5,685 research outputs found
Ferruccio Bertini, Inusitata verba. Studi di lessicografia latina. Raccolti in occasione del suo settantesimo compleanno da Paolo GATTI e Caterina Mordeglia. Trente, Università degli Studi, 2011
No full textRochette Bruno. Ferruccio Bertini, Inusitata verba. Studi di lessicografia latina. Raccolti in occasione del suo settantesimo compleanno da Paolo GATTI e Caterina Mordeglia. Trente, Università degli Studi, 2011. In: L'antiquité classique, Tome 81, 2012. pp. 302-303
Low-temperature transport in out-of-equilibrium XXZ chains
Full text linkWe study the low-temperature transport properties of out-of equilibrium XXZ spin-1/2 chains. We consider the protocol where two semiinfinite chains are prepared in two thermal states at small but different temperatures and suddenly joined together. We focus on the qualitative and quantitative features of the profiles of local observables, which at large times t and distances x from the junction become functions of the ratio ζ = x/t. By means of the generalized hydrodynamic equations, we analyse the rich phenomenology arising by considering different regimes of the phase diagram. In the gapped phases, variations of the profiles are found to be exponentially small in the temperatures, but described by non-trivial functions of ζ. We provide analytical formulae for the latter, which give accurate results also for small but finite temperatures. In the gapless regime, we show how the three-step conformal predictions for the profiles of energy density and energy current are naturally recovered from the hydrodynamic equations. Moreover, we also recover the recent non-linear Luttinger liquid predictions for low-temperature transport: universal peaks of width ∆ζ ∝ T emerge at the edges of the light cone in the profiles of generic observables. Such peaks are described by the same function of ζ for all local observables
Scrambling in random unitary circuits: Exact results
Full text linkWe study the scrambling of quantum information in local random unitary circuits by focusing on the tripartite information proposed by Hosur et al. We provide exact results for the averaged Rényi-2 tripartite information in two cases: (i) the local gates are Haar random and (ii) the local gates are dual-unitary and randomly sampled from a single-site Haar-invariant measure. We show that the latter case defines a one-parameter family of circuits, and prove that for a “maximally chaotic” subset of this family quantum information is scrambled faster than in the Haar-random case. Our approach is based on a standard mapping onto an averaged folded tensor network, that can be studied by means of appropriate recurrence relations. By means of the same method, we also revisit the computation of out-of-time-ordered correlation functions, rederiving known formulas for Haar-random unitary circuits, and presenting an exact result for maximally chaotic random dual-unitary gates
Quantum quenches in the sinh-Gordon model: steady state and one-point correlation functions
No full textWe consider quantum quenches to the sinh-Gordon integrable quantum field theory from a particular class of initial states. Our analysis includes the case of mass and interaction quenches starting from a non-interacting theory. By means of the recently developed quench action method, we fully characterize the stationary state reached at long times after the quench in terms of the corresponding rapidity distribution. We also provide exact results for the expectation values of arbitrary vertex operators in the post-quench stationary state by proposing a formula based on the analogy with the standard thermodynamic Bethe ansatz. Finally, we comment on the behavior of the post-quench stationary state under the mapping between the sinh-Gordon field theory and the one-dimensional Lieb-Liniger model
Universal broadening of the light cone in low-temperature transport
Full text linkWe consider the low-temperature transport properties of critical one-dimensional systems that can be described, at equilibrium, by a Luttinger liquid. We focus on the prototypical setting where two semi-infinite chains are prepared in two thermal states at small but different temperatures and suddenly joined together. At large distances x and times t, conformal field theory characterizes the energy transport in terms of a single light cone spreading at the sound velocity v. Energy density and current take different constant values inside the light cone, on its left, and on its right, resulting in a three-step form of the corresponding profiles as a function of ζ=x/t. Here, using a nonlinear Luttinger liquid description, we show that for generic observables this picture is spoiled as soon as a nonlinearity in the spectrum is present. In correspondence of the transition points x/t=±v, a novel universal region emerges at infinite times, whose width is proportional to the temperatures on the two sides. In this region, expectation values have a different temperature dependence and show smooth peaks as a function of ζ. We explicitly compute the universal function describing such peaks. In the specific case of interacting integrable models, our predictions are analytically recovered by the generalized hydrodynamic approach
Corrigendum to âResponse to: Mitochondrial neuropathy affects peripheral and cranial nerves and is primary or secondary or bothâ [Neuromuscular Disorders 26/8 (2016) 549](S0960896616302899)(10.1016/j.nmd.2016.06.007)
