Record 16

Title: Thermodynamic glass transition in a spin glass without time-reversal symmetry

Author(s): Banos, RA; Cruz, A; Fernandez, LA; Gil-Narvion, JM; Gordillo-Guerrero, A; Guidetti, M; Iniguez, D; Maiorano, A; Marinari, E; Martin-Mayor, V; Monforte-Garcia, J; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ruiz-Lorenzo, JJ; Schifano, SF; Seoane, B; Tarancon, A; Tellez, P; Tripiccione, R; Yllanes, D

Source: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Volume: 109 Issue: 17 Pages: 6452-6456 DOI: 10.1073/PNAS.1203295109 Published: APR 24 2012

Abstract: Spin glasses are a longstanding model for the sluggish dynamics that appear at the glass transition. However, spin glasses differ from structural glasses in a crucial feature: they enjoy a time reversal symmetry. This symmetry can be broken by applying an external magnetic field, but embarrassingly little is known about the critical behavior of a spin glass in a field. In this context, the space dimension is crucial. Simulations are easier to interpret in a large number of dimensions, but one must work below the upper critical dimension (i.e., in d < 6) in order for results to have relevance for experiments. Here we show conclusive evidence for the presence of a phase transition in a four-dimensional spin glass in a field. Two ingredients were crucial for this achievement: massive numerical simulations were carried out on the Janus special-purpose computer, and a new and powerful finite-size scaling method.

ISSN: 0027-8424

Record 15

Title: Sample-to-sample fluctuations of the overlap distributions in the three-dimensional Edwards-Anderson spin glass

Author(s): Banos, RA; Cruz, A; Fernandez, LA; Gil-Narvion, JM; Gordillo-Guerrero, A; Guidetti, M; Iniguez, D; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Monforte-Garcia, J; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ricci-Tersenghi, F; Ruiz-Lorenzo, JJ; Schifano, SF; Seoane, B; Tarancon, A; Tripiccione, R; Yllanes, D

Source: PHYSICAL REVIEW B Volume: 84 Issue: 17Article Number: 174209 DOI: 10.1103/PhysRevB.84.174209 Published: NOV 28 2011

Abstract: We study the sample-to-sample fluctuations of the overlap probability densities from large-scale equilibrium simulations of the three-dimensional Edwards-Anderson spin glass below the critical temperature. Ultrametricity, stochastic stability, and overlap equivalence impose constraints on the moments of the overlap probability densities that can be tested against numerical data. We found small deviations from the Ghirlanda-Guerra predictions, which get smaller as system size increases. We also focus on the shape of the overlap distribution, comparing the numerical data to a mean-field-like prediction in which finite-size effects are taken into account by substituting delta functions with broad peaks.

ISSN:

Record 14

Author(s): Banos, RA ; Cruz, A; Fernandez, LA; Gil-Narvion, JM; Gordillo-Guerrero, A; Guidetti, M; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Monforte-Garcia, J; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ruiz-Lorenzo, JJ; Schifano, SF; Seoane, B; Tarancon, A; Tripiccione, R; Yllanes, D

Title: Static versus Dynamic Heterogeneities in the D=3 Edwards-Anderson-Ising Spin Glass

Source: PHYSICAL REVIEW LETTERS, 105 (17): Art. No. 177202 OCT 20 2010

Abstract: We numerically study the aging properties of the dynamical heterogeneities in the Ising spin glass. We find that a phase transition takes place during the aging process. Statics-dynamics correspondence implies that systems of finite size in equilibrium have static heterogeneities that obey finite-size scaling, thus signaling an analogous phase transition in the thermodynamical limit. We compute the critical exponents and the transition point in the equilibrium setting, and use them to show that aging in dynamic heterogeneities can be described by a finite-time scaling ansatz, with potential implications for experimental work.

