Brane Worlds, the Cosmological Constant and String Theory

TL;DR

This paper explores how brane world scenarios within string theory frameworks can naturally allow flat four-dimensional spacetime solutions by choosing integration constants, addressing the cosmological constant problem.

Contribution

It demonstrates that brane world models can provide a string-inspired mechanism for flat spacetime solutions through parameter choices, unlike traditional compactification methods.

Findings

Brane world scenarios permit flat solutions via integration constants.

Gauged supergravity can realize brane world models compatible with string theory.

Potential string theory realization of brane world solutions to the cosmological constant problem.

Abstract

We argue that traditional methods of compactification of string theory make it very difficult to understand how the cosmological constant becomes zero. String inspired models can give zero cosmological constant after fine tuning but since string theory has no free parameters it is not clear that this is allowed. Brane world scenarios on the other hand while they do not answer the question as to why the cosmological constant is zero do actually allow a choice of integration constants that permit flat four space solutions. In this paper we discuss gauged supergravity realizations of such a world. To the extent that this starting point can be considered a low energy effective action of string theory (and there is some recent evidence supporting this) our model may be considered a string theory realization of this scenario.