Domain growth within the backbone of the three-dimensional ±J\pm J Edwards-Anderson spin glass

The goal of this work is to show that a ferromagnetic-like domain growth process takes place within the backbone of the three-dimensional $\pm J$ Edwards-Anderson (EA) spin glass model. To sustain this affirmation we study the heterogeneities displayed in the out-of-equilibrium dynamics of the model. We show that both correlation function and mean flipping time distribution present features that have a direct relation with spatial heterogeneities, and that they can be characterized by the backbone structure. In order to gain intuition we analyze the pure ferromagnetic Ising model, where we show the presence of dynamical heterogeneities in the mean flipping time distribution that are directly associated to ferromagnetic growing domains. We extend a method devised to detect domain walls in the Ising model to carry out a similar analysis in the three-dimensional EA spin glass model. This allows us to show that there exists a domain growth process within the backbone of this model.Comment: 10 pages, 10 figure

Signature of the Ground-State Topology in the Low-Temperature Dynamics of Spin Glasses

We numerically address the issue of how the ground state topology is reflected in the finite temperature dynamics of the $\pm J$ Edwards-Anderson spin glass model. In this system a careful study of the ground state configurations allows to classify spins into two sets: solidary and non-solidary spins. We show that these sets quantitatively account for the dynamical heterogeneities found in the mean flipping time distribution at finite low temperatures. The results highlight the relevance of taking into account the ground state topology in the analysis of the finite temperature dynamics of spin glasses.Comment: 4 pages, 4 figures, content change

Dynamical heterogeneities as fingerprints of a backbone structure in Potts models

We investigate slow non-equilibrium dynamical processes in two-dimensional $q$--state Potts model with both ferromagnetic and $\pm J$ couplings. Dynamical properties are characterized by means of the mean-flipping time distribution. This quantity is known for clearly unveiling dynamical heterogeneities. Using a two-times protocol we characterize the different time scales observed and relate them to growth processes occurring in the system. In particular we target the possible relation between the different time scales and the spatial heterogeneities originated in the ground state topology, which are associated to the presence of a backbone structure. We perform numerical simulations using an approach based on graphics processing units (GPUs) which permits to reach large system sizes. We present evidence supporting both the idea of a growing process in the preasymptotic regime of the glassy phases and the existence of a backbone structure behind this processes.Comment: 9 pages, 7 figures, Accepted for publication in PR

A influência da diferenciação das relações líder-membro no comprometimento com a unidade de trabalho: o papel mediador do clima de apoio

We investigated whether the influence of LMX differentiation (the extent to which the quality of the leader-member relationships within a work unit varies) on work unit commitment is mediated by support climate. We tested this mediated relationship in a sample composed of 30 health care units. The results obtained showed that LMX differentiation measured at Time 1 was negatively related to work unit support climate measured one year later (Time 2), which in turn was positively related to work unit commitment measured at Time 2. The negative indirect effect of LMX differentiation on work unit commitment through support climate was statistically significant. Our study contributes to having a better understanding of the role of LMX differentiation in work unit functioning.Investigámos se a influência da diferenciação de LMX (o quanto a qualidade das relações de líder-membro dentro de uma unidade de trabalho varia) no comprometimento com a unidade de trabalho é mediada pelo clima de apoio. Testámos essa relação mediada em uma amostra composta por 30 unidades de saúde. Os resultados obtidos mostraram que a diferenciação da LMX medida no Tempo 1 foi negativamente relacionada ao clima de suporte da unidade de trabalho medido um ano depois (Tempo 2), que por sua vez foi positivamente relacionado ao comprometimento com a unidade de trabalho medido no Tempo 2. O efeito indireto negativo da diferenciação da LMX no comprometimento com a unidade de trabalho por meio do clima de apoio foi estatisticamente significativo. O nosso estudo contribui para uma melhor compreensão do papel da diferenciação do LMX no funcionamento da unidade de trabalho

Critical behavior of repulsive linear kk-mers on triangular lattices

Monte Carlo (MC) simulations and finite-size scaling analysis have been carried out to study the critical behavior in a submonolayer two-dimensional gas of repulsive linear $k$-mers on a triangular lattice at coverage $k/(2k+1)$. A low-temperature ordered phase, characterized by a repetition of alternating files of adsorbed $k$-mers separated by $k+1$ adjacent empty sites, is separated from the disordered state by a order-disorder phase transition occurring at a finite critical temperature, $T_c$. The MC technique was combined with the recently reported Free Energy Minimization Criterion Approach (FEMCA), [F. Rom\'a et al., Phys. Rev. B, 68, 205407, (2003)], to predict the dependence of the critical temperature of the order-disorder transformation. The dependence on $k$ of the transition temperature, $T_c(k)$, observed in MC is in qualitative agreement with FEMCA. In addition, an accurate determination of the critical exponents has been obtained for adsorbate sizes ranging between $k=1$ and $k=3$. For $k>1$, the results reveal that the system does not belong to the universality class of the two-dimensional Potts model with $q=3$ ($k=1$, monomers). Based on symmetry concepts, we suggested that the behavior observed for $k=1, 2$ and 3 could be generalized to include larger particle sizes ($k \geq 2$).Comment: 17 pages, 13 figure

