Search Talks

Weak gravitational lensing is a highly valued tool for inferring the structure of the spacetime metric between an observer and a cosmologically distant “wallpaper,” most commonly either the CMB or faint background galaxies. The best-measured quantities are the second derivatives of the projected scalar potential(s), which are manifested as apparent shearing and magnification of the wallpaper.  Given a collection of faint-galaxy images, what information can we extract about the shear and magnification that these images have undergone?  I will describe a new method of lensing inference that, unlike predecessors, is rigorously correct in the presence of noise and other observational realities, nearly optimal, and computationally feasible at the scale of current/future surveys like the Dark Energy Survey and the Large Synoptic Survey Telescope.

It has become a platitute to say that black holes are fascinating objects—but they really are, in part because they challenge our understanding of the fundamental reversibility of physical processes.

In the first part of the talk, I will review some of the classical ways black holes behave as dissipative systems, such as the "hair loss” phenomenon and the monotonic growth of horizon area. In the second part, I will explain how quantum mechanics (more precisely, the coupling of black holes to the quantum vacuum) affects the classical picture at late times, notably through particle creation and evaporation. I will argue that techniques from two-dimensional field theory can help bring clarity to the associated “information loss”

problem, and perhaps also point to new, unexpected predictions. My approach will be as model-independent as possible; that is, rather than investigating a particular scenario for black hole evaporation, I will aim to derive generic consequences from basic assumptions regarding the reversibility of black hole evaporation.