Astrophysics

The Baryon Acoustic Oscillations (BAO) are the latest weapon in the quest for precision cosmology and dark energy. Many presentations on BAO are complicated and unclear and I will therefore present BAO with particular emphasis on trying to give the simplest theoretical description, both at the linear and nonlinear level, and will describe some of the observational challenges to measuring BAO.

Recently there has been renewed interest in cosmological gravity, namely 3d gravity coupled to a Chern-Simons term with parameter $\mu$, following claims that at $\mu =1$ the theory becomes chiral and stable. In this talk we will investigate cosmological gravity by setting up a concrete holographic dictionary with a dual 2d field theory and we will demonstrate that the theory is in fact not chiral in the limit $\mu = 1$. Instead our holographic dictionary implies that at $\mu =1$ the dual field theory becomes a logarithmic CFT (LCFT). Our results resolve confusions in the earlier literature and the resulting new class of holographic dualities involving LCFTs may have interesting applications to strongly correlated condensed matter systems.

Cosmological bubble collisions arising from first order phase transitions are a generic consequence of the Eternal Inflation scenario. I will present our computational strategy for generating and evolving these bubbles in 3+1 dimensions and in a self-consistently expanding background. I will show the existence of classical field transitions--the classical nucleation of bubbles during collisions--which can dramatically alter the canonical description of eternal inflation.

We propose a holographic description of four dimensional single scalar inflationary universes, in particular asymptotically de Sitter cosmologies and power-law inflation. We show how cosmological observables such as the primordial power spectrum and non-gaussianities are encoded in correlation functions of a three dimensional QFT.

In Randall-Sundrum single-brane (RS-II) model, it was conjectured that there is no static large black hole localized on the brane based on adS/CFT correspondence. Here we consider the phase diagram of black objects in the models extended from the RS-II model. We propose a scenario for the phase diagram consistent with the classical black hole evaporation conjecture. The proposed scenario indicates the existence of a rich variety of the families of black objects. We present several side evidences that support the whole picture.