Quantum quench in the attractive regime of the sine-Gordon model

Understand

We study the dynamics of the sine-Gordon model after a quantum quench into the attractive regime, where the spectrum consists of solitons, antisolitons and breathers.

• In particular, we analyse the time-dependent expectation value of the vertex operator, $\exp\left({\rm i}\beta\Phi/2\right)$, starting from an initial state in the "squeezed state form" corresponding to integrable boundary conditions.
• Using an expansion in terms of exact form factors, we compute analytically the leading contributions to this expectation value at late times.
• We show that form factors containing breathers only contribute to the late-time dynamics if the initial state exhibits zero-momentum breather states.