Self-consistent Keldysh approach to quenches in weakly interacting Bose-Hubbard model

We present a non-equilibrium Green's functional approach to study the dynamics following a quench in weakly interacting Bose Hubbard model (BHM). The technique is based on the self-consistent solution of a set of equations which represents a particular case of the most general set of Hedin's equations for the interacting single-particle Green's function. We use the ladder approximation as a skeleton diagram for the two-particle scattering amplitude useful, through the self-energy in the Dyson equation, for finding the interacting single-particle Green's function. This scheme is then implemented numerically by a parallelized code. We exploit this approach to study the correlation propagation after a quench in the interaction parameter, for one (1D) and two (2D) dimensions. In particular, we show how our approach is able to recover the crossover from ballistic to diffusive regime by increasing the boson-boson interaction. Finally we also discuss the role of a thermal initial state on the dynamics both for 1D and 2D Bose Hubbard models, finding that surprisingly at high temperature a ballistic evolution is restored.Comment: 13 figure

Protecting entanglement via the quantum Zeno effect

We study the exact entanglement dynamics of two atoms in a lossy resonator. Besides discussing the steady-state entanglement, we show that in the strong coupling regime the system-reservoir correlations induce entanglement revivals and oscillations and propose a strategy to fight against the deterioration of the entanglement using the quantum Zeno effect.Comment: 4 pages, 3 figure

Quantum Otto cycle with inner friction: finite-time and disorder effects

The concept of inner friction, by which a quantum heat engine is unable to follow adiabatically its strokes and thus dissipates useful energy, is illustrated in an exact physical model where the working substance consists of an ensemble of misaligned spins interacting with a magnetic field and performing the Otto cycle. The effect of this static disorder under a finite-time cycle gives a new perspective of the concept of inner friction under realistic settings. We investigate the efficiency and power of this engine and relate its performance to the amount of friction from misalignment and to the temperature difference between heat baths. Finally we propose an alternative experimental implementation of the cycle where the spin is encoded in the degree of polarization of photons.Comment: Published version in the Focus Issue on "Quantum Thermodynamics

Structural change of vortex patterns in anisotropic Bose-Einstein condensates

We study the changes in the spatial distribution of vortices in a rotating Bose-Einstein condensate due to an increasing anisotropy of the trapping potential. Once the rotational symmetry is broken, we find that the vortex system undergoes a rich variety of structural changes, including the formation of zig-zag and linear configurations. These spatial re-arrangements are well signaled by the change in the behavior of the vortex-pattern eigenmodes against the anisotropy parameter. The existence of such structural changes opens up possibilities for the coherent exploitation of effective many-body systems based on vortex patterns.Comment: 5 pages, 4 figure

Critical assessment of two-qubit post-Markovian master equations

A post-Markovian master equation has been recently proposed as a tool to describe the evolution of a system coupled to a memory-keeping environment [A. Shabani and D. A. Lidar, Phys. Rev. A 71, 020101 (R) (2005)]. For a single qubit affected by appropriately chosen environmental conditions, the corresponding dynamics is always legitimate and physical. Here we extend such situation to the case of two qubits, only one of which experiences the environmental effects. We show how, despite the innocence of such an extension, the introduction of the second qubit should be done cum grano salis to avoid consequences such as the breaking of the positivity of the associated dynamical map. This hints at the necessity of using care when adopting phenomenologically derived models for evolutions occurring outside the Markovian framework.Comment: 7 pages, 1 figure, RevTeX4. Close to published versio

First record of Helobdella hyalina (Hirudinea; Glossiphoniidae) in the mantle cavity of Planorbidae from lentic environments in a Buenos Aires province, Argentina

Biomphalaria peregrina (D’Orbigny, 1835) and Drepanotrema kermatoides (D’Orbigny, 1835) were first reported as hosts of Helobdella hyalina Ringuelet, 1942. Both are important species from the Río de La Plata river basin in Argentina. They are associated with macrophytes of lentic or semilentic environments. They are more frequently observed in semipermanent low-depth environments with vegetation and abundant organic matter (Bonetto et al., 1990).\n(Párrafo extraído del texto a modo de resumen)</i

Alcohol consumption in young adults: the role of multisensory imagery.

Accepted 19.11.2013Little is known about the subjective experience of alcohol desire and craving in young people. Descriptions of alcohol urges continue to be extensively used in the everyday lexicon of young, non-dependent drinkers. Elaborated Intrusion (EI) Theory contends that imagery is central to craving and desires, and predicts that alcohol-related imagery will be associated with greater frequency and amount of drinking. This study involved 1,535 age stratified 18- 25 year olds who completed an alcohol–related survey that included the Imagery scale of the Alcohol Craving Experience (ACE) questionnaire. Imagery items predicted 12-16% of the variance in concurrent alcohol consumption. Higher total Imagery subscale scores were linearly associated with greater drinking frequency and lower self-efficacy for moderate drinking. Interference with alcohol imagery may have promise as a preventive or early intervention target in young people

Homogeneity of Interspecific Hybrids Between Saccharomyces cerevisiae and Saccharomyces uvarum by Phenotypic and Transcriptional Analysis

Oenological traits, such as temperature profile and production of certain metabolites, were tested for four interspecifc hybrids obtained by"spore to spore" crossing between Saccharomyces cerevisiae and Saccharomyces uvarum strains and uniformity of their inheritance was found. PCR/RFLP analysis of ITS regions was carried out to confirm the hybrid nature of the strains. They showed an additive profile with five bands of the respective 325, 230, 170 and 125 bp. Finally gene expression study was performed by comparative DNA macroarray analysis of the hybrids and the preliminary results showed that the global gene expression patterns of hybrids are remarkably similar to one another. In conclusion, the data obtained by two different approaches, such as metabolic and transcriptomic strategies, suggest a large degree of homogeneity among interspecific hybrids between S. cerevisiae and S. uvarum. Moreover, the uniformity of F1 hybrids advises that the oenological trait inheritance mechanism is highly constant and reproducible