Dilaton stabilization by massive fermion matter

TL;DR

This paper extends previous work on Dilaton stabilization by including three-loop corrections, showing the Dilaton tends to be fixed near the Planck scale with a high mass, implying no detectable scalar signals in current cosmology.

Contribution

It provides a three-loop correction analysis for Dilaton stabilization, confirming the high-scale fixed point and mass, and discusses the validity of the Yukawa model approximation.

Findings

Dilaton vacuum field stabilizes near the Planck scale.

Dilaton mass is close to the Planck mass, suppressing observable signals.

Three-loop corrections reinforce previous two-loop results.

Abstract

The study started in a former work about the Dilaton mean field stabilization thanks to the effective potential generated by the existence of massive fermions, is here extended. Three loop corrections are evaluated in addition to the previously calculated two loop terms. The results indicate that the Dilaton vacuum field tend to be fixed at a high value close to the Planck scale, in accordance with the need for predicting Einstein gravity from string theory. The mass of the Dilaton is evaluated to be also a high value close to the Planck mass, which implies the absence of Dilaton scalar signals in modern cosmological observations. These properties arise when the fermion mass is chosen to be either at a lower bound corresponding to the top quark mass, or alternatively, at a very much higher value assumed to be in the grand unification energy range. One of the three 3-loop terms is exactly evaluated in terms of Master integrals. The other two graphs are however evaluated in their leading logarithm correction in the perturbative expansion. The calculation of the non leading logarithmic contribution and the inclusion of higher loops terms could made more precise the numerical estimates of the vacuum field value and masses, but seemingly are expected not to change the qualitative behavior obtained. The validity of the here employed Yukawa model approximation is argued for small value of the fermion masses with respect to the Planck one. A correction to the two loop calculation done in the previous work is here underlined.