To the Horizon and Beyond Unitary evolution and non-universal dynamics of horizons in holography

Within our Universe, horizons are elusive objects. They appear around black holes, where they denote the ‘point of no return’, and in cosmology, where they form the end of what we can see due to the accelerated expansion of space. Both horizons are intrinsically quantum-gravitational, and hence a proper understanding should teach us about aspects of quantum gravity. This dissertation studies both horizons, using two-dimensional holography as its main tool. It broadly follows two routes.
The first route considers the information problem, originally formulated for black holes: does the radiation emitted by a horizon contain the information that has fallen behind it? I develop a new model to study this problem for a black hole horizon, and then apply it to the cosmological horizon.
In the second route, I focus on black hole horizons of various types: five-dimensional rotating, and four-dimensional charged black holes, embedded in flat or curved spacetime. Many (macroscopic) properties of black holes, such as their entropy, are universal; this suggests that there is a commonality in their statistical description. In this dissertation I classify non-universal aspects of black holes that are encoded in deformations away from an idealized near-horizon geometry. Such aspects are crucial when designing microscopic descriptions---relevant for our overarching aim of understanding quantum gravity.
Within both routes, the final aim is to carefully construct microscopic duals. I conclude this dissertation by contemplating the lessons learned, and with a speculative outlook on these directions, which I believe are both relevant for a better understanding of our own Universe.