Search results for " equilibrium."
showing 10 items of 518 documents
Free-energy barriers for crystal nucleation from fluid phases.
2017
Monte Carlo simulations of crystal nuclei coexisting with the fluid phase in thermal equilibrium in finite volumes are presented and analyzed, for fluid densities from dense melts to the vapor. Generalizing the lever-rule for two-phase coexistence in the canonical ensemble to finite volume, "measurements" of the nucleus volume together with the pressure and chemical potential of the surrounding fluid allows to extract the surface free energy of the nucleus. Neither the knowledge of the (in general non-spherical) nucleus shape nor of the angle-dependent interface tension is required for this task. The feasibility of the approach is demonstrated for a variant of the Asakura-Oosawa model for c…
Relativistic perfect fluids in local thermal equilibrium
2017
Every evolution of a fluid is uniquely described by an energy tensor. But the converse is not true: an energy tensor may describe the evolution of different fluids. The problem of determining them is called here the {\em inverse problem}. This problem may admit unphysical or non-deterministic solutions. This paper is devoted to solve the inverse problem for perfect energy tensors in the class of perfect fluids evolving in local thermal equilibrium (l.t.e.). The starting point is a previous result (Coll and Ferrando in J Math Phys 30: 2918-2922, 1989) showing that thermodynamic fluids evolving in l.t.e. admit a purely hydrodynamic characterization. This characterization allows solving this i…
Memory effects in the relaxation of the Gaussian trap model
2011
We investigate the memory effect in a simple model for glassy relaxation, a trap model with a Gaussian density of states. In this model thermal equilibrium is reached at all finite temperatures and therefore we can consider jumps from low to high temperatures in addition to the quenches usually considered in aging studies. We show that the evolution of the energy following the Kovacs-protocol can approximately be expressed as a difference of two monotonously decaying functions and thus show the existence of a so-called Kovacs hump whenever these functions are not single exponentials. It is well established that the Kovacs effect also occurs in the linear response regime and we show that mos…
Probing spectral properties of the QGP with real-time lattice simulations
2018
We present a new method to obtain spectral properties of a non-Abelian gauge theory in the region where occupation numbers are high. The method to measure the (single-particle) spectral function is based on linear response theory and classical-statistical lattice simulations. Although we apply it to a system far from equilibrium in a self-similar regime, the extracted spectral function can be understood within the hard thermal loop (HTL) formalism and can thus be connected to thermal equilibrium at high temperatures. This allows us to obtain quantities like the lifetime of quasiparticles that are beyond the leading order and difficult to compute within HTL. The approach has the potential to…
Black Hole Evaporation by Thermal Bath Removal
1996
We study the evaporation process of 2D black holes in thermal equilibrium when the incoming radiation is turned off. Our analysis is based on two different classes of 2D dilaton gravity models which are exactly solvable in the semiclassical aproximation including back-reaction. We consider a one parameter family of models interpolating between the Russo-Susskind-Thorlacius and Bose-Parker-Peleg models. We find that the end-state geometry is the same as the one coming from an evaporating black hole formed by gravitational collapse. We also study the quantum evolution of black holes arising in a model with classical action $S = {1\over2\pi} \int d^2x \sqrt{-g} (R\phi + 4\lambda^2e^{\beta\phi}…
Nonlinearity and Disorder in the Statistical Mechanics of Integrable Systems
1992
Attention is drawn to a theory of the statistical mechanics (SM) of the integrable models in 1+1 dimension — a theory of ‘soliton statistical mechanics’ classical and quantum [1–17]. This SM provides a generic example of integrable nonlinearity interacting with disorder. In the generic classical examples, such as the classical SM of the sine-Gordon model, phonons provide disorder in which sit coherent structures — the kink-like solitons. But these solitons are dressed by the disorder, in equilibrium, while the breather-like solitons break up to form the disordered structures which are the phonons in thermal equilibrium. On the other hand quantum solitons, dressed by both the vacuum and fini…
Constant-adiabaticity pulse schemes for manipulating singlet order in 3-spin systems with weak magnetic non-equivalence
2021
Abstract Parahydrogen-induced polarization (PHIP) is a source of nuclear spin hyperpolarization, and this technique allows for the preparation of biomolecules for in vivo metabolic imaging. PHIP delivers hyperpolarization in the form of proton singlet order to a molecule, but most applications require that a heteronuclear (e.g. 13C or 15N) spin in the molecule is hyperpolarized. Here we present high field pulse methods to manipulate proton singlet order in the [1-13C]fumarate, and in particular to transfer the proton singlet order into 13C magnetization. We exploit adiabatic pulses, i.e., pulses with slowly ramped amplitude, and use constant-adiabaticity variants: the spin Hamiltonian is va…
Modelling of Boltzmann transport equation for freeze-out
2005
The freeze-out (FO) in high-energy heavy-ion collisions is assumed to be continuous across finite layer in space–time. Particles leaving local thermal equilibrium start to freeze out gradually till they leave the layer, where all the particles are frozen out. To describe such a kinetic process we start from Boltzmann transport equation (BTE). However, we will show that the basic assumptions of BTE, such as molecular chaos or spatial homogeneity do not hold for the above-mentioned FO process. The aim of the presented work is to analyse the situation, discuss the modification of BTE and point out the physical causes, which yield to these modifications of BTE for describing FO.
Spin-lattice relaxation of individual solid-state spins
2018
Understanding the effect of vibrations on the relaxation process of individual spins is crucial for implementing nanosystems for quantum information and quantum metrology applications. In this work, we present a theoretical microscopic model to describe the spin-lattice relaxation of individual electronic spins associated to negatively charged nitrogen-vacancy centers in diamond, although our results can be extended to other spin-boson systems. Starting from a general spin-lattice interaction Hamiltonian, we provide a detailed description and solution of the quantum master equation of an electronic spin-one system coupled to a phononic bath in thermal equilibrium. Special attention is given…
Slowing down in the three-dimensional three-state Potts glass with nearest neighbor exchange : A Monte Carlo study
1998
,Static and dynamic properties of the Potts model on the simple cubic lattice with nearest neighbor ±Ĵ-interaction are obtained from Monte Carlo simulations in a temperature range where full thermal equilibrium still can be achieved (T/Ĵ ≥ 0.6). For a lattice size L = 16, in this range finite size effects are still negligible, but the data for the spin glass susceptibility agree with previous extrapolations based on finite size scaling of very small lattices. While the static properties are compatible with a zero temperature transition, they certainly do not prove it. Unlike the Ising spin glass, the decay of the time-dependent order parameter is compatible with a simple Kohlrausch function…