Showing papers by "Áurea R. Vasconcellos published in 1998"
TL;DR: In this article, the Markovian model is applied to a particular model of a spin system in interaction with a thermal bath of lattice vibrations and the limitations of the approach, as well as some criticism it has received, are discussed.
Abstract: The nonlinear quantum kinetic theory for many-body systems either near or far from equilibrium that a nonequilibrium ensemble formalism provides is revisited In this communication we consider an important limit of such transport equations, consisting of the memoryless approximation, which leads to the so-called Markovian kinetic equations They are derived in Zubarev's approach to the method, and next applied to a particular model of a spin system in interaction with a thermal bath of lattice vibrations The limitations of the approach, as well as some criticism it has received, are discussed
49 citations
TL;DR: In this paper, the choice and interpretation of state variables in the thermodynamical description of systems arbitrarily away from equilibrium are discussed. But the authors focus on the case of a particular system consisting of the mobile carriers in a highly excited photo-injected plasma in semiconductors.
Abstract: We address here the question of the choice and interpretation of state variables in the thermodynamical description of systems arbitrarily away from equilibrium. It is presented a discussion of the topic in the framework of informational statistical thermodynamics, an approach based on Gibbs algorithm for nonequilibrium dissipative systems, which provides mechano-statistical foundations to phenomenological theories of irreversible thermodynamics. The theory is applied in the case of a particular system consisting of the mobile carriers in a highly excited photo-injected plasma in semiconductors. The concepts and results thus obtained are tested against experimental data in time-resolved and time-integrated optical laser spectroscopy. It is shown how equilibrium thermodynamic variables are evidenced and measured in such experiments. It is also discussed the influence on them of the inclusion of dissipative fluxes among the basic variables.
41 citations
TL;DR: In this paper, a hierarchy of equations of evolution for a set of basic thermo-hydrodynamic variables, which describe the macroscopic nonequilibrium state of a fluid of bosons, is derived.
Abstract: Within the scope of a nonequilibrium statistical ensemble formalism we derive a hierarchy of equations of evolution for a set of basic thermo-hydrodynamic variables, which describe the macroscopic nonequilibrium state of a fluid of bosons. This set is composed of the energy density and number density and their fluxes of all order. The resulting equations can be considered as far-reaching generalizations of those in Mori’s approach. They involve nonlocality in space and retro-effects (i.e. correlations in space and time respectively), are highly nonlinear, and account for irreversible behavior in the macroscopic evolution of the system. The different contributions to these kinetic equations are analyzed and the Markovian limit is obtained. In the follow up article we consider the nonequilibrium thermodynamic properties that the formalism provides.
34 citations
TL;DR: In this paper, the behavior of the macroscopic thermodynamic state of polymers, centering on acetanilide, was analyzed and the nonlinear equations of evolution for the populations and statistically averaged field amplitudes of CO-stretching modes were derived.
Abstract: We analyze the behavior of the macroscopic thermodynamic state of polymers, centering on acetanilide. The nonlinear equations of evolution for the populations and the statistically averaged field amplitudes of CO-stretching modes are derived. The existence of excitations of the solitary wave type is evidenced. The infrared spectrum is calculated and compared with the experimental data of Careri et al. [Phys. Rev. Lett. 51, 104 (1983)], resulting in a good agreement. We also consider the situation of a nonthermally highly excited sample, predicting the occurrence of a large increase in the lifetime of the solitary wave excitation.
25 citations
TL;DR: In this article, a detailed analysis of a case consisting in a generalized nonequilibrium grand-canonical ensemble is presented, which is quite appropriate to provide a framework for the construction of a non-classical thermo-hydrodynamics.