No full textThe authors regret that the order of the first and last names was listed incorrectly in the above letter. The correct order for the authors' names is: Michelangelo Mancuso, Daniele Orsucci, Corrado Angelini, Enrico Bertini, Claudio Bruno, Valerio Carelli, Giacomo P. Comi, Massimiliano Filosto, Costanza Lamperti, Maurizio Moggio, Tiziana Mongini, Isabella Moroni, Paola Tonin, Antonio Toscano, Gabriele Siciliano, on behalf of the Nation-wide Italian Collaborative Network of Mitochondrial Diseases. Moreover, as this was a letter, only the affiliation of the corresponding author (M. Mancuso) was given. The corresponding author's address is not the affiliation for all other authors except for Daniele Orsucci and Gabriele Siciliano who share the same affiliation: Department of Clinical and Experimental Medicine, Neurological Institute, University of Pisa, Pisa, Italy. The authors would like to apologise for any inconvenience caused
Quantum quench in the infinitely repulsive Hubbard model: The stationary state
No full textWe use the quench action approach to study the non-equilibrium dynamics after a quantum quench in the Hubbard model in the limit of infinite interaction. We identify a variety of low-entangled initial states for which we can directly compute the overlaps with the Hamiltonian's eigenstates. For these initial states, we analytically find the rapidity distributions of the stationary state characterising the expectation values of all local observables. Some of the initial states considered are not reflection symmetric and lead to non-symmetric rapidity distributions. To study such cases, we have to introduce a generalised form for the reduced entropy which measures the entropy restricted to states with non-zero overlap. The initial states considered are of direct experimental realisability and also represent ideal candidates for studying non-equilibrium dynamics in the Hubbard model for finite interactions
Entanglement and diagonal entropies after a quench with no pair structure
Full text linkA typical working condition in the study of quantum quenches is that the initial state produces a distribution of quasiparticle excitations with an opposite-momentum-pair structure. In this work we investigate the dynamical and stationary properties of the entanglement entropy after a quench from initial states which do not have such structure: instead of pairs of excitations they generate -plets of correlated excitations with > 2. Our study is carried out focusing on a system of non-interacting fermions on the lattice. We study the time evolution of the entanglement entropy showing that the standard semiclassical formula is not applicable. We propose a suitable generalisation which correctly describes the entanglement entropy evolution and perfectly matches numerical data. We finally consider the relation between the thermodynamic entropy of the stationary state and the diagonal entropy, showing that when there is no pair structure their ratio depends on the details of the initial state and lies generically between 1/2 and 1
Solution of the BEC to BCS Quench in One Dimension
Full text linkA gas of interacting fermions confined in a quasi one-dimensional geometry
shows a BEC to BCS crossover upon slowly driving its coupling constant through
a confinement-induced resonance. On one side of the crossover the fermions form
tightly-bound bosonic molecules behaving as a repulsive Bose gas, while on the
other they form Cooper pairs, whose size is much larger than the average
inter-particle distance. Here we consider the situation arising when the
coupling constant is varied suddenly from the BEC to the BCS value. Namely, we
study a BEC-to-BCS quench. By exploiting a suitable continuum limit of recently
discovered solvable quenches in the Hubbard model, we show that the local
stationary state reached at large times after the quench can be determined
exactly by means of the Quench Action approach. We provide an
experimentally-accessible characterisation of the stationary state by computing
local pair correlation function as well as the quasi-particle distribution
functions. We find that the steady state is increasingly dominated by two
particle spin singlet bound states for stronger interaction strength but that
bound state formation is inhibited at larger BEC density. The bound state
rapidity distribution displays quartic power law decay suggesting a violation
of Tan's contact relations.Comment: 5 pages, 2 figure
Exact solution for the quench dynamics of a nested integrable system
Full text linkIntegrable models provide an exact description for a wide variety of
physical phenomena. For example nested integrable systems contain
different species of interacting particles with a rich phenomenology in
their collective behavior, which is the origin of the unconventional
phenomenon of spin-charge separation. So far, however, most of the
theoretical work in the study of non-equilibrium dynamics of integrable
systems has focussed on models with an elementary (i.e. not nested)
Bethe ansatz. In this work we explicitly investigate quantum quenches in
nested integrable systems, by generalizing the application of the quench
action approach. Specifically, we consider the spin-1 Lai-Sutherland
model, described, in the thermodynamic limit, by the theory of two
different species of Bethe-ansatz particles, each one forming an
infinite number of bound states. We focus on the situation where the
quench dynamics starts from a simple matrix product state for which the
overlaps with the eigenstates of the Hamiltonian are known. We fully
characterize the post-quench steady state and perform several
consistency checks for the validity of our results. Finally, we provide
predictions for the propagation of entanglement and mutual information
after the quench, which can be used as signature of the quasi-particle
content of the model
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