5th DAE-BRNS Workshop on Hadron Physics (Hadron 2011) IOP Publishing Journal of Physics: Conference Series 374 (2012) 012004 doi:10.1088/1742-6596/374/1/012004 Hadron physics in holographic QCD A. B. Santraa, U. Lombardob, A. Bonannoc a Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India. b INFN-LNS and University of Catania, 44 Via S.-Sofia, I-95125 Catania, Italy. c INAF- Catania Astrophysical Observatory, Via S.Sofia 78, 95123 Catania, Italy. E-mail:
[email protected] Abstract. Hadron physics deals with the study of strongly interacting subatomic particles such as neutrons, protons, pions and others, collectively known as baryons and mesons. Physics of strong interaction is difficult. There are several approaches to understand it. However, in the recent years, an approach called, holographic QCD, based on string theory (or gauge-gravity duality) is becoming popular providing an alternative description of strong interaction physics. In this article, we aim to discuss development of strong interaction physics through QCD and string theory, leading to holographic QCD. 1. Introduction The accepted theory of strong nuclear forces, or strong interactions, is Quantum Chromodynamics (QCD) [1], an Yang-Mills gauge theory with SU(3) gauge group. It can be studied at high energies using perturbation theory with enormous success, but, it is very hard, known to be intractable for the analytical analysis at low energies because of the strong coupling problem. The low energy regime of QCD contains the most interesting phenomena related to hadron physics, thus it is of great theoretical interest. Due to unavailability of suitable analytical tools for understanding QCD in the non-perturbative regime, QCD inspired heuristic models and approximation schemes, ranging from the bag models [2, 3] to chiral perturbation theory [4, 5] have been used to get partial information about the dynamics of QCD in the strongly coupled regime.