Egorov property in perturbed cat map

We study the time evolution of the quantum-classical correspondence (QCC) for the well known model of quantised perturbed cat maps on the torus in the very specific regime of semi-classically small perturbations. The quality of the QCC is measured by the overlap of classical phase-space density and corresponding Wigner function of the quantum system called quantum-classical fidelity (QCF). In the analysed regime the QCF strongly deviates from the known general behaviour in particular it decays faster then exponential. Here we study and explain the observed behavior of the QCF and the apparent violation of the QCC principle.Comment: 12 pages, 7 figure

Deterministic spin models with a glassy phase transition

We consider the infinite-range deterministic spin models with Hamiltonian $H=\sum_{i,j=1}^N J_{i,j}\sigma_i\sigma_j$, where $J$ is the quantization of a chaotic map of the torus. The mean field (TAP) equations are derived by summing the high temperature expansion. They predict a glassy phase transition at the critical temperature $T\sim 0.8$.Comment: 8 pages, no figures, RevTex forma

Pairing, crystallization and string correlations of mass-imbalanced atomic mixtures in one-dimensional optical lattices

We numerically determine the very rich phase diagram of mass-imbalanced binary mixtures of hardcore bosons (or equivalently -- fermions, or hardcore-Bose/Fermi mixtures) loaded in one-dimensional optical lattices. Focusing on commensurate fillings away from half filling, we find a strong asymmetry between attractive and repulsive interactions. Attraction is found to always lead to pairing, associated with a spin gap, and to pair crystallization for very strong mass imbalance. In the repulsive case the two atomic components remain instead fully gapless over a large parameter range; only a very strong mass imbalance leads to the opening of a spin gap. The spin-gap phase is the precursor of a crystalline phase occurring for an even stronger mass imbalance. The fundamental asymmetry of the phase diagram is at odds with recent theoretical predictions, and can be tested directly via time-of-flight experiments on trapped cold atoms.Comment: 4 pages, 4 figures + Supplementary Materia

Scaling of excitations in dimerized and frustrated spin-1/2 chains

We study the finite-size behavior of the low-lying excitations of spin-1/2 Heisenberg chains with dimerization and next-to-nearest neighbors interaction, J_2. The numerical analysis, performed using density-matrix renormalization group, confirms previous exact diagonalization results, and shows that, for different values of the dimerization parameter \delta, the elementary triplet and singlet excitations present a clear scaling behavior in a wide range of \ell=L/\xi (where L is the length of the chain and \xi is the correlation length). At J_2=J_2c, where no logarithmic corrections are present, we compare the numerical results with finite-size predictions for the sine-Gordon model obtained using Luscher's theory. For small \delta we find a very good agreement for \ell > 4 or 7 depending on the excitation considered.Comment: 4 pages, 4 eps figures, RevTeX 4 class, same version as in PR

Relative entropy via non-sequential recursive pair substitutions

The entropy of an ergodic source is the limit of properly rescaled 1-block entropies of sources obtained applying successive non-sequential recursive pairs substitutions (see P. Grassberger 2002 ArXiv:physics/0207023 and D. Benedetto, E. Caglioti and D. Gabrielli 2006 Jour. Stat. Mech. Theo. Exp. 09 doi:10.1088/1742.-5468/2006/09/P09011). In this paper we prove that the cross entropy and the Kullback-Leibler divergence can be obtained in a similar way.Comment: 13 pages , 2 figure

Ab initio analysis of the x-ray absorption spectrum of the myoglobin-carbon monoxide complex: Structure and vibrations

We present a comparison between Fe K-edge x-ray absorption spectra of carbonmonoxy-myoglobin and its simulation based on density-functional theory determination of the structure and vibrations and spectral simulation with multiple-scattering theory. An excellent comparison is obtained for the main part of the molecular structure without any structural fitting parameters. The geometry of the CO ligand is reliably determined using a synergic approach to data analysis. The methodology underlying this approach is expected to be especially useful in similar situations in which high-resolution data for structure and vibrations are available.Comment: 13 pages, 3 figure

Quantum-classical correspondence on compact phase space

We propose to study the $L^2$-norm distance between classical and quantum phase space distributions, where for the latter we choose the Wigner function, as a global phase space indicator of quantum-classical correspondence. For example, this quantity should provide a key to understand the correspondence between quantum and classical Loschmidt echoes. We concentrate on fully chaotic systems with compact (finite) classical phase space. By means of numerical simulations and heuristic arguments we find that the quantum-classical fidelity stays at one up to Ehrenfest-type time scale, which is proportional to the logarithm of effective Planck constant, and decays exponentially with a maximal classical Lyapunov exponent, after that time.Comment: 26 pages. 9 figures (31 .epz files), submitted to Nonlinearit

