Person:
Fernández Pérez, Luis Antonio

First Name

Luis Antonio

Last Name

Fernández Pérez

URI

https://hdl.handle.net/20.500.14352/75087

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Department

Física Teórica

Area

Física Teórica

Identifiers

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Now showing 1 - 10 of 21

Off-equilibrium fluctuation-dissipation relations in the 3d Ising spin glass in a magnetic field
(Physical review B, 2003) Cruz, A.; Fernández Pérez, Luis Antonio; Jiménez, S.; Ruiz Lorenzo, J. J.; Tarancón, A.
We study the fluctuation-dissipation relations for a three dimensional Ising spin glass in a magnetic field both in the high temperature phase as well as in the low temperature one. In the region of times simulated we have found that our results support a picture of the low temperature phase with broken replica symmetry, but a droplet behavior cannot be completely excluded.
Critical behavior in the site-diluted three-dimensional three-state Potts model
(Physical review B, 2000) Ballesteros, H. G.; Fernández Pérez, Luis Antonio; Martín Mayor, Víctor; Muñoz Sudupe, Antonio; Parisi, G.; Ruiz Lorenzo, J. J.
We have studied numerically the effect of quenched site dilution on a weak first-order phase transition in three dimensions. We have simulated the site diluted three-states Potts model studying in detail the secondorder region of its phase diagram. We have found that the n exponent is compatible with the one of the three-dimensional diluted Ising model, whereas the h exponent is definitely different.
First Order Phase Transition in a 3D disordered system
(AIP conference proceedings: large scale simulations of complex systems, condensed matter and fusion plasma, 2008) Fernández Pérez, Luis Antonio; Gordillo Guerrero, A.; Martín Mayor, Víctor; Ruiz Lorenzo, J. J.
We present a detailed numerical study on the effects of adding quenched impurities to a three dimensional system which in the pure case undergoes a strong first order phase transition (specifically, the ferromagnetic/paramagnetic transition of the site-diluted four states Potts model). We can state that the transition remains first-order in the presence of quenched disorder (a small amount of it) but it turns out to be second order as more impurities are added. A tricritical point, which is studied by means of Finite-Size Scaling, separates the first-order and second-order parts of the critical line. The results were made possible by a new definition of the disorder average that avoids the diverging-variance probability distributions that arise using the standard methodology. We also made use of a recently proposed microcanonical Monte Carlo method in which entropy, instead of free energy, is the basic quantity.
Instanton-like contributions to the dynamics of Yang-Mills fields on the twisted torus
(1993) García Pérez, M.; González Arroyo, A.; Martínez, P.; Fernández Pérez, Luis Antonio; Muñoz Sudupe, Antonio; Ruiz Lorenzo, J. J.; Azcoiti, V.; Campos, I.; Ciria, J.C.; Cruz, A.; Íñiguez, D.; Lesmes, F.; Badoni, D.; Pech, J.
We study SU(2) lattice gauge theory in small volumes and with twist m ⃗ = (1, 1, 1). We investigate the presence of the periodic instantons of Q = 1/2 and determine their free energy and their contribution to the splitting of energy flux sectors E(e ⃗ = (1, 1, 1)) − E(e ⃗ = (0, 0, 0)).
Scaling corrections: site percolation and Ising model in three dimensions
(Journal of Physics A-Mathematical and General, 1999) Ballesteros, H.G.; Fernández Pérez, Luis Antonio; Martín Mayor, Víctor; Muñoz Sudupe, Antonio; Parisi, G.; Ruiz Lorenzo, J. J.
Using Finite-Size Scaling techniques we obtain accurate results for critical quantities of the Ising model and the site percolation, in three dimensions. We pay special attention in parameterizing the corrections-to-scaling, what is necessary to put the systematic errors below the statistical ones.
Measures of critical exponents in the four-dimensional site percolation
(Physics letters B, 1997) Ballesteros, H. G.; Fernández Pérez, Luis Antonio; Martín Mayor, Víctor; Muñoz Sudupe, Antonio; Parisi, G.; Ruiz Lorenzo, J. J.
Using finite-size scaling methods we measure the thermal and magnetic exponents of the site percolation in four dimensions, obtaining a value for the anomalous dimension very different from the results found in the literature. We also obtain the leading corrections-to-scaling exponent and, with great accuracy, the critical density.
A proposal of a Monte Carlo renormalization group transformation
(Nuclear Physics B-Proceedings Supplements, 1995) Fernández Pérez, Luis Antonio; Muñoz Sudupe, Antonio; Ruiz Lorenzo, J. J.; Tarancón, A.
We propose a family of renormalization group transformations characterized by free parameters that may be tuned in order to reduce the truncation effects. As a check we test them in the three dimensional XY model. The Schwinger-Dyson equations are used to study the renormalization group flow.
Microcanonical finite-size scaling in second-order phase transitions with diverging specific heat
(Physical review E, 2009) Fernández Pérez, Luis Antonio; Gordillo Guerrero, A.; Martín Mayor, Víctor; Ruiz Lorenzo, J. J.
A microcanonical finite-size ansatz in terms of quantities measurable in a finite lattice allows extending phenomenological renormalization the so-called quotients method to the microcanonical ensemble. The ansatz is tested numerically in two models where the canonical specific heat diverges at criticality, thus implying Fisher renormalization of the critical exponents: the three-dimensional ferromagnetic Ising model and the two-dimensional four-state Potts model (where large logarithmic corrections are known to occur in the canonical ensemble). A recently proposed microcanonical cluster method allows simulating systems as large as L = 1024 Potts or L= 128 (Ising). The quotients method provides accurate determinations of the anomalous dimension, η, and of the (Fisher-renormalized) thermal ν exponent. While in the Ising model the numerical agreement with our theoretical expectations is very good, in the Potts case, we need to carefully incorporate logarithmic corrections to the microcanonical ansatz in order to rationalize our data.
Numerical construction of the Aizenman-Wehr metastate
(Physical review letters, 2017) Billoire,, A.; Fernández Pérez, Luis Antonio; Maiorano, A.; Marinari, E.; Martín Mayor, Víctor; Moreno Gordo, J.; Parisi, G.; Ricci-Tersenghi, F.; Ruiz Lorenzo, J. J.
Chaotic size dependence makes it extremely difficult to take the thermodynamic limit in disordered systems. Instead, the metastate, which is a distribution over thermodynamic states, might have a smooth limit. So far, studies of the metastate have been mostly mathematical. We present a numerical construction of the metastate for the d ¼ 3 Ising spin glass. We work in equilibrium, below the critical temperature. Leveraging recent rigorous results, our numerical analysis gives evidence for a dispersed metastate, supported on many thermodynamic states.
Dynamic variational study of chaos: spin glasses in three dimensions
(Journal of Statistical Mechanics: theory and experiment, 2018) Fernández Pérez, Luis Antonio; Martín Mayor, Víctor; Billoire, A.; Maiorano, A.; Marinari, E.; Moreno Gordo, J.; Parisi, G.; Ricci-Tersenghi, F.; Ruiz Lorenzo, J. J.
We have introduced a variational method to improve the computation of integrated correlation times in the Parallel Tempering Dynamics, obtaining a better estimate (a lower bound, at least) of the exponential correlation time. Using this determination of the correlation times, we revisited the problem of the characterization of the chaos in temperature in finite dimensional spin glasses spin by means of the study of correlations between different chaos indicators computed in the static and the correlation times of the Parallel Tempering dynamics. The sample-distribution of the characteristic time for the Parallel Tempering dynamics turns out to be fat-tailed and it obeys finite-size scaling.