Shortcuts of freely relaxing systems using equilibrium physical observables

Many systems, when initially placed far from equilibrium, exhibit surprising behavior in their attempt to equilibrate. Striking examples are the Mpemba effect and the cooling-heating asymmetry. These anomalous behaviors can be exploited to shorten the time needed to cool down (or heat up) a system. Though, a strategy to design these effects in mesoscopic systems is missing. We bring forward a description that allows us to formulate such strategies, and, along the way, makes natural these paradoxical behaviors. This is exemplified with the one-dimensional Ising model in a magnetic field

Temperature chaos is present in off-equilibrium spin-glass dynamics

Experiments featuring non-equilibrium glassy dynamics under temperature changes still await interpretation. There is a widespread feeling that temperature chaos (an extreme sensitivity of the glass to temperature changes) should play a major role but, up to now, this phenomenon has been investigated solely under equilibrium conditions. In fact, the very existence of a chaotic effect in the non-equilibrium dynamics is yet to be established. In this article, we tackle this problem through a large simulation of the 3D Edwards-Anderson model, carried out on the Janus II supercomputer. We find a dynamic effect that closely parallels equilibrium temperature chaos. This dynamic temperature-chaos effect is spatially heterogeneous to a large degree and turns out to be controlled by the spin-glass coherence length xi. Indeed, an emerging length-scale xi* rules the crossover from weak (at xi MUCH LESS-THAN xi*) to strong chaos (xi >> xi*). Extrapolations of xi* to relevant experimental conditions are provided. While temperature chaos is an equilibrium notion that denotes the extreme fragility of the glassy phase with respect to temperature changes, it remains unclear whether it is present in non-equilibrium dynamics. Here the authors use the Janus II supercomputer to prove the existence of dynamic temperature chaos, a nonequilibrium phenomenon that closely mimics equilibrium temperature chaos

Scaling Law describes the spin-glass response in theory, experiments, and simulations

The correlation length xi, a key quantity in glassy dynamics, can now be precisely measured for spin glasses both in experiments and in simulations. However, known analysis methods lead to discrepancies either for large external fields or close to the glass temperature. We solve this problem by introducing a scaling law that takes into account both the magnetic field and the time-dependent spin-glass correlation length. The scaling law is successfully tested against experimental measurements in a CuMn single crystal and against large-scale simulations on the Janus II dedicated computer

Multifractalidad, dinámica exótica, comportamientos de escala y transiciones de fase cuánticas en sistemas complejos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 05/04/2024This thesis, entitled “Multifractality, exotic dynamics, scaling and quantum phase transitionsin complex systems”, focuses on studying the Ising-Lenz and Edward-Anderson models from the numerical point of view. In this study, we have verified how, despite their simplicity, these models can exhibit complex behaviors that still surprise us today. In this sense, numerical simulations have played a crucial role in the detailed exploration of these phenomena, some of which have only been possible through specially dedicated computers such as Janus I and Janus II or through highly optimized programs to be run on GPUs. Part I of this thesis contains an introduction to spin glasses. For this purpose, we givea brief historical introduction followed by the basic concepts of spin glasses, which we complete with a short description of the theoretical concepts of significant relevance for this thesis. Finally, to establish a common methodology, we introduce the different techniques used throughout this dissertation and the fundamental magnitudes that are considered in the different performed analyses...Esta tesis, titulada “Multifractalidad, dinámicas exóticas, comportamientos de escala y transiciones de fase cuánticas en sistemas complejos”, se ha centrado en el estudio de los modelos de Ising-Lenz y Edward-Anderson desde el punto de vista numérico. En este estudio hemos podido comprobar como, a pesar de su sencillez, estos modelos albergan la capacidad de exhibir comportamientos complejos que a día de hoy aún nos sorprenden. En este sentido, el uso de simulaciones numéricas ha desempeñado un papel crucial en la exploración detallada de estos fenómenos, algunas de las cuales sólo han sido posibles mediante el uso de ordenadores especialmente dedicados como Janus I y Janus II, o mediante programas altamente optimizados para ejecutarse en GPUs. La Parte I de esta tesis contiene una introducción a los vidrios de espines. Para ello, damos una breve introducción histórica seguida de los conceptos básicos de los vidrios de espines, que completamos con una breve descripción de los conceptos teóricos de mayor relevancia para esta tesis. Finalmente, a fin de establecer una metodología común, introducimos las distintas técnicas que se emplean a lo largo de esta disertación, así como las magnitudes fundamentales de los distintos análisis realizados...Fac. de Ciencias FísicasTRUEunpu

