A new catalog of photometric redshifts in the Hubble Deep Field

Using the newly available infrared images of the Hubble Deep Field in the J, H, and K bands and an optimal photometric method, we have refined a technique to estimate the redshifts of 1067 galaxies. A detailed comparison of our results with the spectroscopic redshifts in those cases where the latter are available shows that this technique gives very good results for bright enough objects (AB(8140) < 26.0). From a study of the distribution of residuals (Dz(rms)/(1+z) ~ 0.1 at all redshifts) we conclude that the observed errors are mainly due to cosmic variance. This very important result allows for the assessment of errors in quantities to be directly or indirectly measured from the catalog. We present some of the statistical properties of the ensemble of galaxies in the catalog, and finish by presenting a list of bright high-redshift (z ~ 5) candidates extracted from our catalog, together with recent spectroscopic redshift determinations confirming that two of them are at z=5.34 and z=5.60.Comment: 28 pages, 12PS+4JPEG figures, aaspp style. Accepted for publication in The Astrophysical Journal. The catalog, together with a clickable map of the HDF, Tables 4 and 5 (HTML, LaTeX or ASCII format), and the figures, are available at http://bat.phys.unsw.edu.au/~fsoto/hdfcat.htm

The Nuclear Yukawa Model on a Lattice

We present the results of the quantum field theory approach to nuclear Yukawa model obtained by standard lattice techniques. We have considered the simplest case of two identical fermions interacting via a scalar meson exchange. Calculations have been performed using Wilson fermions in the quenched approximation. We found the existence of a critical coupling constant above which the model cannot be numerically solved. The range of the accessible coupling constants is below the threshold value for producing two-body bound states. Two-body scattering lengths have been obtained and compared to the non relativistic results.Comment: 15 page

Ghost-gluon coupling, power corrections and ΛMS‾\Lambda_{\overline {\rm MS}} from twisted-mass lattice QCD at Nf=2

We present results concerning the non-perturbative evaluation of the ghost-gluon running QCD coupling constant from $N_f=2$ twisted-mass lattice calculations. A novel method for calibrating the lattice spacing, independent of the string tension and hadron spectrum is presented with results in agreement with previous estimates. The value of $\Lambda_{\overline{MS}}$ is computed from the running of the QCD coupling only after extrapolating to zero dynamical quark mass and after removing a non-perturbative OPE contribution that is assumed to be dominated by the dimension-two \VEV{A^2} gluon condensate. The effect due to the dynamical quark mass in the determination of \Lams is discussed.Comment: 33 pages, 6 fig

Generalized Casimir forces in non-equilibrium systems

In the present work we propose a method to determine fluctuation induced forces in non equilibrium systems. These forces are the analogue of the well known Casimir forces, which were originally introduced in Quantum Field theory and later extended to the area of Critical Phenomena. The procedure starts from the observation that many non equilibrium systems exhibit long-range correlations and the associated structure factors diverge in the long wavelength limit. The introduction of external bodies into such systems in general modifies the spectrum of these fluctuations and leads to the appearance of a net force between these bodies. The mechanism is illustrated by means of a simple example: a reaction diffusion equation with random noises.Comment: Submitted to Europhysics Letters. 7 pages, 2 figure

NMR Evidence for Antiferromagnetic Transition in the Single-Component Molecular Conductor, [Au(tmdt)_{2}] at 110 K

We present the results of a ^{1}H NMR study of the single-component molecular conductor, [Au(tmdt)_{2}]. A steep increase in the NMR line width and a peak formation of the nuclear spin-lattice relaxation rate, 1/T_{1}, were observed at around 110 K. This behavior provides clear and microscopic evidences for a magnetic phase transition at considerably high temperature among organic conductors. The observed variation in 1/T_{1} with respect to temperature indicates the highly correlated nature of the metallic phase.Comment: 5pages, 6figures to be published in J. Phys. Soc. Jp

Quantum phases of a qutrit

We consider various approaches to treat the phases of a qutrit. Although it is possible to represent qutrits in a convenient geometrical manner by resorting to a generalization of the Poincare sphere, we argue that the appropriate way of dealing with this problem is through phase operators associated with the algebra su(3). The rather unusual properties of these phases are caused by the small dimension of the system and are explored in detail. We also examine the positive operator-valued measures that can describe the qutrit phase properties.Comment: 6 page

Tackling the undeclared economy in the European Union: an evaluation of the tax morale approach

To evaluate a new approach towards tackling the undeclared economy which views participants as social actors rather than rational economic actors, this paper reports evidence from 27,563 face-to-face interviews conducted across the European Union during 2013. Multilevel logistic regression analysis reveals a strong association between participation in undeclared work and the level of tax morale. Finding that higher tax morale (and thus a lower propensity to engage in undeclared work) is strongly correlated with greater levels of state intervention but also with individual-level characteristics such as gender, age, education and employment status, the paper concludes not only by confirming a political economy approach and refuting modernization and neo-liberal explanations and remedies, but also by revealing for the first time the importance of solutions not so far considered, including improving educational attainment, older citizens mentoring for younger people, and improving women’s participation in the labour force

