Off equilibrium dynamics in the 2d-XY system

The fabrication and the study of sol gel-microcavities strongly doped with CdSe nanocrystals are presented. The Fabry-Perot microcavities are formed by a Distributed Bragg Reflector covered with a CdSe doped active layer and a silver mirror. These microcavities are studied with reflectometry experiments. We observe that the cavity resonance peak is enlarged by a factor two when his spectral position corresponds to the first absorption line of the CdSe nanocrystals. Transfer matrix method calculation taking into account the CdSe absorption have been performed and are in good agreement with the experimental values.Received: 23 July 2004, Published online: 26 November 2004PACS: 78.67. Bf Nanocrystals and nanoparticules - 81.07.-b Nanoscale materials and structures: fabrication and characterization     

Off equilibrium dynamics in the 3d-XY system

We investigate through Monte Carlo simulations the non-equilibrium behaviour of the three-dimensional XY-model quenched from a high temperature state to its ferromagnetic and critical phases. The two-times autocorrelation and response functions are determined in the asymptotic (scaling) regime, from which the nonequilibrium exponents and critical are extracted. The form of the scaling function is in agreement with the prediction of local scale-invariance. The so-called limit fluctuation-dissipation ratio is shown to vanish in the ordered phase and to reach a constant value around 0.43 for the critical quench.Received: 12 July 2004, Published online: 30 September 2004PACS: 75.40.Gb Dynamic properties - 05.70.Ln Non-equilibrium and irreversible thermodynamics     

Off equilibrium dynamics in disordered quantum spin chain

We study the non-equilibrium time evolution of the average transverse magnetisation and end-to-end correlation functions of the random Ising quantum chain. Starting with fully magnetised states, either in the x or z direction, we compute numerically the average quantities. They show similar behaviour to the homogeneous chain, that is an algebraic decay in time toward a stationary state. During the time evolution, the spatial correlations, measured from one end to the other of the chain, are building up and finally at long time they reach a size-dependent constant depending on the distance from criticality. Analytical arguments are given which support the numerical results. Received 11 July 2002 / Received in final form 9 September 2002 Published online 29 October 2002     

Vapour-liquid equilibrium in the krypton-xenon system

Isothermal vapour-liquid data were measured for the krypton-xenon system at ten temperatures between 165 and 270 K and pressures to 6.7 MPa, using a vapour recirculating technique. The mixture critical line has been located in (P, T, x) space. Barker's method of data reduction has been used to test the thermodynamic consistency of isotherms below the critical temperature of krypton (209.4 K) and the excess Gibbs energy was evaluated, at the same temperatures, as a function of composition. The results of the experiments have been compared with predictions of the Peng-Robinson equation of state. With interaction parameter calculated by fitting the isotherm of 200.64 K, this equation predicts the liquid and vapour phase compositions to within about a few mole per cent over most of the experimental range.     

Phase diagram and thermodynamic equilibrium in the Fe x TiSe2 system

Phase diagram has been refined by the quenching method; the phase composition has been monitored by NGR spectroscopy. The experimental data agree well with theoretical predictions on the relation of the phase diagram with the character of a chemical bond. It has been shown that the system is essentially nonquasi-binary because of the selenium exchange between the precipitated iron and the matrix lattice.     

Study of equilibrium using collision dynamics

We discuss the possibility of equilibrium (and thermalization) in heavy-ion collisions at intermediate energies within a transport model. This was achieved by dividing the nuclear matter into different collision zones. We find that those nucleons which experience at least ten collisions are close to complete equilibrium whereas others never achieve any equilibrium.     

Punctuated equilibrium and power law in economic dynamics

This work is primarily based on a recently proposed toy model by Thurner et al. (2010) [3] on Schumpeterian economic dynamics (inspired by the idea of economist Joseph Schumpeter [9]). Interestingly, punctuated equilibrium has been shown to emerge from the dynamics. The punctuated equilibrium and Power law are known to be associated with similar kinds of biologically relevant evolutionary models proposed in the past. The occurrence of the Power law is a signature of Self-Organised Criticality (SOC). In our view, power laws can be obtained by controlling the dynamics through incorporating the idea of feedback into the algorithm in some way. The so-called ‘feedback’ was achieved by introducing the idea of fitness and selection processes in the biological evolutionary models. Therefore, we examine the possible emergence of a power law by invoking the concepts of ‘fitness’ and ‘selection’ in the present model of economic evolution.     