Abstract: In the domain of Statistical Mechanics of nonequilibrium-nonlinear (dissipative) systems based on a generalized Gibbs–Boltzmann ensemble formalism, it may be highlighted the so-called Nonequilibrium Statistical Operator Method, and, particularly, Zubarev’s approach. We report here a detailed analysis of a case consisting in a generalized nonequilibrium grand-canonical ensemble. Its construction requires to introduce besides the traditional densities of energy and the particle number their nonconserving-dissipative fluxes of all order. The description is quite appropriate to provide a framework for the construction of a nonclassical thermo-hydrodynamics, which is briefly described.
21 citations
19 Oct 1998
TL;DR: In this article, the authors derived and analyzed the informational-statistical thermodynamic properties of a fluid of bosons away from equilibrium, based on the generalized Mori-Heisenberg-Langevin equations.
Abstract: On the basis of the generalized Mori–Heisenberg–Langevin equations presented in the preceding paper, we derive and analyze the informational-statistical thermodynamic properties of a fluid of bosons away from equilibrium. We derive the informational entropy and its production, proceeding to an analysis of the several contributions to these state functions arising out of the evolution of dissipative processes in the system.
20 citations
TL;DR: In this article, a statistical thermodynamics based on a nonequilibrium ensemble formalism is proposed to describe solitary waves arising out of nonlinearity-induced coherence of optical and acoustical vibrational modes in dissipative open systems (polymers and bulk matter).
Abstract: Solitary waves \char22{} arising out of nonlinearity-induced coherence of optical and acoustical vibrational modes in dissipative open systems (polymers and bulk matter) \char22{} are described in terms of a statistical thermodynamics based on a nonequilibrium ensemble formalism. The undistorted progressive wave is coupled to the normal vibrations, and three relevant phenomena follow in sufficiently away-from-equilibrium conditions: (i) A large increase in the populations of the normal modes lowest in frequency, (ii) accompanied by a large increase of the solitary-wave lifetime, and (iii) emergence of a Cherenkov-like effect, consisting in a large emission of phonons in privileged directions, when the velocity of propagation of the soliton is larger than the group velocity of the normal vibrations. Comparison with experiments is presented, which points out to the corroboration of the theory.
19 citations
TL;DR: In this article, the question of the existence of a generalized H-theorem in the context of the variational method in the information-theoretical approach that generates the nonequilibrium statistical operator formalism was considered.
Abstract: We consider the question of the existence of a generalized H-theorem in the context of the variational method in the information-theoretical approach that generates the nonequilibrium statistical operator formalism. After briefly reviewing how the latter provides mechano-statistical foundations for phenomenological irreversible thermodynamics, the so-called Informational Statistical Thermodynamics, we discuss how dissipative phenomena are accounted for by the procedure. Such effects are related to a generalized H-theorem and a weak criterion of positive entropy production. These results are a consequence of the definition of a coarse-grained statistical entropy, resulting from the projection of the full nonequilibrium distribution on the subspace of the slow relaxing dynamical quantities, that are appropriate for the description of the irreversible evolution of the system from the state of initial preparation.
12 citations
Journal Article•
TL;DR: In this article, a mechanostatistical study of the so-called Frohlich effect is presented, namely nonthermal amplification of polar vibrations leading to complex behavior in biosystems, like biopolymers and large aggregates of macromolecules.
Abstract: We present a mechanostatistical study of the so-called Frohlich effect, namely nonthermal amplification of polar vibrations leading to complex behavior in biosystems, like biopolymers and large aggregates of macromolecules. Frohlich condensation is considered to be of relevance for a certain class of biological processes, in particular in connection with the problem of long-range propagation of signals at physiological temperature. Resorting to a thermomechanical theory appropriate to deal with irreversible processes in systems far from equilibrium, earlier results are extended. We perform an analysis of the case when production of a double excitation of polar vibrations, generated by the action of an external pumping source of metabolic energy, is possible. It is shown that, when this is the case, the process involves a positive feedback mechanism that greatly facilitates and enhances the phenomenon of Frohlich's condensation, and consequently the possible accompanying biological processes. The results are discussed and eventual connection with experimental observations pointed out. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 177–187, 1998
12 citations
TL;DR: In this paper, a mechanostatistical study of the so-called Frohlich effect is presented, namely nonthermal amplification of polar vibrations leading to complex behavior in biosystems, like biopolymers and large aggregates of macromolecules.