ISSN: 0031-9007

Article Number: 177202

DOI: 10.1103/PhysRevLett.105.177202

Record 13

Author(s): Banos, RA; Cruz, A; Fernandez, LA; Gil-Narvion, JM; Gordillo-Guerrero, A; Guidetti, M; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Monforte-Garcia, J; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ruiz-Lorenzo, JJ; Schifano, SF; Seoane, B; Tarancon, A; Tripiccione, R; Yllanes, D

Title: Nature of the spin-glass phase at experimental length scales

Source: JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT: Art. No. P06026 JUN 2010

Abstract: We present a massive equilibrium simulation of the three-dimensional Ising spin glass at low temperatures. The Janus special-purpose computer has allowed us to equilibrate, using parallel tempering, L = 32 lattices down to T approximate to 0.64T(c). We demonstrate the relevance of equilibrium finite size simulations to understanding experimental non-equilibrium spin glasses in the thermodynamical limit by establishing a time-length dictionary. We conclude that non-equilibrium experiments performed on a timescale of 1 h can be matched with equilibrium results on L approximate to 110 lattices. A detailed investigation of the probability distribution functions of the spin and link overlap, as well as of their correlation functions, shows that Replica Symmetry Breaking is the appropriate theoretical framework for the physically relevant length scales. Besides, we improve over existing methodologies in ensuring equilibration in parallel tempering simulations.

ISSN: 1742-5468

Article Number: P06026

DOI: 10.1088/1742-5468/2010/06/P06026

Record 12

Author(s): Alvarez Banos, R.; Cruz, A; Fernandez, LA; Gordillo-Guerrero, A; Gil-Narvion, JM; Guidetti, M; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Monforte-Garcia, J; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ruiz-Lorenzo, JJ; Seoane, B; Schifano, SF; Tarancon, A; Tripiccione, R; Yllanes, D

Title: Critical behavior of three-dimensional disordered Potts models with many states

Source: JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT: Art. No. P05002 MAY 2010

Abstract: We study the 3D disordered Potts model with p = 5 and 6. Our numerical simulations (that severely slow down for increasing p) detect a very clear spin glass phase transition. We evaluate the critical exponents and the critical value of the temperature, and we use known results at lower p values to discuss how they evolve for increasing p. We do not find any sign of the presence of a transition to a ferromagnetic regime.

ISSN: 1742-5468

Article Number: P05002

DOI: 10.1088/1742-5468/2010/05/P05002

Record 11

Author(s): Belletti, F; Cotallo, M; Cruz, A; Fernandez, LA; Gordillo, A; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Munoz-Sudupe, A; Navarro, D; Perez-Gaviro, S; Rossi, M; Ruiz-Lorenzo, JJ; Schifano, SF; Sciretti, D; Tarancon, A; Tripiccione, R; Velasco, JL

Editor(s): Bischof, C; Bucker, C; Gibbon, P; Joubert, G; Lippert, T; Mohr, B; Peters, F

Title: IANUS: Scientific Computing on an FPGA-Based Architecture

Source: PARALLEL COMPUTING: ARCHITECTURES, ALGORITHNMS AND APPLICATIONS, 15: 553-560 2008

Book series title: Advances in Parallel Computing

Conference Title: International Parallel Computing Conference 2007

Conference Date: SEP 04-07, 2007

Conference Location: Aachen, FRANCE

Conference Host: RWTH Aachen Univ

Abstract: This paper describes the architecture and FPGA-based implementation of a massively parallel processing system (IANUS). carefully tailored to the computing requirements of a class of simulation problems relevant in statistical physics. we first discuss the system architecture in general and then focus on the configuration of the system for Monte Carlo simulation of spin-glass systems. This is the first large-scale application of the machine, on which IANUS achieves impressive performance. Our architecture uses large-scale on chip parallelism (similar or equal to 1000 computing cores on each processor) so it is a relevant example in the quickly expanding field of many-core architectures.

