Entanglement entropy in ’t Hooft model

Abstract

We use the replica trick approach to calculate, in the large-$N$ limit, the entanglement $c$-function in two-dimensional quantum chromodynamics with the gauge group $U(N)$ and quark in the fundamental representation ('t Hooft model). We show explicitly that the result is equal to a sum (with certain numerical coefficients) of entanglement $c$-functions of free massive scalars, which represent mesons in the spectrum of the 't Hooft model. Interestingly, each meson contributes as a pointlike particle. We provide an explanation for why this is the case.