Quantum Local Quench, AdS/BCFT and Yo-Yo String

TL;DR

This paper introduces a holographic model for local quenches in 1+1D CFTs using AdS/BCFT, where a tensionless Yo-Yo string in the bulk captures the entanglement dynamics after joining two semi-infinite theories.

Contribution

It presents a novel holographic description of local quenches via a dynamical folded string, linking boundary CFT processes to bulk string evolution and entanglement entropy calculations.

Findings

The model reproduces known field theory entanglement entropy results.

The Yo-Yo string dynamics deform Ryu-Takayanagi curves consistently.

Holographic entanglement entropy matches field theory predictions.

Abstract

We propose a holographic model for local quench in 1+1 dimensional Conformal Field Theory (CFT). The local quench is produced by joining two identical CFT's on semi-infinite lines. When these theories have a zero boundary entropy, we use the AdS/Boundary CFT proposal to describe this process in terms of bulk physics. Boundaries of the original CFT's are extended in AdS as dynamical surfaces. In our holographic picture these surfaces detach from the boundary and form a closed folded string which can propagate in the bulk. The dynamics of this string is governed by the tensionless Yo-Yo string solution and its subsequent evolution determines the time dependence after quench. We use this model to calculate holographic Entanglement Entropy (EE) of an interval as a function of time. We propose how the falling string deforms Ryu-Takayanagi's curves. Using the deformed curves we calculate EE and find complete agreement with field theory results.