Talks

The eternal inflation scenario predicts that our observable universe resides inside a single bubble embedded in a vast inflating multiverse. Collisions between bubble universes imprinted in the CMB sky provide a powerful observational test of this idea. I will describe a robust algorithm for non-Gaussian source detection in massive datasets, and present its application to the search for bubble collision signatures in CMB data from WMAP.

The Large Hadron Collider was recently switched on, then broke and was switched on again. It has started producing collisions that probe Nature on the smallest distances yet reached. What broke when it was switched on? How does one detect what comes out of these collisions, and what can the result tell us about how Nature works on these scales? This talk briefly describes what we think we know, why it may be wrong, and whether (in either case) it will destroy the world.

String theory should give a well-defined answer to the following question: What is the state of matter in the limit of infinite energy density? We use results obtained from the understanding of black hole entropy to conjecture this equation of state, noting that the maximum entropy state in string theory has vastly more entropy than the states used in traditional approaches to early Universe Cosmology. The evolution of the Universe with this equation of state can be obtained in closed form.

A serious shortcoming of spinfoam loop gravity is the absence of matter. I present a minimal and surprisingly simple coupling of a chiral fermion field in the framework of spinfoam quantum gravity. This result resonates with similar ones in early canonical loop theory: the naive fermion hamiltonian was found to be just the extension of the simple

It is argued that the correct quantization of a scalar field theory in de Sitter spacetime involves a de Sitter invariant state which is not the Bunch-Davies vacuum. A novel but natural de Sitter invariant alternative exists and it is suggested that this and is the prefered state for scalar field theories. The argument is based on the exact solution of an interacting scalar field theory.

In the context of the AdS/CFT correspondence, I will discuss model-independent properties shared by bulk theories of gravity with consistent dual descriptions. I will then discuss the prospects of extending these ideas to non-conformal theories, in particular to attempts to realize cosmological theories holographically. I will address the status of in-principle falsifiability of various holographic proposals through internal consistency conditions of the boundary theory.

FRW/CFT duality is a proposal for a holographic dual description for universe created by bubble nucleation. For (3+1) dimensional universe, the dual theory is defined on 2-sphere at the boundary of open universe. I will study correlation functions and explain essential features of FRW/CFT duality: One bulk field corresponds to a tower of CFT operators The boundary theory contains 2D gravity, and the Liouville field plays the role of time. Energy-momentum tensor has dimension 2, as required from the 2D conformal symmetry.