A Naturally Small Cosmological Constant on the Brane?

TL;DR

This paper explores how brane-world models in higher-dimensional spacetime might naturally explain the smallness of the cosmological constant, offering potential solutions to a longstanding problem in physics.

Contribution

It highlights unique features of brane models, such as supersymmetry breaking and hidden low-energy degrees of freedom, that could account for a small but non-zero cosmological constant.

Findings

Cosmological constant can be naturally suppressed by weak coupling constants.

Models allow for a small, non-zero cosmological constant consistent with observations.

Potential for low-energy degrees of freedom to be hidden on different branes.

Abstract

There appears to be no natural explanation for the cosmological constant's small size within the framework of local relativistic field theories. We argue that the recently-discussed framework for which the observable universe is identified with a p-brane embedded within a higher-dimensional `bulk' spacetime, has special properties that may help circumvent the obstacles to this understanding. This possibility arises partly due to several unique features of the brane proposal. These are: (1) the potential such models introduce for partially breaking supersymmetry, (2) the possibility of having low-energy degrees of freedom which are not observable to us because they are physically located on a different brane, (3) the fundamental scale may be much smaller than the Planck scale. Furthermore, although the resulting cosmological constant in the scenarios we outline is naturally suppressed by weak coupling constants of gravitational strength, it need not be exactly zero, raising the possibility it could be in the range favoured by recent cosmological observations.