Seismic source mechanisms of tremor recorded on Arenal volcano, Costa Rica, retrieved by waveform inversion

International audienceMoment tensor inversions of volcanic tremor are synthetically tested and subsequently applied to a dataset recorded on Arenal volcano in 2005. We selected 15 harmonic tremor events showing an emergent but very clear onset with a fundamental frequency range of 0.8-1.5 Hz. These events constitute an excellent opportunity to broaden our knowledge of tremor generation models. The inversions were performed for a common source location, the position of which was retrieved through the evaluation of the joint probability density function of the misfit values obtained by the moment tensor inversion of all the events and all predefined source locations (grid search). Events are located beneath the summit crater, in a shallow position. The inversion procedure was tested through the use of synthetic tremor, generated using full wavefield numerical simulations. The maximum amplitude decomposition method is used to analyse the solutions of the synthetic tests. The results highlight the stability of the moment tensor solution when the whole length of the signal is used in the inversion procedure. Hence the whole length of the tremor is utilised to retrieve the source mechanism generating the 15 tremor events. A sliding window is utilised to investigate the time variability of our solution. A crack dipping 20° to the North-Northeast is reconcilable with all 15 tremor events. This mechanism is found to be constant for the entire length of each tremor and for different events

Superconductivity of Quasi-Two-Dimensional Tight-Binding Electrons in a Strong Magnetic Field

We have investigated the transition temperature $T_{\rm c}(H)$ of superconductiv ity in quasi-two-dimensional (Q2D) tight-binding electrons in a strong magnetic field. When the magnetic field is parallel to 2D conducting plane, $T_{\rm c}(H)$ of the Q2D superconductor is shown to increase in an oscillatory manner as the magnetic field becomes large and to reach $T_{\rm c}(0)$ in a strong magnetic f ield limit for the spin-triplet superconductor. We consider the cases of on-site and nearest sites attractive interaction, and calculate the magnetic field depe ndences of the transition temperature for various types of symmetry. The first o rder transition from $p_y$-wave to $p_x$-wave is shown to occur at $H\sim 35$T w hen the magnetic field is parallel to the $y$ direction, which will be observed in a triplet superconductor, Sr$_2$RuO$_4$.Comment: 13pages,6figure

Exercise-based interventions to enhance long-term sustainability of physical activity in older adults: a systematic review and meta-analysis of randomized clinical trials

Older adults; Physical activity; AdherenceAdultos mayores; Actividad física; AdherenciaAdults majors; Activitat física; AdherènciaExercise is a form of physical activity (PA). PA is an important marker of health and quality of life in older adults. The purpose of this study was to conduct a systematic review of the literature to assess the effect of exercise-based interventions on an at least six-month follow up PA measure, and to describe the specific strategies implemented during the intervention to strengthen the sustainability of PA in community-dwelling 65+ year-old adults. We registered and conducted a systematic review and meta-analysis (PROSPERO: CRD42017070892) of randomized clinical trials (RCT). We searched three electronic databases during January 2018 to identify RCT assessing any type of exercise-based intervention. Studies had to report a pre-, post-, and at least 6-month post-intervention follow-up. To be included, at least one PA outcome had to be assessed. The effect of exercise-based interventions was assessed compared to active (e.g., a low-intensity type of exercise, such as stretching or toning activities) and non-active (e.g., usual care) control interventions at several time points. Secondary analyses were conducted, restricted to studies that reported specific strategies to enhance the sustainability of PA. The intervention effect was measured on self-reported and objective measures of time spent in PA, by means of standardized mean differences. Standardized mean differences of PA level were pooled. Pooled estimates of effect were computed with the DerSimonian–Laird method, applying a random effects model. The risk of bias was also assessed. We included 12 studies, comparing 18 exercise intervention groups to four active and nine non-active control groups. Nine studies reported specific strategies to enhance the long-term sustainability of PA. The strategies were mostly related to the self-efficacy, self-control, and behavior capability principles based on the social cognitive theory. Exercise interventions compared to active control showed inconclusive and heterogeneous results. When compared to non-active control, exercise interventions improved PA time at the six-months follow up (standardized mean difference (SMD) 0.30; 95%CI 0.15 to 0.44; four studies; 724 participants; I2 0%), but not at the one- or two-years follow-ups. No data were available on the mid- and long-term effect of adding strategies to enhance the sustainability of PA. Exercise interventions have small clinical benefits on PA levels in community-dwelling older adults, with a decline in the observed improvement after six months of the intervention cessation.The present study was funded by United States Department of Health & Human Services National Institutes of Health (NIH), USA, and NIH National Institute on Aging (NIA), USA, (K24 AG057728)