Abstract: We present a mechanostatistical study of the so-called Frohlich effect, namely nonthermal amplification of polar vibrations leading to complex behavior in biosystems, like biopolymers and large aggregates of macromolecules. Frohlich condensation is considered to be of relevance for a certain class of biological processes, in particular in connection with the problem of long-range propagation of signals at physiological temperature. Resorting to a thermomechanical theory appropriate to deal with irreversible processes in systems far from equilibrium, earlier results are extended. We perform an analysis of the case when production of a double excitation of polar vibrations, generated by the action of an external pumping source of metabolic energy, is possible. It is shown that, when this is the case, the process involves a positive feedback mechanism that greatly facilitates and enhances the phenomenon of Frohlich's condensation, and consequently the possible accompanying biological processes. The results are discussed and eventual connection with experimental observations pointed out. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 177–187, 1998
11 citations
TL;DR: In this article, the so-called Frohlich effect is analyzed in terms of a thermo-mechanical theory, and it is shown that when double (or multiple) processes of excitation of the boson system are possible there follows a positive feedback phenomenon that greatly favors and enhances the effect.
TL;DR: In this paper, the optical properties of photoinjected plasma in semiconductor quantum wires under continuous UV-light illumination are described and the wavenumber-dependent dynamic dielectric function is derived and the Raman scattering cross-section calculated.
TL;DR: In this paper, the authors considered the case of a generalized nonequilibrium grand-canonical ensemble, which requires the introduction of the associated nonconserving dissipative fluxes of all orders.
Abstract: The Nonequilibrium Statistical Operator Method, constructed on the basis of a generalized Gibbs–Boltzmann ensemble formalism, is gaining prominence as an approach to problems in statistical mechanics of nonequilibrium and nonlinear (dissipative) systems. In this paper, we consider the case of a generalized nonequilibrium grand-canonical ensemble. Besides the traditional densities of energy and particle number, this construction requires the introduction of the associated nonconserving dissipative fluxes of all orders.
TL;DR: In this paper, the closure condition for the set of kinetic equations in Zubarev's Nonequilibrium Statistical Operator Method introduces a series of fluxes of a reference set of densities, which are the average values over a Gibbs-like nonequilibrium generalized grand-canonical ensemble of Hermitian operators for fluxes defined at the microscopic-mechanical level.
Abstract: It is shown how the closure condition for the set of kinetic equations in Zubarev's Nonequilibrium Statistical Operator Method introduces a series of fluxes of a reference set of densities. These fluxes are the average values, over a Gibbs-like nonequilibrium generalized grand-canonical ensemble, of Hermitian operators for fluxes defined at the microscopic-mechanical level. The equations of evolution for these fluxes (or equivalently for their conjugated Lagrange multipliers) are described.
TL;DR: In this article, a nonlinear quantum kinetic theory is built within the context of a nonequilibrium statistical ensemble formalism, referred to as MaxEnt-NESOM, and applied to the study of a spin system in interaction with the lattice.
Abstract: We reconsider a nonlinear quantum kinetic theory which is built within the context of a nonequilibrium statistical ensemble formalism. This is the Nonequilibrium Statistical Operator Method based on a variational principle, namely, the Maximization of the Informational-Statistical Entropy, and referred to as MaxEnt-NESOM. It may be considered as encompassed within the framework of E. T. Jaynes' Predictive Statistical Mechanics. These theory has an ample domain of application covering a large class of experimental conditions. We consider a particular ¾ and quite important ¾ limiting case, consisting in the Markovian approximation. For illustration we applied it to the study of a spin system in interaction with the lattice. The presentation is an extended and detailed version of a Brief Report published in Phys. Rev. E 57, 3637-3640 (1998).