Glueball Spectra from Gauge-Gravity Duality

In this talk, we present a very general formalism for the holographic computation of glueball spectra that is applicable to a large number of systems, either obtainable from string theory, or within the context of bottom-up effective field theory constructions. Using this formalism, we study a few examples (both from string theory as well as simpler toy models) chosen so as to be of relevance to theories with so-called walking behaviour, i.e. theories for which the gauge coupling stays approximately constant over a large intermediate energy regime. In particular, we address the question of whether the spectra of such theories contain a parametrically light scalar, present due to the spontaneous breaking of approximate scale invariance.