An AdS/QCD model from tachyon condensation: II

Abstract

A simple holographic model is presented and analyzed that describes chiral symmetry breaking and the physics of the meson sector in QCD. This is a bottom-up model that incorporates string theory ingredients like tachyon condensation which is expected to be the main manifestation of chiral symmetry breaking in the holographic context. As a model for glue the Kuperstein-Sonnenschein background is used. The structure of the flavor vacuum is analyzed in the quenched approximation. Chiral symmetry breaking is shown at zero temperature. Above the deconfinement transition chiral symmetry is restored. A complete holographic renormalization is performed and the chiral condensate is calculated for different quark masses both at zero and non-zero temperatures. The 0^{++},0^{-+},1^{++},1^{--} meson trajectories are analyzed and their masses and decay constants are computed. The asymptotic trajectories are linear. The model has one phenomenological parameter beyond those of QCD that affects the 1^{++},0^{-+} sectors. Fitting this parameter we obtain very good agreement with data. The model improves in several ways the popular hard-wall and soft wall bottom-up models.Comment: 55 pages, 17 figures, 8 appendice

On finite-temperature holographic QCD in the Veneziano limit

“…The starting point of our finite temperature analysis is the T = 0 holographic model introduced in [26], based on previous theoretical ideas in [30][31][32][33][34][35][36][37][38][39][40]. Moving to finite T implies studying black hole solutions of the action in [26].…”

“…The other scalar, the "tachyon" τ , is dual to the quark mass operatorqq. The potentials and interactions were modeled along successful bottomup models for YM, namely Improved Holographic QCD (IHQCD) [30][31][32][33][34][35][36] and the idea that string theory tachyon condensation describes chiral symmetry breaking [37][38][39][62][63][64][65].…”

“…For the dilaton this has been settled in [30][31][32][33][34][35]. For the tachyon the notion of regularity is different and has been studied in detail in [38,39].…”

“…and for them the leading divergence is 39) where the constant C is again known and now r 1 parametrises the solutions. To select this solution, it is required that the last term in the square brackets in (2.38) grows faster than λ 4/3 .…”

Vector-axial vector correlators in weak electric field and the holographic dynamics of the chiral condensate

“…It has been proposed that the non-linear DBI-like actions proposed by Sen and others are the proper setup in order to study the holographic dynamics of chiral symmetry breaking, [15]. This dynamics was analyzed in a toy example, [16,17], improving several aspects of the hard [19,20], and soft wall models, [21]. We will keep referring to T as the "tachyon", as it indeed corresponds to a relevant operator in the UV.…”