Eur. Phys. J. C (2014) 74: 2790
https://doi.org/10.1140/epjc/s10052-014-2790-x

Regular Article - Theoretical Physics

A naturally light dilaton and a small cosmological constant

¹ Institut de Physique Théorique, CEA-Saclay, 91191 , Gif-sur-Yvette Cedex, France
² Dipartimento di Fisica e Astronomia, Università di Padova and INFN, Sezione di Padova, Via Marzolo 8, 35131 , Padua, Italy
³ Department of Physics, LEPP, Cornell University, Ithaca, NY, 14853, USA
⁴ Department of Physics, Syracuse University, Syracuse, NY, 13244, USA
⁵ Department of Physics, University of California, Davis, CA, 95616, USA

^* e-mail: b.bellazzini@gmail.com
^** e-mail: brando.bellazzini@cea.fr

Received: 21 June 2013
Accepted: 18 February 2014
Published online: 15 March 2014

Abstract

We present a non-supersymmetric theory with a naturally light dilaton. It is based on a 5D holographic description of a conformal theory perturbed by a close-to-marginal operator of dimension which develops a condensate. As long as the dimension of the perturbing operator remains very close to marginal (even for large couplings) a stable minimum at hierarchically small scales is achieved, where the dilaton mass squared is suppressed by . At the same time the cosmological constant in this sector is also suppressed by , and thus it is parametrically smaller than in a broken SUSY theory. As a byproduct we also present an exact solution to the scalar-gravity system that can be interpreted as a new holographic realization of spontaneously broken conformal symmetry. Even though this metric deviates substantially from AdS space in the deep IR it still describes a non-linearly realized exactly conformal theory. We also display the effective potential for the dilaton for arbitrary holographic backgrounds.