David Anthony Lowe

Brown University
Holographic approaches to gravity and the arrow of time

A promising approach to string theory and quantum gravity has been developed over the past decade. Quantum gravity in spacetimes with a negative cosmological constant can be reformulated in terms of special quantum field theories without gravity, in a spacetime with one fewer dimension. This is an example of a holographic reformulation of quantum gravity. In principle, these lower dimensional quantum field theories provide complete formulations of string theory, which previously had only existed as a series expansion in small fluctations around special spacetime backgrounds. In practise, it has been challenging to decode the hologram to address questions in quantum gravity. This project will develop ways to embed realistic cosmologies within this framework, and use new tools to decode the hologram. The goal is to find new insights into the origin of the arrow of time and the quantum nature of spacetime geometry.

The conjecture that a gravitational theory with negative cosmological constant can be dual to a lower dimensional conformal field theory provides us with a new set of tools to address fundamental questions in quantum gravity. In this framework, there is a well-defined notion of continuous global time, while at the same time, there is a sense in which the spacetime of the gravitational theory is discrete due to quantum effects. The primary goal of the project is to address how cosmological time emerges from the conformal field theory description, by studying the embedding of inflating cosmological bubbles within an asymptotically negative cosmological constant background. Preliminary results indicate an arrow of time emerges because quantum consistency conditions single out time asymmetric bubbles. The project will seek direct evidence of this phenomena within conformal field theories, and attempt to develop simple models of large N systems that exhibit an arrow of time via this mechanism. The project will also study how the spacetime background is reconstructed from the conformal field theory description in a more general context, which will provide new insights into the nature of quantum spacetime geometry.

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