Crying and Irritable Child

Magnetic-field dependence of the entanglement entropy of one-dimensional spin systems in quantum phase transitions induced by a quench

“…Indeed this expression corresponds to the geometric entropy for a conformal field theory derived by Holzhey, Larsen and Wilczek [2]. It has been shown in some earlier papers [3,4] that the central charge in conformal field theory corresponds to the Berry phase factor acquired by a spin state when it evolves in a closed path. The entanglement entropy of a pure state can be reduced to the measure of entanglement of formation in a mixed state given by concurrence [5].…”

“…It has been shown in earlier papers [3,4] that the central charge in conformal field theory is related to the Berry phase factor φ, the phase being e i2π φ which is acquired by a spin state when it evolves in a closed path. It may be pointed out that the measure of entanglement given by concurrence of nearest neighbor spins in a mixed state is equivalent to the entanglement entropy in a pure state [5].…”