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An efficient method for computing thermodynamic equilibrium states at the micromagnetic length scale is introduced, using the Markov chain Monte Carlo method. Trial moves include not only rotations of vectors, but also a change in their…

Mesoscale and Nanoscale Physics · Physics 2021-11-10 Serban Lepadatu

We develop an unconditionally energy-stable tensor-product space-time discretization framework for the solution of a linear kinetic transport equation in one space dimension. The kinetic equation is a simplified model of radiative transfer…

Numerical Analysis · Mathematics 2026-04-24 Anita Gjesteland , Sigrun Ortleb , Salim Elghawi , David C. Del Rey Fernández

We present a macroscopic model of the decay of a coherent classical scalar field into statistical fluctuations through the process of parametric amplification. We solve the field theory (henceforth,"microscopic") model to leading order in a…

High Energy Physics - Phenomenology · Physics 2007-05-23 Esteban Calzetta , Marc Thibeault

The two-dimensional Ising model with fixed magnetization is studied using Monte Carlo techniques. At the coexistence line, the macroscopic, extensive droplet of minority spins becomes thermally unstable by breaking up into microscopic…

Statistical Mechanics · Physics 2009-10-31 M. Pleimling , W. Selke

We investigate the thermally activated magnetization switching of small ferromagnetic particles driven by an external magnetic field. For low uniaxial anisotropy the spins can be expected to rotate coherently, while for sufficient large…

Statistical Mechanics · Physics 2009-10-31 D. Hinzke , U. Nowak

The magnetic relaxation of ferromagnetic powders has been studied for many years, largely due to its importance to recording technologies. However, only recently have experiments been performed that resolve the magnetic state of individual…

Condensed Matter · Physics 2009-10-22 Howard L. Richards , Scott W. Sides , M. A. Novotny , Per Arne Rikvold

The quantum behaviour of the electromagnetic field in mesoscopic elements is intimately linked to the quantization of the charge. In order to probe nonclassical aspects of the field in those elements, it is essential that thermal noise be…

Quantum Physics · Physics 2018-05-01 Stéphane Virally , Jean Olivier Simoneau , Christian Lupien , Bertrand Reulet

Linear magnetization dynamics in the presense of a thermal bath is analyzed for two general classes of microscopic damping mechanisms. The resulting stochastic differential equations are always in the form of a damped harmonic oscillator…

Statistical Mechanics · Physics 2007-05-23 Vladimir L. Safonov , H. Neal Bertram

We introduce a mesocopic modeling approach for active systems. The continuum model allows to consider microscopic details as well as emerging macroscopic behavior and can be considered as a minimal continuum model to describe generic…

Soft Condensed Matter · Physics 2016-08-24 Francesco Alaimo , Simon Praetorius , Axel Voigt

We develop a numerical model that reproduces the thermal equilibrium and the spin transfer mechanisms in magnetic nanomaterials. We analyze the coherent two-particle spin exchange interaction and the electron-electron collisions. Our study…

Mesoscale and Nanoscale Physics · Physics 2021-04-01 O. Morandi

Atomic scale simulations at finite temperature are an ideal approach to study the thermodynamic properties of magnetic transition metals. However, the development of interatomic potentials explicitly taking into account magnetic variables…

We study numerically the thermalisation and temporal evolution of the reduced density matrix for a two-site subsystem of a fermionic Hubbard model prepared far from equilibrium at a definite energy. Even for very small systems near quantum…

Quantum Physics · Physics 2011-01-24 S. Genway , A. F. Ho , D. K. K. Lee

In this work, we are interested in the behaviour of a single ferromagnetic mono--domain particle submitted to an external field with a stochastic perturbation. This model is a step toward the mathematical understanding of thermal effects on…

Probability · Mathematics 2016-06-27 Stéphane Labbé , Jérôme Lelong

We consider the time evolution of entanglement in a finite two dimensional transverse Ising model. The model consists of a set of 7 localized spin-1/2 particles in a two dimensional triangular lattice coupled through nearest neighbor…

Quantum Physics · Physics 2015-03-18 Qing Xu , Gehad Sadiek , Sabre Kais

Concepts of everyday use like energy, heat, and temperature have acquired a precise meaning after the development of thermodynamics. Thermodynamics provides the basis for understanding how heat and work are related and with the general…

Statistical Mechanics · Physics 2007-05-23 D. Reguera , J. M. Rubi , J. M. G. Vilar

A key feature of non-equilibrium thermodynamics is the Markovian, deterministic relaxation of coarse observables such as, for example, the temperature difference between two macroscopic objects which evolves independently of almost all…

Quantum Physics · Physics 2014-04-08 Hendrik Niemeyer , Kristel Michielsen , Hans de Raedt , Jochen Gemmer

A family of multispecies Ising models on generalized regular random graphs is investigated in the thermodynamic limit. The architecture is specified by class-dependent couplings and magnetic fields. We prove that the magnetizations,…

Mathematical Physics · Physics 2024-03-22 Diego Alberici , Pierluigi Contucci , Emanuele Mingione , Filippo Zimmaro

We discuss numerical and theoretical results for models of magnetization switching in nanoparticles and ultrathin films. The models and computational methods include kinetic Ising and classical Heisenberg models of highly anisotropic…

Materials Science · Physics 2007-05-23 Per Arne Rikvold , Gregory Brown , Steven J. Mitchell , M. A. Novotny

We propose a new concept of weak solution to the equations of compressible magnetohydrodynamics driven by large boundary data. The system of the underlying field equations is solvable globally in time in the out of equilibrium regime…

Analysis of PDEs · Mathematics 2023-04-04 Eduard Feireisl , Piotr Gwiazda , Young-Sam Kwon , Agnieszka Świerczewska-Gwiazda

We analytically model the magnetization switching time of a biaxial ferromagnet driven by an antidamping-like spin torque. The macrospin magnetization dynamics is mapped to an energy-flow equation, wherein a rational-function approximation…

Applied Physics · Physics 2020-05-13 Ankit Shukla , Arun Parthasarathy , Shaloo Rakheja