Mesons in gauge/gravity duals

Abstract

Abstract. We review recent progress in studying mesons within gauge/gravity duality, in the context of adding flavour degrees of freedom to generalizations of the AdS/CFT correspondence. Our main focus is on the "top-down approach" of considering models constructed within string theory. We explain the stringtheoretical constructions in detail, aiming at non-specialists. These give rise to a new way of describing strongly coupled confining large-N gauge theories similar to large-N QCD. In particular, we consider gravity dual descriptions of spontaneous chiral symmetry breaking, and compare with lattice results. A further topic covered is the behaviour of flavour bound states in finite-temperature field theories dual to a gravity background involving a black hole. We also describe the "bottom up" phenomenological approach to mesons within AdS/QCD. Some previously unpublished results are also included.PACS. 11.15.-q Gauge field theories -11.25.Tq Gauge/string duality -12.40.Yx Hadron mass models and calculations -14.40.-n Mesons

Introductory lectures to large- QCD phenomenology and lattice results

“…[28] and references therein for an extensive discussion). For example, it is possible to modify the setup discussed above, by including a set of n f D7-branes [43] ("flavor branes"), with which one can mimic a set of quark fields (in the fundamental representation of the gauge group) of different flavors.…”

Holographic quark gluon plasma with flavor

“…since it is invariant under compactification. The constantx 25 is arbitrary since it cancels in the whole solution (2.7). Only the zero mode is affected by the compactification since the momentum becomes p 25 = K/R with K labeling the levels of the Kaluza-Klein tower of excitations becoming massive upon compactification.…”

“…In order to come closer to a QCD-like behavior we therefore investigate how to incorporate quarks and their bound states in this section. We focus on the main results of [36] and [38], however for a concise review the reader is referred to [25].…”

“…Unfortunately there is no version of the correspondence available which realizes QCD or even the whole standard model to date. At the moment one relies on the fact that studying other strongly coupled gauge theories one still learns something about strongly coupled dynamics in general and maybe even of QCD in particular if one studies features with a sufficient generality or universality, such as meson mass ratios [25] or the shear viscosity to entropy ratio of a strongly coupled thermal plasma [9].…”

“…So far the effect of finite chemical baryon potential in the gauge theory and the structure of the phase diagram of these theories have been explored. For a review of the field the reader is referred to [25], while a brief introduction can also be found here in section 2.3. This connection between introducing fundamental matter and the exploration of its thermodynamic an hydrodynamic properties in the strongly coupled thermal gauge theory as well as the extension to more general chemical potentials is central to my work partly published in [1,2].…”