Eur. Phys. J. A (2008) 35: 81-133
https://doi.org/10.1140/epja/i2007-10540-1

Review

Mesons in gauge/gravity duals

¹ Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805, München, Germany
² School of Physics and Astronomy, Southampton University, S017 1BJ, Southampton, UK
³ Isaac Newton Institute for Mathematical Sciences, 20 Clarkson Road, CB3 0EH, Cambridge, UK
⁴ Institut für Theoretische Physik, ETH Zürich, CH-8093, Zürich, Switzerland

^* e-mail: jke@mppmu.mpg.de

Received: 14 December 2007
Accepted: 9 January 2008
Published online: 27 February 2008

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 string-theoretical 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 Some previously unpublished results are also included.