Nonlinear boundary dynamics and chiral symmetry in holographic QCD

Abstract

In a hard-wall model of holographic QCD, we find that nonlinear boundary dynamics are required in order to maintain the correct pattern of explicit and spontaneous chiral symmetry breaking beyond leading order in the pion fields. With the help of a field redefinition, we relate the requisite nonlinear boundary conditions to a standard Sturm-Liouville system. Observables insensitive to the chiral limit receive only small corrections in the improved description, and classical calculations in the hard-wall model remain surprisingly accurate.

Enhancement of chiral symmetry breaking from the pion condensation at finite isospin chemical potential in a holographic QCD model

“…Our results show that the phase transition is of the second order, which is consistent with the one obtained in the Oðp 2 Þ chiral Lagrangian [3], as well as the one in the holographic QCD model [27]. It is remarkable that the chiral condensate defined byσ ≡ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi hσi 2 þ hπ a i 2 p is almost constant in the small μ I region, while it grows with μ I in the large μ I region.…”

“…In this sense, an analysis by models may give some clues to understand the phase structure and the relevant phenomenon in the mid μ I region. Actually, many analyses were done by using the Nambu-Jona-Lasinio model [8][9][10][11][12][13][14][15], the random matrix model [16], the strong coupling lattice analysis [17], the Ginzburg-Landau approach [18], the hadron resonance gas model [19], and the holographic QCD models [20][21][22][23][24][25][26][27][28][29][30][31].…”

Meson effective mass in the isospin medium in hard-wall AdS/QCD model

“…Indeed, the modification of the boundary condition at the infrared boundary is known from Refs. [37,52]. In [52], the axial-vector field interacting with the condensate field gets a contribution in mass and this results in a modification in the boundary condition at z I R .…”

“…The AdS/QCD idea was extended to the finite temperature case in [17][18][19][20][21][22][23][24][25][26] and a great number of works were devoted to a holographic description of the quark-gluon plasma and dense nuclear matter [27][28][29]. In the framework of holographic QCD the studies in the dense nucleon and isospin mediums turned out a e-mail: sh.mamedov62@gmail.com to be as effective in a top-down approach [30][31][32][33] as in a bottom-up one [34][35][36][37][38][39].…”

“…It should be noticed that the IR boundary shift in the hard-wall model already is known from Refs. [37,52], where the authors deal with the bulk interaction of the fields, which contribute to the boundary meson mass.…”