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Pontecorvo, Italy

Crecchi F.,University of Chicago | Crecchi F.,Normal School of Pisa | Vicari E.,DellUniversity Pisa
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We investigate the effects of a trapping space-dependent potential on the low-temperature quasi-long-range order phase of two-dimensional particle systems with a relevant U(1) symmetry, such as quantum atomic gases. We characterize the universal features of the trap-size dependence using scaling arguments. The resulting scenario is supported by numerical Monte Carlo simulations of a classical two-dimensional XY model with a space-dependent hopping parameter, the inhomogeneity of which is analogous to that arising from the trapping potential in experiments of atomic gases. © 2011 American Physical Society.

Strumia A.,CERN | Strumia A.,DellUniversity Pisa | Strumia A.,National Institute of Nuclear Physics, Italy
Journal of High Energy Physics | Year: 2010

We reconsider thermal production of axinos in the early universe, adding: a) missed terms in the axino interaction; b) production via gluon decays kinematically allowed by thermal masses; c) a precise modeling of reheating. We find an axino abunance a few times larger than previous computations. © SISSA 2010.

D'Elia M.,DellUniversity Pisa | Negro F.,DellUniversity Genoa
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We study the phase diagram of non-Abelian pure gauge theories in the presence of a topological θ term. The dependence of the deconfinement temperature on θ is determined on the lattice both by analytic continuation and by reweighting, obtaining consistent results. The general structure of the diagram is discussed on the basis of large-N considerations and of the possible analogies and dualities existing with the phase diagram of QCD in the presence of an imaginary baryon chemical potential. © 2013 American Physical Society.

Fagotti M.,DellUniversity Pisa | Fagotti M.,University of Oxford
EPL | Year: 2012

We study the entanglement of two disjoint blocks in spin- 1/2 chains obtained by merging solvable models, such as XX and quantum Ising models. We focus on the universal quantities that can be extracted from the Rényi entropies S α. The most important information is encoded in some functions denoted by F α. We compute F 2and we show that F α ?1 and Fv.N., corresponding to the von Neumann entropy, can be negative, in contrast to what observed in all models examined so far. An exact relation between the entanglement of disjoint subsystems in the XX model and that in a chain embodying two quantum Ising models is a by-product of our investigations. © 2012 Europhysics Letters Association.

Collura M.,DellUniversity Pisa | Karevski D.,CNRS Jean Lamour Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We consider a quantum quench in a noninteracting fermionic one-dimensional field theory. The system of size L is initially prepared into two halves L ([-L/2,0]) and R ([0,L/2]), each of them thermalized at two different temperatures TL and TR, respectively. At a given time, the two halves are joined together by a local coupling and the whole system is left to evolve unitarily. For an infinitely extended system (L→), we show that the time evolution of the particle and energy densities is well described via a hydrodynamic approach which allows us to evaluate the correspondent stationary currents. We show, in such a case, that the two-point correlation functions are deduced, at large times, from a simple nonequilibrium steady state. Otherwise, whenever the boundary conditions are retained (in a properly defined thermodynamic limit), any current is suppressed at large times, and the stationary state is described by a generalized Gibbs ensemble, which is diagonal and depends only on the post-quench mode occupation. © 2014 American Physical Society.

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