ISSN: 0927-5452

ISBN: 978-1-58603-796-3

Record 10

Author(s): Belletti, F; Cruz, A; Fernandez, LA; Gordillo-Guerrero, A; Guidetti, M; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Monforte, J; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ruiz-Lorenzo, JJ; Schifano, SF; Sciretti, D; Tarancon, A; Tripiccione, R; Yllanes, D

Title: An In-Depth View of the Microscopic Dynamics of Ising Spin Glasses at Fixed Temperature

Source: JOURNAL OF STATISTICAL PHYSICS, 135 (5-6): 1121-1158 Sp. Iss. SI JUN 2009

Abstract: Using the special-purpose computer Janus, we follow the nonequilibrium dynamics of the Ising spin glass in three dimensions for eleven orders of magnitude. The use of integral estimators for the coherence and correlation lengths allows us to study dynamic heterogeneities and the presence of a replicon mode and to obtain safe bounds on the Edwards-Anderson order parameter below the critical temperature. We obtain good agreement with experimental determinations of the temperature-dependent decay exponents for the thermoremanent magnetization. This magnitude is observed to scale with the much harder to measure coherence length, a potentially useful result for experimentalists. The exponents for energy relaxation display a linear dependence on temperature and reasonable extrapolations to the critical point. We conclude examining the time growth of the coherence length, with a comparison of critical and activated dynamics.

ISSN: 0022-4715

DOI: 10.1007/s10955-009-9727-z

Record 9

Author(s): Cruz, A; Fernandez, LA; Gordillo-Guerrero, A; Guidetti, M; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ruiz-Lorenzo, JJ; Schifano, SF; Sciretti, D; Tarancon, A; Tripiccione, R; Velasco, JL; Yllanes, D; Young, AP

Title: Spin glass phase in the four-state three-dimensional Potts model

Source: PHYSICAL REVIEW B, 79 (18): Art. No. 184408 MAY 2009

Abstract: We perform numerical simulations, including parallel tempering, a four-state Potts glass model with binary random quenched couplings using the JANUS application-oriented computer. We find and characterize a glassy transition, estimating the critical temperature and the value of the critical exponents. Nevertheless, the extrapolation to infinite volume is hampered by strong scaling corrections. We show that there is no ferromagnetic transition in a large temperature range around the glassy critical temperature. We also compare our results with those obtained recently on the "random permutation" Potts glass.

ISSN: 1098-0121

Article Number: 184408

DOI: 10.1103/PhysRevB.79.184408

Record 8

Author(s): Guidetti, M

Group Author(s): Janus Collaboration

Editor(s): Garrido, PL; Hurtado, PI; Marro, J

Title: Simulating Potts models on JANUS

Source: MODELING AND SIMULATION OF NEW MATERIALS, 1091: 225-227 2009

Book series title: AIP CONFERENCE PROCEEDINGS

Conference Title: 10th Granada Seminar

Conference Date: SEP 15-19, 2008

Conference Location: Granada, SPAIN

Conference Host: Univ Granada, Fac Ciencias

Abstract: We present results from a simulation of the four states Potts Glassy model. We provide evidence for a spin glass phase transition at beta approximate to 4. Also, we briefly describe JANUS, a massively parallel high performance FPGA-based computer that we have used for our simulation.

ISSN: 0094-243X

ISBN: 978-0-7354-0624-7

Record 7

Author(s): Belletti, F; Cruz, A; Fernandez, LA; Gordillo-Guerrero, A; Guidetti, M; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ruiz-Lorenzo, JJ; Schifano, SF; Sciretti, D; Tarancon, A; Tripiccione, R; Yllanes, D

Editor(s): Garrido, PL; Hurtado, PI; Marro, J

Title: Nonequilibrium spin glass dynamics with Janus

Source: MODELING AND SIMULATION OF NEW MATERIALS, 1091: 228-230 2009

Book series title: AIP CONFERENCE PROCEEDINGS

Conference Title: 10th Granada Seminar

Conference Date: SEP 15-19, 2008

Conference Location: Granada, SPAIN

Conference Host: Univ Granada, Fac Ciencias

Abstract: The out of equilibrium evolution for an Edwards-Anderson spin glass is followed for a tenth of a second, a long enough time to let us make safe predictions about the behaviour at experimental scales. This work has been made possible by Janus, an FPGA based special purpose computer. We have thoroughly studied the spin glass correlation functions and the growth of the coherence length for L = 80 lattices in 3D. Our main conclusion is that these spin glasses follow noncoarsening dynamics, at least up to the experimentally relevant time scales.

