A light scalar from walking solutions in gauge-string duality

TL;DR

This paper investigates a specific gauge-string duality background with walking behavior, computing scalar fluctuation spectra that reveal a light dilaton candidate due to approximate scale invariance.

Contribution

It numerically analyzes scalar spectra in a walking gauge theory background, identifying a light scalar consistent with a dilaton, which is a novel feature in this class of solutions.

Findings

Spectrum contains a light scalar with suppressed mass

Spectral features include cuts and poles near branch points

Supports the interpretation of a dilaton as a pseudo-Goldstone boson

Abstract

We consider the type-IIB background generated by the strong-coupling limit of Nc D5 branes wrapped on S2, and focus our attention on a special class of solutions that exhibit walking behavior. We compute numerically the spectrum of scalar fluctuations around vacua of this class. Besides two cuts, and sequences of single poles converging on one of the branch points, the spectrum contains one isolated scalar, the mass of which is suppressed by the length of the walking region. Approximate scale-invariance symmetry in the walking region suggests that this be interpreted as a light dilaton, the pseudo-Goldstone boson of dilatations.