On hadrons and inflatons: the holography of strongly coupled processes

Abstract

Strong coupling presents problems for traditional quantum field theory as it escapes the purview of perturbation theory. The last decade has seen the emergence of a new tool to tackle such problems, arising from a new string duality that was discovered in the last years of the twentieth century. Gauge/gravity duality (or the AdS/CFT Correspondence) translates weakly coupled supergravity to strongly coupled gauge theory. The duality is holographic in that the field theory can be considered to reside on the boundary of the bulk space that hosts the gravitational theory. In this thesis, I will provide background to this theory, reviewing the theory behind QCD, string theory and the AdS/CFT Correspondence. I will then present two new applications of the Correspondence. Firstly, I will present a model of hadronization (a problem of strongly coupled QCD), in which separating quarks are envisioned holographically as the endpoints of a string which lie on a D7-brane – the brane is embedded in a dilaton-flow geometry that exhibits such QCD-like properties as confinement. Upon breaking the string at its midpoint and reattaching it to the brane, a kink is imposed, which propagates to the end of the string and quickly jerks the endpoint. This in turn leads to the radiation of a worldvolume gauge field, which is dual to rho mesons in the field theory. In the second work, I will apply the Correspondence to the problem of cosmological inflation. In particular, I will consider the case of an inflaton formed as a composite scalar in a strongly coupled gauge theory. Holography then allows us to study the time dependence of the development of this condensate and to see which aspects of running coupling are conducive to slow-roll inflation

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