Holographic gauged NJL model and applications

Abstract

There are two models of spontaneous chiral symmetry breaking in strongly coupled gauge theories. The symmetry can be broken when a chiral condensate is formed by the non-abelian gauge interactions in the ”natural” QCD vacuum or the condensate can be generated or enhanced by the inclusion of a Nambu-Jona-Lasinio (NJL) term. We study the effect of both of these using AdS/CFT, a strong-weak duality which allows us to transform the gauge theory calculations into a problem of D brane embeddings in an AdS spacetime. This model, termed dynamic AdS/QCD, is then applied to technicolour. Technicolour is a phenomenological theory of electroweak symmetry breaking in which the chiral symmetry breaking mechanism of a new QCD-like sector is exploited to provide the electroweak symmetry breaking mechanism. We first apply the dynamic AdS/QCD theory to studying the physical QCD meson spectrum both with and without four fermion interactions in chapter 4. Next we turn our attention to technicolour. In chapter 5 we discuss extended technicolour using an NJL term to enhance the top mass. While in chapter 6 we discuss ideal walking theories where the theory remains strongly coupled over a large range of scales.

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