Search results for "Non-equilibrium"

Controlled Observation of a Nonequilibrium Ising-Bloch Transition in a Nonlinear Optical Cavity

2004

We describe the controlled observation of the nonequilibrium Ising-Bloch transition in a broad area nonlinear optical cavity, namely, a quasi-1D single longitudinal-mode photorefractive oscilator in a degenerate four-wave mixing configuration. Our experimental technique allows for the controlled injection of the domain walls. We use cavity detuning as control parameter and find that both Ising and Bloch walls can exist for the same detuning values within a certain interval of detunings, i.e., the Ising-Bloch transition is hysteretic in our case. A complex Ginzburg-Landau model is used for supporting the observations.

Domain wall dynamics in an optical Kerr cavity

2004

An anisotropic (dichroic) optical cavity containing a self-focusing Kerr medium is shown to display a bifurcation between static --Ising-- and moving --Bloch-- domain walls, the so-called nonequilibrium Ising-Bloch transition (NIB). Bloch walls can show regular or irregular temporal behaviour, in particular, bursting and spiking. These phenomena are interpreted in terms of the spatio-temporal dynamics of the extended patterns connected by the wall, which display complex dynamical behaviour as well. Domain wall interaction, including the formation of bound states is also addressed.

Effective temperature and scaling laws of polarized quantum vortex bundles

2011

Abstract An effective non-equilibrium temperature is defined for (locally) polarized and dense turbulent superfluid vortex bundles, related to the average energy of the excitations (Kelvin waves) of vortex lines. In the quadratic approximation of the excitation energy in terms of the wave amplitude A, a previously known scaling relation between amplitude and wavelength k of Kelvin waves in polarized bundles, namely A ∝ k − 1 / 2 , follows from the homogeneity of the effective temperature. This result is analogous to that of the well-known equipartition result in equilibrium systems.

Enhanced ferroelectric phase-transition temperature in perovskite-based solid solutions

2004

We explain how the phenomena of ferroelectric phase transition temperature ${T}_{c}$ enhancement beyond the end members in perovskite solid solution such as $\mathrm{Bi}M{\mathrm{O}}_{3}\text{\ensuremath{-}}{\mathrm{PbTiO}}_{3}$ ($M=\mathrm{Sc}$, In, etc.) is related to nonlinear and spatial correlation effects. The explanation is based on the calculation of ${T}_{c}$ in the framework of our random field theory with additional account for nonlinear effects in the above substances. We show that the maximum of ${T}_{c}$ for certain ${\mathrm{PbTiO}}_{3}$ content takes place when coefficient of nonlinearity is positive, the value of this coefficient is found from best fit between theory and ex…

Solvent Effects on Electronically Excited States Using the Conductor-Like Screening Model and the Second-Order Correlated Method ADC(2).

2015

The conductor-like screening model (COSMO) is used to treat solvent effects on excited states within a correlated method based on the algebraic-diagrammatic construction through second-order ADC(2). The origin of solvent effects is revisited, and it is pointed out that two types of contributions have to be considered. One effect is due to the change of the solute's charge distribution after excitation, which triggers a reorganization of the solvent. Initially, only the electronic degrees of freedom adapt to the new charge distribution (nonequilibrium case); for sufficiently long-lived states, the reorientation of the solvent molecules contributes, as well (equilibrium case). The second effe…

Nonlinear nonviscous hydrodynamical models for charge transport in the framework of extended thermodynamic methods

2002

This paper develops a procedure, based on methods of extended thermodynamics, to design nonlinear hydrodynamical models for charge transport in metals or in semiconductors, neglecting viscous phenomena. Models obtained in this way allow the study of the motion of electric charges in the presence of arbitrary external electric fields and may be useful when one wishes to study phenomena in a neighborhood of a stationary nonequilibrium process: indeed, the drift velocity of the charge gas with respect to the crystal lattice is not regarded as a small parameter.

Non-equilibrium thermodynamics analysis of rotating counterflow superfluid turbulence

2010

In two previous papers two evolution equations for the vortex line density $L$, proposed by Vinen, were generalized to rotating superfluid turbulence and compared with each other. Here, the already generalized alternative Vinen equation is extended to the case in which counterflow and rotation are not collinear. Then, the obtained equation is considered from the viewpoint of non-equilibrium thermodynamics. According with this formalism, the compatibility between this evolution equation for $L$ and that one for the velocity of the superfluid component is studied. The compatibility condition requires the presence of a new term dependent on the anisotropy of the tangle, which indicates how the…

Fractional-Order Thermal Energy Transport for Small-Scale Engineering Devices

2014

Fractional-order thermodynamics has proved to be an efficient tool to describe several small-scale and/or high-frequency thermodynamic processes, as shown in many engineering and physics applications. The main idea beyond fractional-order physics and engineering relies on replacing the integer-order operators of classical differential calculus with their real-order counterparts. In this study, the authors aim to extend a recently proposed physical picture of fractional-order thermodynamics to a generic 3D rigid heat conductor where the thermal energy transfer is due to two phenomena: a short-range heat flux ruled by stationary and nonstationary transport equations, and a long-range thermal …

MBPT for the Green's function

2013

Nonequilibrium dressing in a cavity with a movable reflecting mirror

2017

We consider a movable mirror coupled to a one-dimensional massless scalar field in a cavity. Both the field and the mirror's mechanical degrees of freedom are described quantum-mechanically, and they can interact each other via the radiation pressure operator. We investigate the dynamical evolution of mirror and field starting from a nonequilibrium initial state, and their local interaction which brings the system to a stationary configuration for long times. This allows us to study the time-dependent dressing process of the movable mirror interacting with the field, and its dynamics leading to a local equilibrium dressed configuration. Also, in order to explore the effect of the radiation …