiha et al., realizing de Sitter space in d dimensions as a warped compactification down to d-1 dimensional de Sitter space coupled to a pair of large N matter sectors. This provides a parametric microscopic accounting of the Gibbons-Hawking entropy. I will discuss an explicit example in three dimensions as well as ongoing work in four dimensions.