Approach to equilibrium of Glauber dynamics in the one phase region

Various finite volume mixing conditions in classical statistical mechanics are reviewed and critically analyzed. In particular somefinite size conditions are discussed, together with their implications for the Gibbs measures and for the approach to equilibrium of Glauber dynamics inarbitrarily large volumes. It is shown that Dobrushin-Shlosman's theory ofcomplete analyticity and its dynamical counterpart due to Stroock and Zegarlinski, cannot be applied, in general, to the whole one phase region since it requires mixing properties for regions ofarbitrary shape. An alternative approach, based on previous ideas of Oliveri, and Picco, is developed, which allows to establish results on rapid approach to equilibrium deeply inside the one phase region. In particular, in the ferromagnetic case, we considerably improve some previous results by Holley and Aizenman and Holley. Our results are optimal in the sene that, for example, they show for the first time fast convergence of the dynamicsfor any temperature above the critical one for thed-dimensional Ising model with or without an external field. In part II we extensively consider the general case (not necessarily attractive) and we develop a new method, based on renormalizations group ideas and on an assumption of strong mixing in a finite cube, to prove hypercontractivity of the Markov semigroup of the Glauber dynamics.Work partially supported by grant SCi-CT91-0695 of the Commission of European Communities     

Internal equilibrium and crystal dynamics of tantalum

A lattice dynamical model for bcc metals, which satisfies the internal force equilibrium condition of the lattice is proposed. The present model combines a linearized Thomas-Fermi Theory for the electron-ion interaction and the central pair potential for ion-ion interaction. as an application, the computed phonon dispersion, vibrational spectrum, and lattice specific heat of tantalum show fairly good agreement with experiments.     

Lifshitz-Safran coarsening dynamics in a 2D hexagonal system

The coarsening process in a two-dimensional hexagonal system in the region close to both spinodal and order-order transitions was investigated through the Cahn-Hilliard model. We found a distinctive region of the phase diagram where the pinning of dislocations plays only a minor role and the dynamics is led by the triple points. In this region, we found configurations of domains with the same features as those proposed by Lifshitz. As a consequence, different correlation lengths grow logarithmically in time, in good agreement with the predictions of coarsening at low temperatures proposed by Safran.     

Return to equilibrium and stability of dynamics (semigroup dynamics case)

A study is presented of asymptotically normal dynamical semigroups for which there exists a faithful normal state satisfying the detailed balance condition. Such dynamics reveals a return to a stationary state if additionally a weak cluster property is assumed. The generalized stability condition and generalized wave operators are introduced. The theory is illustrated by models.     

Field-theoretic approach to critical dynamics far from equilibrium

The field-theoretic approach to critical phenomena is extended to deal with critical dynamics far from equilibrium. In particular, the macroscopic evolution equation for the average order parameter is derived in a manner parallel to the derivation of the equation of state. The method is illustrated by deriving the scaled macroscopic equation of motion for the timedependent Ginzburg-Landau model near the critical point for dimensionality near four.     

On the Swendsen-Wang dynamics. I. Exponential convergence to equilibrium

We present rigorous results on the exponential convergence to equilibrium for the Swendsen-Wang stochastic dynamics for thed-dimensional Ising ferromagnet with external magnetic fieldh in the thermodynamic limit. We consider various situations, mainly in the low-temperature regime, in which boundary conditions are homogeneous and parallel or opposite to the external field. In the latter case we relate directly the tunneling from the metastable phase to the stable one with the exponential convergence to equilibrium.     

Role of unstable directions in the equilibrium and aging dynamics of supercooled liquids

The connectivity of the potential energy landscape in supercooled atomic liquids is investigated through a calculation of the instantaneous normal modes spectrum and a detailed analysis of the unstable directions in configuration space. We confirm the hypothesis that the mode-coupling critical temperature is the T at which the dynamics crosses over from free to activated exploration of configuration space. We also observe changes in the local connectivity of configuration space sampled during aging, following a temperature jump from a liquid to a glassy state.     

Interphase ionic equilibrium in a model system

For a system consisting of two phases between which charged particles are exchanged, we obtained expressions for the electrochemical potentials of the particles in the two phases. In the case of a blurred double layer, the equilibrium condition differs from the analogous condition used to study contact phenomena in solid-state physics.Tomsk Polytechnical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 97–101, December, 1992.