Quasi-chemical approximation for polyatomics: Statistical thermodynamics of adsorption

The statistical thermodynamics of interacting polyatomic adsorbates (k-mers) on homogeneous surfaces was developed on a generalization in the spirit of the lattice-gas model and the quasi-chemical approximation (QCA). The new theoretical framework is obtained by combining (i) the exact analytical expression for the partition function of non-interacting linear k-mers adsorbed in one dimension and its extension to higher dimensions, and (ii) a generalization of the classical QCA in which the adsorbate can occupy more than one adsorption site. The coverage and temperature dependence of the Helmholtz free energy, chemical potential, configurational entropy, configurational energy, isosteric heat of adsorption and specific heat are given. The formalism reproduces the classical QCA for monomers, leads to the exact statistical thermodynamics of interacting k-mers adsorbed in one dimension, and provides a close approximation for two-dimensional systems accounting multisite occupancy. Comparisons with analytical data from Bragg-Williams approximation (BWA) and Monte Carlo simulations are performed in order to test the validity of the theoretical model. The resulting thermodynamic description is significantly better than the BWA and still mathematically handable.Fil: Dávila, M.. Universidad Nacional de San Luis; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro | Universidad Nacional de Cuyo. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro; ArgentinaFil: Romá, Federico José. Universidad Nacional de San Luis; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; ArgentinaFil: Riccardo, Jose Luis. Universidad Nacional de San Luis; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; ArgentinaFil: Ramirez Pastor, Antonio Jose. Universidad Nacional de San Luis; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentin

Psychological climate, sickness absence and gender

We examined whether the relationship between psychological climate and sickness absence is moderated by gender. We expected that this relationship would be stronger among men than among women. We tested this general hypothesis using two samples of men and women nurses (made up of 114 and 189 subjects, respectively). The results obtained supported our expectation. The three climate facets considered (support, goals orientation and rules orientation) showed a significant relationship with sickness absence in the men sample, but not in the women sample. Clima psicológico, absentismo y género. Se investigó si la relación entre clima psicológico y absentismo por enfermedad está moderada por el género de los empleados. Se esperaba que la relación fuera más fuerte en hombres que en mujeres. Esta hipótesis general se puso a prueba utilizando dos muestras de enfermeros/as formadas por 114 varones y 189 mujeres. Los resultados obtenidos respaldaron nuestra hipótesis general. Las tres dimensiones de clima consideradas (apoyo, orientación hacia objetivos y orientación hacia reglas) mostraron una relación estadísticamente significativa con absentismo en la muestra de varones, pero no en la de mujeres

Surface phase transitions in one-dimensional channels arranged in a triangular cross-sectional structure: Theory and Monte Carlo simulations

Monte Carlo simulations and finite-size scaling analysis have been carried out to study the critical behavior in a submonolayer lattice-gas of interacting monomers adsorbed on one-dimensional channels arranged in a triangular cross-sectional structure. The model mimics a nanoporous environment, where each nanotube or unit cell is represented by a one-dimensional array. Two kinds of lateral interaction energies have been considered: $1)$ $w_L$, interaction energy between nearest-neighbor particles adsorbed along a single channel and $2)$ $w_T$, interaction energy between particles adsorbed across nearest-neighbor channels. For $w_L/w_T=0$ and $w_T > 0$, successive planes are uncorrelated, the system is equivalent to the triangular lattice and the well-known $(\sqrt{3} \times \sqrt{3})$ $[(\sqrt{3} \times \sqrt{3})^*]$ ordered phase is found at low temperatures and a coverage, $\theta$, of 1/3 $[2/3]$. In the more general case ($w_L/w_T \neq 0$ and $w_T > 0$), a competition between interactions along a single channel and a transverse coupling between sites in neighboring channels allows to evolve to a three-dimensional adsorbed layer. Consequently, the $(\sqrt{3} \times \sqrt{3})$ and $(\sqrt{3} \times \sqrt{3})^*$ structures "propagate" along the channels and new ordered phases appear in the adlayer. The Monte Carlo technique was combined with the recently reported Free Energy Minimization Criterion Approach (FEMCA), to predict the critical temperatures of the order-disorder transformation. The excellent qualitative agreement between simulated data and FEMCA results allow us to interpret the physical meaning of the mechanisms underlying the observed transitions.Comment: 24 pages, 6 figure