Exact mesoscopic correlation functions of the pairing model

We study the static correlation functions of the Richardson pairing model (also known as the reduced or discrete-state BCS model) in the canonical ensemble. Making use of the Algebraic Bethe Ansatz formalism, we obtain exact expressions which are easily evaluated numerically for any value of the pairing strength up to large numbers of particles. We provide explicit results at half-filling and extensively discuss their finite-size scaling behavior.Comment: 15 Pages, 12 figure

Time evolution of local observables after quenching to an integrable model

We consider quantum quenches in integrable models. We argue that the behaviour of local observables at late times after the quench is given by their expectation values with respect to a single representative Hamiltonian eigenstate. This can be viewed as a generalization of the eigenstate thermalization hypothesis to quantum integrable models. We present a method for constructing this representative state by means of a generalized Thermodynamic Bethe Ansatz (GTBA). Going further, we introduce a framework for calculating the time dependence of local observables as they evolve towards their stationary values. As an explicit example we consider quantum quenches in the transverse-field Ising chain and show that previously derived results are recovered efficiently within our framework.Comment: 7 page

Tracking the effects of interactions on spinons in gapless Heisenberg chains

We consider the effects of interactions on spinon excitations in Heisenberg spin-1/2 chains. We compute the exact two-spinon part of the longitudinal structure factor of the infinite chain in zero field for all values of anisotropy in the gapless antiferromagnetic regime, via an exact algebraic approach. Our results allow us to quantitatively describe the behavior of these fundamental excitations throughout the observable continuum, for cases ranging from free to fully coupled chains, thereby explicitly mapping the effects of "turning on the interactions" in a strongly correlated system

Interaction quenches in the 1D Bose gas

The non-equilibrium dynamics of integrable systems are special: there is substantial evidence that after a quantum quench they do not thermalize but their asymptotic steady state can be described by a Generalized Gibbs Ensemble (GGE). Most of the studies on the GGE so far have focused on models that can be mapped to quadratic systems while analytic treatment in non-quadratic systems remained elusive. We obtain results on interaction quenches in a non-quadratic continuum system, the 1D Bose gas described by the integrable Lieb-Liniger model. We compute local correlators for a non-interacting initial state and arbitrary final interactions as well as two-point functions for quenches to the Tonks-Girardeau regime. We show that in the long time limit integrability leads to significant deviations from the predictions of the grand canonical ensemble.Comment: Supersedes arXiv:1204.3889. 4+ pages + Supplementary Materia

Drag Force and Hess-Fairbank Effect in the One-Dimensional Bose Gas

Different aspects of superfluidity in one dimension (1D) are discussed in this paper. It is shown that the Hess-Fairbank effect takes place in 1D at zero temperature. In particular, the rotational inertia of an interacting 1D Bose gas in a finite ring is zero. Nevertheless, our results indicate that the frictionless motion of impurities depends sensitively on the strength of interactions in the gas. In general, this is possible only in a limit of weak interactions. We obtain the phase diagram of frictionless motion for the gas immersed into a moving shallow optical lattice. In this case the drag force, a quantitative measure of superfluidity, can be zero at specific values of lattice velocity and the gas density even for strong interactions.В работе обсуждаются различные аспекты сверхтекучести в одномерном бозе-газе. Показано, что в одномерном случае при нулевой температуре проявляется эффект Хесса-Фэрбэнка. В частности, момент инерции одномерного неидеального бозе-газа, заключенного в кольцо, равен нулю. Несмотря на это, полученные результаты показывают, что отсутствие трения при движении примеси в газе определяется силой взаимодействия между бозонами. В общем случае это возможно только в пределе слабого взаимодействия. Мы получили фазовую диаграмму свободного от трения движения газа в оптической решетке. В этом случае сила сопротивления, являющаяся количественной мерой сверхтекучести, может отсутствовать даже для сильного взаимодействия при некоторых значениях скорости решетки и средней газовой плотности

