Quantum and stringy corrections to the equation of state of holographic QCD matter and the nature of the chiral transition

Abstract

We consider the finite temperature phase diagram of holographic QCD in the Veneziano limit (N c → ∞, N f → ∞ with x f = N f /N c fixed) and calculate one string-loop corrections to the free energy in certain approximations. Such corrections, especially due to the pion modes are unsuppressed in the Veneziano limit. We find that under some extra assumptions the first order transition following from classical gravity solutions can become second order. If stringy asymptotics are of a special form and there are residual interactions it may even become of third order. Operationally these computations imply modelling the low temperature chiral symmetry breaking phase with a hadron gas containing N 2 f massless Goldstone bosons and an exponential spectrum of massive hadrons. A third order transition is possible only if repulsive hadron interactions via the excluded volume effect are included.

Massive holographic QCD in the Veneziano limit

“…This article is part of an ongoing program [30,[37][38][39][40][41][42] for studying the properties of the V-QCD models, and in more general the structure of QCD in the Veneziano limit. There are several possible future directions to explore.…”

“…The sectors are fully backreacted in JHEP07(2015)033 the Veneziano limit. The structure of V-QCD at finite temperature and chemical potential has been studied in [37][38][39][40]. Two-point correlators and bound state masses were analyzed in [41,42].…”

“…In fact, the pressure of the model is still exactly zero in the TG phase, because our approach does not capture the contributions corresponding to loops of pions (as well as mesons with higher masses) in this phase. Including these contributions in the model would affect the critical temperature, and potentially even alter the order of the transition [40].…”

Improved Holographic QCD and the Quark--Gluon Plasma

“…Then V f 0 , w and κ are new potentials (in addition to V in (6)) that, in the bottom-up approximation should be fixed by phenomenological requirements as in the previous sections. The theory is further developed in the subsequent works in [46,48,49,51,52,53,54,55]. One typically also makes a simplifying assumption and takes κ(λ, T ) and w(λ, T ) independent of T .…”

Holography and the conformal window in the Veneziano limit

“…The glue and flavor sectors are fully backreacted in the Veneziano limit. The structure of V-QCD at finite temperature and chemical potential [13][14][15][16] as well as the two-point correlators and bound state masses [17][18][19] have also been analyzed.…”