Naturalness of exponential cosmon potentials and the cosmological constant problem

TL;DR

This paper explores how exponential quintessence potentials relate to dilatation symmetry and discusses higher-dimensional models that address the cosmological constant problem while maintaining stable particle physics properties.

Contribution

It links exponential quintessence potentials to anomalous dilatation symmetry and proposes higher-dimensional scenarios for a small, stable cosmological constant.

Findings

Almost flat scalar field directions linked to dilatation symmetry.

Higher-dimensional models can naturally lead to a small cosmological constant.

Quantum fluctuations are considered in the context of the cosmological constant.

Abstract

We discuss the naturalness of exponential potentials for quintessence, showing that the resulting almost flat direction in the space of scalar fields, as well as the small time dependent cosmon mass, can be related to an anomalous dilatation symmetry. We argue that the physics of the cosmological constant is Planck scale physics, and comment on the role of quantum fluctuations. We present three higher dimensional scenarios how a runaway of the ``cosmological constant'' to zero can be combined with stable particle physics properties, leading at most to small variations of the ``fundamental couplings''.