Drag Force and Hess-Fairbank Effect in the One-Dimensional Bose Gas

Different aspects of superfluidity in one dimension (1D) are discussed in this paper. It is shown that the Hess-Fairbank effect takes place in 1D at zero temperature. In particular, the rotational inertia of an interacting 1D Bose gas in a finite ring is zero. Nevertheless, our results indicate that the frictionless motion of impurities depends sensitively on the strength of interactions in the gas. In general, this is possible only in a limit of weak interactions. We obtain the phase diagram of frictionless motion for the gas immersed into a moving shallow optical lattice. In this case the drag force, a quantitative measure of superfluidity, can be zero at specific values of lattice velocity and the gas density even for strong interactions.В работе обсуждаются различные аспекты сверхтекучести в одномерном бозе-газе. Показано, что в одномерном случае при нулевой температуре проявляется эффект Хесса-Фэрбэнка. В частности, момент инерции одномерного неидеального бозе-газа, заключенного в кольцо, равен нулю. Несмотря на это, полученные результаты показывают, что отсутствие трения при движении примеси в газе определяется силой взаимодействия между бозонами. В общем случае это возможно только в пределе слабого взаимодействия. Мы получили фазовую диаграмму свободного от трения движения газа в оптической решетке. В этом случае сила сопротивления, являющаяся количественной мерой сверхтекучести, может отсутствовать даже для сильного взаимодействия при некоторых значениях скорости решетки и средней газовой плотности

Efficacy and Tolerance of Anti–Tumor Necrosis Factor α Agents in Cutaneous Sarcoidosis

International audienceEvidence for the long-term efficacy and safety of anti-tumor necrosis factor α agents (anti-TNF) in treating cutaneous sarcoidosis is lacking

First-line rituximab combined with short-term prednisone versus prednisone alone for the treatment of pemphigus (Ritux 3): a prospective, multicentre, parallel-group, open-label randomised trial.

IF 44.002International audienceBackground High doses of corticosteroids are considered the standard treatment for pemphigus. Because long-term corticosteroid treatment can cause severe and even life-threatening side-effects in patients with this disease, we assessed whether first-line use of rituximab as adjuvant therapy could improve the proportion of patients achieving complete remission off-therapy, compared with corticosteroid treatment alone, while decreasing treatment side-effects of corticosteroids.Methods We did a prospective, multicentre, parallel-group, open-label, randomised trial in 25 dermatology hospital departments in France (Ritux 3). Eligible participants were patients with newly diagnosed pemphigus aged 18-80 years being treated for the first time (not at the time of a relapse). We randomly assigned participants (1: 1) to receive either oral prednisone alone, 1.0 or 1.5 mg/kg per day tapered over 12 or 18 months (prednisone alone group), or 1000 mg of intravenous rituximab on days 0 and 14, and 500 mg at months 12 and 18, combined with a short-term prednisone regimen, 0.5 or 1.0 mg/kg per day tapered over 3 or 6 months (rituximab plus short-term prednisone group). Follow-up was for 3 years (study visits were scheduled weekly during the first month of the study, then monthly until month 24, then an additional visit at month 36). Treatment was assigned through central computer-generated randomisation, with stratification according to disease-severity (severe or moderate, based on Harman's criteria). The primary endpoint was the proportion of patients who achieved complete remission off-therapy at month 24 (intention-to-treat analysis). This study is registered with ClinicalTrials.gov, number NCT00784589.Findings Between May 10, 2010, and Dec 7, 2012, we enrolled 91 patients and randomly assigned 90 to treatment (90 were analysed; 1 patient withdrew consent before the random assignment). At month 24, 41 (89%) of 46 patients assigned to rituximab plus short-term prednisone were in complete remission off-therapy versus 15 (34%) of 44 assigned to prednisone alone (absolute difference 55 percentage points, 95% CI 38.4-71.7; p<0.0001. This difference corresponded to a relative risk of success of 2.61 (95% CI 1.71-3.99, p<0.0001), corresponding to 1.82 patients (95% CI 1.39-2.60) who would need to be treated with rituximab plus prednisone (rather than prednisone alone) for one additional success. No patient died during the study. More severe adverse events of grade 3-4 were reported in the prednisone-alone group (53 events in 29 patients; mean 1.20 [SD 1.25]) than in the rituximab plus prednisone group (27 events in 16 patients; mean 0.59 [1.15]; p=0.0021). The most common of these events in both groups were diabetes and endocrine disorder (11 [21%] with prednisone alone vs six [22%] with rituximab plus prednisone), myopathy (ten [19%] vs three [11%]), and bone disorders (five [9%] vs five [19%]).Interpretation Data from our trial suggest that first-line use of rituximab plus short-term prednisone for patients with pemphigus is more effective than using prednisone alone, with fewer adverse events