Stationary entropies after a quench from excited states in the Ising chain
1 MTA-BME Momentum Statistical Field Theory Research Group - 1111 Budapest, Budafoki út 8, Hungary
2 Dipartimento di Fisica dell'Università di Pisa and INFN - 56127 Pisa, Italy
Received: 3 July 2014
Accepted: 22 July 2014
We consider the asymptotic state after a sudden quench of the magnetic field in the transverse field quantum Ising chain starting from excited states of the pre-quench Hamiltonian. We compute the thermodynamic entropies of the generalised Gibbs and the diagonal ensembles and we find that the generalised Gibbs entropy is always twice the diagonal one. We show that particular care should be taken in extracting the thermodynamic limit since different averages of equivalent microstates give different results for the entropies.
PACS: 03.67.Mn – Entanglement measures, witnesses, and other characterizations / 05.70.Ln – Nonequilibrium and irreversible thermodynamics / 75.10.Pq – Spin chain models
© EPLA, 2014