Inverse anisotropic catalysis in holographic QCD

Abstract

We investigate the effects of anisotropy on the chiral condensate in a holographic model of QCD with a fully backreacted quark sector at vanishing chemical potential. The high temperature deconfined phase is therefore a neutral and anisotropic plasma showing different pressure gradients along different spatial directions, similar to the state produced in noncentral heavy-ion collisions. We find that the chiral transition occurs at a lower temperature in the presence of anisotropy. Equivalently, we find that anisotropy acts destructively on the chiral condensate near the transition temperature. These are precisely the same footprints as the "inverse magnetic catalysis" i.e. the destruction of the condensate with increasing magnetic field observed earlier on the lattice, in effective field theory models and in holography. Based on our findings we suggest, in accordance with the conjecture of [1], that the cause for the inverse magnetic catalysis may be the anisotropy caused by the presence of the magnetic field instead of the charge dynamics created by it. We conclude that the weakening of the chiral condensate due to anisotropy is more general than that due to a magnetic field and we coin the former "inverse anisotropic catalysis". Finally, we observe that any amount of anisotropy changes the IR physics substantially: the geometry is AdS 4ˆR up to small corrections, confinement is present only up to a certain scale, and the particles acquire finite widths.

Holographic anisotropic background with confinement-deconfinement phase transition

“…As to further development, we suppose to study modifications of the model [61] to include light quarks following [112], incorporate the chiral phase transition [113], and also perform the numerical calculations in full anisotropic case to incorporate the magnetic field, as has been done in [114].…”

Cool baryon and quark matter in holographic QCD

“…Therefore the instability which we observe here is indeed undesirable for QCD. For a more detailed discussion of confinement in a similar geometry, we refer to [76]. Note that thermodynamic properties like the equation of state are much less affected by this change in geometry, as they do not probe the deep IR.…”

Holographic spontaneous anisotropy

“…This in principle could lead to the observation of stars more compact than the ones allowed by isotropic matter, see, e.g., [3,4]. Strongly coupled anisotropic phases have been studied using holography in a variety of setups, including axionic/dilatonic sources [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], electric [21][22][23] and magnetic fields [24][25][26][27][28][29][30][31][32][33] or both [34][35][36][37][38], and p-wave superfluids [39][40][41][42][43][44]. Strongly coupled holographic matter has also been studied in the context of compact stars [45][46][47][48][49][...…”