Generalized Clausius inequalities and entanglement production in holographic two-dimensional CFTs

TL;DR

This paper uses the quantum null energy condition to establish bounds on entropy production in 2D holographic CFTs during quenches, and analyzes entanglement growth and information scrambling.

Contribution

It develops an algebraic method for determining HRT surfaces in arbitrary geometries and refines bounds on entropy production using QNEC in holographic CFTs.

Findings

Bounds on entropy production are derived using QNEC.

Entanglement entropy growth depends only on energy density change.

Large entangling lengths exhibit entanglement tsunami phenomena.

Abstract

Utilizing quantum information theory, it has been shown that irreversible entropy production is bounded from both below and above in physical processes. Both these bounds are positive and generalize the Clausius inequality. Such bounds are, however, obtained from distance measures in the space of states, which are hard to define and compute in quantum field theories. We show that the quantum null energy condition (QNEC) can be utilized to obtain both lower and upper bounds on irreversible entropy production for quenches leading to transitions between thermal states carrying uniform momentum density in two dimensional holographic conformal field theories. We achieve this by refining earlier methods and developing an algebraic procedure for determining HRT surfaces in arbitrary Ba\~nados-Vaidya geometries which are dual to quenches involving transitions between general quantum equilibrium states (e.g. thermal states) where the QNEC is saturated. We also discuss results for the growth and thermalization of entanglement entropy for arbitrary initial and final temperatures and momentum densities. The rate of quadratic growth of entanglement just after the quench depends only on the change in the energy density and is independent of the entangling length. For sufficiently large entangling lengths, the entanglement tsunami phenomenon can be established. Finally, we study recovery of the initial state from the evolving entanglement entropy and argue that the Renyi entropies should give us a refined understanding of scrambling of quantum information.