title: Parity effects in the scaling of block entanglement in gapless spin chains.
abstract: We consider the Rényi alpha entropies for Luttinger liquids (LL). For large block lengths l, these are known to grow like lnl. We show that there are subleading terms that oscillate with frequency 2k{F} (the Fermi wave number of the LL) and exhibit a universal power-law decay with l. The new critical exponent is equal to K/(2alpha), where K is the LL parameter. We present numerical results for the anisotropic XXZ model and the full analytic solution for the free fermion (XX) point.
authors.affiliation: Dipartimento di Fisica, dell'Università di Pisa and INFN, 56127 Pisa, Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Calabrese
authors.forename: Massimo
authors.initials: M
authors.lastname: Campostrini
authors.forename: Fabian
authors.initials: F
authors.lastname: Essler
authors.forename: Bernard
authors.initials: B
authors.lastname: Nienhuis