The QISG suite: high-performance codes for studying quantum ising spin glasses

Está depositada la versión preprint del artículo Program Summary: Program Title: QISG Suite CPC Library link to program files: https://doi.org/10.17632/g97sn2t8z2.1 Licensing provisions: MIT Programming language: CUDA-CWe release a set of GPU programs for the study of the Quantum (S=1/2) Spin Glass on a square lattice, with binary couplings. The library contains two main codes: MCQSG (that carries out Monte Carlo simulations using both the Metropolis and the Parallel Tempering algorithms, for the problem formulated in the Trotter-Suzuki approximation), and EDQSG (that obtains the extremal eigenvalues of the Transfer Matrix using the Lanczos algorithm). EDQSG has allowed us to diagonalize transfer matrices with size up to 236×236. From its side, MCQSG running on four NVIDIA A100 cards delivers a sub-picosecond time per spin-update, a performance that is competitive with dedicated hardware. We include as well in our library GPU programs for the analysis of the spin configurations generated by MCQSG. Finally, we provide two auxiliary codes: the first generates the lookup tables employed by the random number generator of MCQSG; the second one simplifies the execution of multiple runs using different input data.Ministerio de Ciencia, Inovación y Universidades (España)Agencia Estatal de Investigación (España)European Regional Development FundEuropean Research CouncilCentro Nazionale di Ricerca in High-Performance Computing Big Data and Quantum Computing (Italy)The European High Performance ComputingRed Española de SupercomputaciónCentro Nazionale di Ricerca in High-Performance ComputingDepto. de Física TeóricaFac. de Ciencias FísicasTRUEpu

Slow growth of magnetic domains helps fast evolution routes for out-of-equilibrium dynamics

This work was partially supported by Ministerio de Economía, Industria y Competitividad (MINECO, Spain), Agencia Estatal de Investigación (AEI, Spain), and Fondo Europeo de Desarrollo Regional (FEDER, EU) through Grants No. PGC2018-094684-B-C21, No. FIS2017-84440-C2-2-P, and No. MTM2017-84446-C2-2-R. A.L. and J.S. were also partially supported by Grant No. PID2020-116567GB-C22 AEI/10.13039/501100011033. A.L. was also partly supported by Grant No A-FQM-644-UGR20 Programa operativo FEDER Andalucía 2014–2020. J.S. was also partly supported by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M in the line of Excellence of University Professors (EPUC3M23), and in the context of the V PRICIT (Regional Programme of Research and Technological Innovation). I.G.-A.P. was supported by the Ministerio de Ciencia, Innovación y Universidades (MCIU, Spain) through FPU Grant No. FPU18/02665.Cooling and heating faster a system is a crucial problem in science, technology, and industry. Indeed, choosing the best thermal protocol to reach a desired temperature or energy is not a trivial task. Noticeably, we find that the phase transitions may speed up thermalization in systems where there are no conserved quantities. In particular, we show that the slow growth of magnetic domains shortens the overall time that the system takes to reach a final desired state. To prove that statement, we use intensive numerical simulations of a prototypical many-body system, namely, the two-dimensional Ising model.Ministerio de Economía, Industria y Competitividad (MINECO, Spain) Agencia Estatal de Investigación (AEI, Spain) Fondo Europeo de Desarrollo Regional (FEDER, EU) No. PGC2018-094684-B-C21 No. FIS2017-84440-C2-2-P No. MTM2017-84446-C2-2-RPID2020-116567GB-C22 AEI/10.13039/501100011033A-FQM-644-UGR20 FEDER Andalucía 2014–2020Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M in the line of Excellence of University Professors (EPUC3M23)V PRICIT (Regional Programme of Research and Technological Innovation)Ministerio de Ciencia, Innovación y Universidades (MCIU, Spain) through FPU Grant No. FPU18/0266

Numerical test of the replica-symmetric Hamiltonian for correlations of the critical state of spin glasses in a field

A growing body of evidence indicates that the sluggish low-temperature dynamics of glass formers (e.g., supercooled liquids, colloids, or spin glasses) is due to a growing correlation length. Which is the effective field theory that describes these correlations? The natural field theory was drastically simplified by Bray and Roberts in 1980. More than 40 years later, we confirm the tenets of Bray and Roberts’s theory by studying the Ising spin glass in an externally applied magnetic field, both in four spatial dimensions (data obtained from the Janus collaboration) and on the Bethe lattice