Adherence in HIV-positive patients treated with single-tablet regimens and multi-pill regimens: findings from the COMPACT study

The use of Combination AntiRetroviral Therapy (cART) has decreased the morbidity and mortality of patients infected with HIV. However, adherence to cART remains crucial to prevent virological failure and disease progression. The aim of this study was to assess adherence to treatment among patients treated with Single Tablet Regimen (STR) or with multi-pill regimens based on Protease Inhibitors (PI), Non-Nucleoside Reverse-Transcriptase Inhibitors (NNRTI), or raltegravir (RAL). An observational retrospective cohort analysis based on administrative and clinical databases was conducted at the National Institute for Infectious Diseases (Rome, Italy). HIV-positive patients treated with a cART between Jan 1st, 2008–Dec 31st, 2010 were included. Patients were followed-up for one year since the first prescription during the inclusion period or up to death or switch of at least one drug of the regimen. Adherence and selective non-adherence (days without backbone or 3rd drug) were calculated using pharmacy refill compliance [1]. cART regimens were classified based on number of daily pills (STR vs multi-pill regimen) and on type of third drug. Viral Load (VL) and CD4 cell counts at the end of the follow-up were evaluated. A total of 1,604 patients were analyzed, 70.0% male, age 45.0±8.7, 14.3% newly treated. Patients on STR were 159 (9.9%), PI 878 (54.7%), NNRTI 523 (32.6%), RAL 44 (2.7%). Presence of at least one AIDS-defining conditions (according to Centers for Disease Control classification) was 30% in the STR group, 34% PI, 26% NNRTI, 34% RAL (p=n.s.). Adherence was 80.4±14.7% for STR, 71.8±21.8% PI, 77.1±20.3% NNRTI, 74.0±22.4% RAL. Selective non-adherence was 5.5% (18 days) PI, 2.8% (8 days) NNRTI, 12.5% (43 days) RAL (Figure 1). At the end of the follow-up, VL/CD4 values were available among 709 patients (44%); CD4 count >500 cell/mm3 was observed among 61% of patients on STR, 44% PI, 48% NNRTI, 42% RAL and VL < 50 copies/ml was observed among 96% of patients on STR, 78% PI, 88% NNRTI, 87% RAL. Interruptions in cART refill remain a relevant problem across all cART regimens. Patients on STR displayed a higher adherence rate compared to multi-pill regimes (PI, NNRTI, and RAL), primarily due to lack of selective non-adherence. Patients on STR experienced also higher rates of VL < 50 and CD4 > 500. The use of an STR regimen appears an effective therapeutic option to avoid selective non-adherence and, consequently, to prevent virological failure and disease progression

Quantum response of weakly chaotic systems

Chaotic systems, that have a small Lyapunov exponent, do not obey the common random matrix theory predictions within a wide "weak quantum chaos" regime. This leads to a novel prediction for the rate of heating for cold atoms in optical billiards with vibrating walls. The Hamiltonian matrix of the driven system does not look like one from a Gaussian ensemble, but rather it is very sparse. This sparsity can be characterized by parameters $s$ and $g$ that reflect the percentage of large elements, and their connectivity respectively. For $g$ we use a resistor network calculation that has direct relation to the semi-linear response characteristics of the system.Comment: 7 pages, 5 figures, expanded improved versio

Crystal properties of eigenstates for quantum cat maps

Using the Bargmann-Husimi representation of quantum mechanics on a torus phase space, we study analytically eigenstates of quantized cat maps. The linearity of these maps implies a close relationship between classically invariant sublattices on the one hand, and the patterns (or `constellations') of Husimi zeros of certain quantum eigenstates on the other hand. For these states, the zero patterns are crystals on the torus. As a consequence, we can compute explicit families of eigenstates for which the zero patterns become uniformly distributed on the torus phase space in the limit $\hbar\to 0$. This result constitutes a first rigorous example of semi-classical equidistribution for Husimi zeros of eigenstates in quantized one-dimensional chaotic systems.Comment: 43 pages, LaTeX, including 7 eps figures Some amendments were made in order to clarify the text, mainly in the 4 first sections. Figures are unchanged. To be published in: Nonlinearit