Inhomogeneous conformal field theory out of equilibrium

TL;DR

This paper develops an exact analytical framework for studying non-equilibrium heat and charge transport in inhomogeneous 1+1D conformal field theories with position-dependent velocities, revealing diffusion and generalized Wiedemann-Franz law.

Contribution

It introduces a method to compute exact non-equilibrium dynamics in inhomogeneous CFTs with smooth profiles, extending understanding of transport and correlations in such systems.

Findings

Exact time evolution of densities and currents derived

Correlation functions for energy-momentum tensor and U(1) current obtained

Explicit expressions for thermal and electrical conductivities provided

Abstract

We study the non-equilibrium dynamics of conformal field theory (CFT) in 1+1 dimensions with a smooth position-dependent velocity $v(x)$ explicitly breaking translation invariance. Such inhomogeneous CFT is argued to effectively describe 1+1-dimensional quantum many-body systems with certain inhomogeneities varying on mesoscopic scales. Both heat and charge transport are studied, where, for concreteness, we suppose that our CFT has a conserved U$(1)$ current. Based on projective unitary representations of diffeomorphisms and smooth maps in Minkowskian CFT, we obtain a recipe for computing the exact non-equilibrium dynamics in inhomogeneous CFT when evolving from initial states defined by smooth inverse-temperature and chemical-potential profiles $\beta(x)$ and $\mu(x)$. Using this recipe, the following exact analytical results are obtained: (i) the full time evolution of densities and currents for heat and charge transport, (ii) correlation functions for components of the energy-momentum tensor and the U$(1)$ current as well as for any primary field, and (iii) the thermal and electrical conductivities. The latter are computed by direct dynamical considerations and alternatively using a Green-Kubo formula. Both give the same explicit expressions for the conductivities, which reveal how inhomogeneous dynamics opens up the possibility for diffusion as well as implies a generalization of the Wiedemann-Franz law to finite times within CFT.