ISSN: 0094-243X

ISBN: 978-0-7354-0624-7

Record 6

Author(s): Belletti, F; Cotallo, M; Cruz, A; Fernandez, LA; Gordillo-Guerrero, A; Guidetti, M; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Rossi, M; Ruiz-Lorenzo, JJ; Saenz-Lorenzo, JF; Schifano, SF; Sciretti, D; Tarancon, A; Tripiccione, R; Velasco, JL; Yllanes, D; Zanier, G

Group Author(s): JANUS Collaboration

Title: Monte Carlo simulations for statistical physics: Janus

Source: NUOVO CIMENTO DELLA SOCIETA ITALIANA DI FISICA B-GENERAL PHYSICS RELATIVITY ASTRONOMY AND MATHEMATICAL PHYSICS AND METHODS, 123 (6-7): 972-974 JUN-JUL 2008

Conference Title: Italian Meeting on High Energy Physics

Conference Date: MAR 26-28, 2008

Conference Location: Bologna, ITALY

Abstract: Janus is an FPGA-based computer optimized for the simulation of spin glasses or similar condensed matter systems. Computing requirements in this area, are still riot met by available commercial systems, so all application-driven machine, boosting performance by approximately a factor 100x is in this case the only viable option to simulate large systems for a time window comparable with experiments.

ISSN: 1594-9982

DOI: 10.1393/ncb/i2008-10621-8

Record 5

Author(s): Belletti, F; Guidetti, M; Maiorano, A; Mantovani, F; Schifano, SF; Tripiccione, R; Cotallo, M; Perez-Gaviro, S; Sciretti, D; Velasco, JL; Cruz, A; Navarro, D; Tarancon, A; Fernandez, LA; Martin-Mayor, V; Munoz-Sudupe, A; Yllanes, D; Gordillo-Guerrero, A; Ruiz-Lorenzo, JJ; Marinari, E; Parisi, G; Rossi, M; Zanier, G

Title: Janus: An FPGA-Based System for High-Performance Scientific Computing

Source: COMPUTING IN SCIENCE & ENGINEERING, 11 (1): 48-58 JAN-FEB 2009

Abstract: Janus is a modular, massively parallel, and reconfigurable FPGA-based computing system that's tailored to a class of hard scientific applications. Monte Carlo statistical mechanics simulations provide a good example of how to use this configurable architecture.

ISSN: 1521-9615

Record 4

Author(s): Belletti, F, Cotallo, M; Cruz, A; Fernandez, LA; Gordillo-Guerrero, A; Guidetti, M; Maiorano, A; Mantovani, F; Marinari, E; Martin-Mayor, V; Sudupe, AM; Navarro, D; Parisi, G; Perez-Gaviro, S; Ruiz-Lorenzo, JJ; Schifano, SF; Sciretti, D; Tarancon, A; Tripiccione, R; Velasco, JL; Yllanes, D

Title: Nonequilibrium Spin-Glass Dynamics from Picoseconds to a Tenth of a Second

Source: PHYSICAL REVIEW LETTERS, 101 (15): Art. No. 157201 OCT 10 2008

Abstract: We study numerically the nonequilibrium dynamics of the Ising spin glass, for a time spanning 11 orders of magnitude, thus approaching the experimentally relevant scale (i.e., seconds). We introduce novel analysis techniques to compute the coherence length in a model-independent way. We present strong evidence for a replicon correlator and for overlap equivalence. The emerging picture is compatible with noncoarsening behavior.

