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Baity-Jesi M.,Complutense University of Madrid | Baity-Jesi M.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | Baity-Jesi M.,University of Rome La Sapienza | Fernandez L.A.,Complutense University of Madrid | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We characterize the phase diagram of anisotropic Heisenberg spin glasses, finding both the spin and the chiral glass transition. We remark on the presence of strong finite-size effects in the chiral sector. On the spin glass sector, we find that the universality class is that of Ising spin glasses. Our data are compatible with a unique phase transition for the chiral and spin glass sector. We focus on keeping finite-size effects under control, and we stress that they are important to understand experiments. Thanks to large GPU clusters we have been able to thermalize cubic lattices with up to 643 spins, over a vast range of temperatures (hence, of relaxation times). © 2014 American Physical Society.


Fytas N.G.,Complutense University of Madrid | Fytas N.G.,Coventry University | Martin-Mayor V.,Complutense University of Madrid | Martin-Mayor V.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi
Physical Review Letters | Year: 2013

We solve a long-standing puzzle in statistical mechanics of disordered systems. By performing a high-statistics simulation of the D=3 random-field Ising model at zero temperature for different shapes of the random-field distribution, we show that the model is ruled by a single universality class. We compute the complete set of critical exponents for this class, including the correction-to-scaling exponent, and we show, to high numerical accuracy, that scaling is described by two independent exponents. Discrepancies with previous works are explained in terms of strong scaling corrections. © 2013 American Physical Society.


Fernandez L.A.,Complutense University of Madrid | Fernandez L.A.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | Gordillo-Guerrero A.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | Gordillo-Guerrero A.,University of Extremadura | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We present a microcanonical Monte Carlo simulation of the site-diluted Potts model in three dimensions with eight internal states, partly carried out on the citizen supercomputer Ibercivis. Upon dilution, the pure model's first-order transition becomes of the second order at a tricritical point. We compute accurately the critical exponents at the tricritical point. As expected from the Cardy-Jacobsen conjecture, they are compatible with their random field Ising model counterpart. The conclusion is further reinforced by comparison with older data for the Potts model with four states. © 2012 American Physical Society.


Fytas N.G.,Coventry University | Martin-Mayor V.,Complutense University of Madrid | Martin-Mayor V.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2016

It was recently shown [Phys. Rev. Lett. 110, 227201 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.227201] that the critical behavior of the random-field Ising model in three dimensions is ruled by a single universality class. This conclusion was reached only after a proper taming of the large scaling corrections of the model by applying a combined approach of various techniques, coming from the zero- and positive-temperature toolboxes of statistical physics. In the present contribution we provide a detailed description of this combined scheme, explaining in detail the zero-temperature numerical scheme and developing the generalized fluctuation-dissipation formula that allowed us to compute connected and disconnected correlation functions of the model. We discuss the error evolution of our method and we illustrate the infinite limit-size extrapolation of several observables within phenomenological renormalization. We present an extension of the quotients method that allows us to obtain estimates of the critical exponent α of the specific heat of the model via the scaling of the bond energy and we discuss the self-averaging properties of the system and the algorithmic aspects of the maximum-flow algorithm used. © 2016 American Physical Society.


Fernandez L.A.,Complutense University of Madrid | Fernandez L.A.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | Martin-Mayor V.,Complutense University of Madrid | Martin-Mayor V.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | And 4 more authors.
EPL | Year: 2013

Temperature chaos has often been reported in the literature as a rare-event-driven phenomenon. However, this fact has always been ignored in the data analysis, thus erasing the signal of the chaotic behavior (still rare in the sizes achieved) and leading to an overall picture of a weak and gradual phenomenon. On the contrary, our analysis relies on a large-deviations functional that allows to discuss the size dependences. In addition, we had at our disposal unprecedentedly large configurations equilibrated at low temperatures, thanks to the Janus computer. According to our results, when temperature chaos occurs its effects are strong and can be felt even at short distances. © Copyright EPLA, 2013.


Gordillo-Guerrero A.,University of Extremadura | Gordillo-Guerrero A.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | Kenna R.,Coventry University | Ruiz-Lorenzo J.J.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | Ruiz-Lorenzo J.J.,University of Extremadura
Journal of Statistical Mechanics: Theory and Experiment | Year: 2011

We use a high-precision Monte Carlo simulation to determine the universal specific-heat amplitude ratio A+/A- in the three-dimensional Ising model via the impact angle of complex temperature zeros. We also measure the correlation-length critical exponent ν from finite-size scaling and the specific-heat exponent α through hyperscaling. Extrapolations to the thermodynamic limit yield = 59.2(1.0)°, A +/A- = 0.56(3), ν = 0.630 48(32) and α = 0.1086(10). These results are compatible with some previous estimates from a variety of sources and rule out recently conjectured exact values. © IOP Publishing Ltd.


Parisi G.,University of Rome La Sapienza | Parisi G.,CNR Institute of Neuroscience | Seoane B.,University of Rome La Sapienza | Seoane B.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

We show in numerical simulations that a system of two coupled replicas of a binary mixture of hard spheres undergoes a phase transition in equilibrium at a density slightly smaller than the glass transition density for an unreplicated system. This result is in agreement with the theories that predict that such a transition is a precursor of the standard ideal glass transition. The critical properties are compatible with those of an Ising system. The relations of this approach to the conventional approach based on configurational entropy are briefly discussed. © 2014 American Physical Society.


Gordillo-Guerrero A.,University of Extremadura | Gordillo-Guerrero A.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | Kenna R.,Coventry University | Ruiz-Lorenzo J.J.,Institute Biocomputacion And Fisica Of Sistemas Complejos Bifi | Ruiz-Lorenzo J.J.,University of Extremadura
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

We report on extensive numerical simulations of the three-dimensional Heisenberg model and its analysis through finite-size scaling of Lee-Yang zeros. Besides the critical regime, we also investigate scaling in the ferromagnetic phase. We show that, in this case of broken symmetry, the corrections to scaling contain information on the Goldstone modes. We present a comprehensive Lee-Yang analysis, including the density of zeros, and confirm recent numerical estimates for critical exponents. © 2013 American Physical Society.

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