Off-diagonal Flavour Susceptibilities from AdS/CFT

TL;DR

This paper investigates off-diagonal flavour susceptibilities in a strongly coupled supersymmetric plasma using AdS/CFT, revealing finite values at infinite coupling and cautioning against naive extrapolations to QCD.

Contribution

It provides the first gravity dual calculation of off-diagonal susceptibilities at strong coupling, showing their finite limit and independence from meson states.

Findings

Off-diagonal susceptibility is 1/N-suppressed and finite at strong coupling.

The susceptibility's form is independent of meson bound states.

Results suggest caution in interpreting lattice QCD susceptibilities.

Abstract

We study flavour susceptibilities in the ${\cal N}=4$ SU(N) super Yang-Mills plasma coupled to two quark flavours at strong coupling and large $N$ by means of its gravity dual. The off-diagonal susceptibility is 1/N-suppressed and we compute it as a one-loop effect on the gravity side. Contrary to naive extrapolation from perturbative results, it attains a finite value in the infinite-coupling limit. Moreover, its parametric form is independent of whether or not meson bound states exist in the plasma. We conclude that caution must be exercised when drawing conclusions about the QCD plasma from lattice calculations of quark susceptibilities.