ISSN: 0031-9007

DOI: 10.1103/PhysRevLett.101.157201

Record 3

Author(s): Fernandez, LA (Fernandez, L. A.); Maiorano, A (Maiorano, A.); Marinari, E (Marinari, E.); Martin-Mayor, V (Martin-Mayor, V.); Navarro, D (Navarro, D.); Sciretti, D (Sciretti, D.); Tarancon, A (Tarancon, A.); Velasco, JL (Velasco, J. L.)

Title: Critical properties of the four-state commutative random permutation glassy Potts model in three and four dimensions

Source: PHYSICAL REVIEW B, 77 (10): Art. No. 104432 MAR 2008

Abstract: We investigate the critical properties of the four-state commutative random permutation glassy Potts model in three and four dimensions by means of Monte Carlo simulations and a finite-size scaling analysis. By using a field programmable gate array, we have been able to thermalize a large number of samples of systems with large volume. This has allowed us to observe a spin-glass ordered phase in d=4 and to study the critical properties of the transition. In d=3, our results are consistent with the presence of a Kosterlitz-Thouless transition, but also with different scenarios: transient effects due to a value of the lower critical dimension slightly below 3 could be very important.

ISSN: 1098-0121

DOI: 10.1103/PhysRevB.77.104432

Record 2

Author(s): Belletti, F (Belletti, F.); Cotallo, M (Cotallo, M.); Cruz, A (Cruz, A.); Fernandez, LA (Fernandez, L. A.); Gordillo, A (Gordillo, A.); Maiorano, A (Maiorano, A.); Mantovani, F (Mantovani, F.); Marinari, E (Marinari, E.); Martin-Mayor, V (Martin-Mayor, V.); Munoz-Sudupe, A (Munoz-Sudupe, A.); Navarro, D (Navarro, D.); Perez-Gaviro, S (Perez-Gaviro, S.); Ruiz-Lorenzo, JJ (Ruiz-Lorenzo, J. J.); Schifano, SF (Schifano, S. F.); Sciretti, D (Sciretti, D.); Tarancon, A (Tarancon, A.); Tripiccione, R (Tripiccione, R.); Velasco, JL (Velasco, J. L.)

Title: Simulating spin systems on IANUS, an FPGA-based computer

Source: COMPUTER PHYSICS COMMUNICATIONS, 178 (3): 208-216 FEB 1 2008

Abstract: We describe the hardwired implementation of algorithms for Monte Carlo simulations of a large class of spin models. We have implemented these algorithms as VHDL codes and we have mapped them onto a dedicated processor based on a large FPGA device. The measured performance on one such processor is comparable to 0 (100) carefully programmed high-end PCs: it turns out to be even better for some selected spin models. We describe here codes that we are currently executing on the IANUS massively parallel FPGA-based system. (C) 2007 Elsevier B.V. All rights reserved.

ISSN: 0010-4655

DOI: 10.1016/j.cpc.2007.09.006

Record 1

Author(s): Belletti, F; Campos, I; Maiorano, A; Gaviro, SP; Sciretti, D; Tarancon, A; Velasco, JL; Flor, AC; Navarro, D; Tellez, P; Fernandez, LA; Martin-Mayor, V; Sudupe, AM; Jimenez, S; Marinari, E; Mantovani, F; Poli, G; Schifano, SF; Tripiccione, L; Ruiz-Lorenzo, JJ

Title: Ianus: An adaptive FPGA computer

Source: COMPUTING IN SCIENCE & ENGINEERING, 8 (1): 41-49 JAN-FEB 2006

Abstract: With Ianus, a next-generation field-programmable gate array (FPGA)-based machine, the authors hope to build a system that can fully exploit the performance potential of FPGA devices. A software platform that simplifies Ianus programming will extend its intended application range to a wide class of interesting and computationally demanding problems.

ISSN: 1521-9615