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This article addresses the problem of an efficient description of the transient electron transport in (primarily small open) quantum systems out of equilibrium. It provides an overview and critical review of the use of causal Ansatzes with the accent on derivation of (quantum) transport equations from the standard Kadanoff–Baym (KB) equations for the non-equilibrium Green’s functions (NEGF). The family of causal Ansatzes originates from the well-known Generalized Kadanoff–Baym Ansatz (GKBA). The Ansatz technique has been fairly successful in practice. Recently, the scope of the method has been extended towards more “difficult” cases and its success can be assessed more precisely. This general picture is demonstrated and analyzed in detail for a variant of the generic molecular island model, an Anderson impurity linked between two bulk metallic leads by tunneling junctions. First, the KB equations are reduced to a non-Markovian generalized master equation (GME) by means of a general causal Ansatz. Further reduction to a Markovian master equation is achieved by partly relaxing the strictly causal character of the theory. For the model narrowed down to ferromagnetic leads, the transient currents are spin polarized and the tunneling functions have a complex spectral structure. This has prompted deriving explicit conditions for the use of an Ansatz. To extend the applicability range of the GME, approximate vertex corrections to the Ansatz were introduced and used with success. Finally, the relation of the GME description to possible non-equilibrium generalizations of the fluctuation–dissipation theorem is shown, extended beyond the present model within the NEGF formalism and physically interpreted in terms of a simplified kinetic theory of non-equilibrium electrons in open quantum systems.

In the present paper, we analyze the role of extracellular tissue (ECT) in signal transfer and information processing in biological neural networks. Our speculative approach, which is based mainly on the facts taken from the literature, is completed by simple original models and quantitative estimates. It is shown that the presence of ECT controls some fundamental parameters of immersed biological neural network, which are traditionally treated as intrinsic to neuron membranes. We then propose that the diffusive transfer of action potential via the nervous fiber together with processes induced in the surrounding ECT, is ultimately controlled, in contrast to the standard paradigm, by the quantum diffusion of $$\hbox {Na}^{{+}}$$ and $$\hbox {K}^{{+}}$$ ions, which minimizes the heat production in nervous tissue. Furthermore the diffusion of polarization wave along the axon membrane excites in surrounding ECT temporal potential distribution, which can bias the synapses and dendrites of all vicinal neurons. We claim that just this, so-called, ephaptic coupling between neighboring neurons, completes the local neural network and in fact is responsible for information processing there. Such an idea is obviously incompatible with current models of neural networks of McCulloch–Pitts’ and Rosenblatt’s type, which assume that the information processing takes place exclusively within the neuron soma, being thus convenient merely for the description of artificial neural networks.

The governing theory of electric signal transfer through nerve fibre, as established by Hodgkin and Huxley in the 1950s, uses for the description of action potential a clever combination of various concepts of electrochemistry and circuit theory; however, this theory neglects some fundamental features of charge transport through any conductor, e.g., the existence of a temporary charged layer on its boundary accompanied by an external electric field. The consequences of this fact are, among others, the introduction of a non-adequate concept of “conduction velocity” and the obscure idea of saltatory propagation of action potential in myelinaed nerve fibres. Our approach, based on standard transport theory and, particularly, on the submarine cable model, describes the movement of the front of the action potential as a diffusion process characterized by the diffusion constant DE. This process is physically realized by the redistribution of ions in the nervous fluid (axoplasm), which is controlled by another diffusion constant DΩ ≪ DE. Since the action bound with the movement of Na+ and K+ cations prevailing in the axoplasm is comparable with the Planck constant ℏ (i.e. DΩ → ℏ∕2M, where M is ion mass), signal transfer is actually a quantum process. This fact accounts for the astonishing universality of the transfer of action potential, which is proper to quite different species of animals. As is further shown, the observed diversity in the behaviour of nerve tissues is controlled by the scaling factor $$\sqrt{(D_{\Omega} / D_E)}$$ , where DΩ is of a quantum nature and DE of an essentially geometric one.

Presented is a brief overview of recent developments of topics addressed by the reviews and original papers of this volume related to non-equilibrium phenomena in various (especially mesoscopic) systems and the foundations of quantum physics.

This text presents a brief overview of the recent development of topics addressed by the original papers of this volume related to non-equilibrium phenomena in various (especially mesoscopic) systems and the foundations of quantum physics. A selection of relevant literature is included.

Transient magnetic currents between two ferromagnetic electrodes linked by tunneling junctions to a molecular size island are calculated. The island is represented by an Anderson type local center. The tunneling spectral functions simulate nickel. Transient magnetic currents under a constant galvanic bias between the electrodes are invoked by sudden switching of the junctions. The process is treated numerically using the non-equilibrium Greens functions (NEGF) (Kalvova et al., J. Supercon. Novel Mag. 26, 773, 2013, J. Supercon. Novel Mag. 28, 1087, 2015) from the early stages of the transient depending on the finite time initial conditions to the late asymptotics of free relaxation to the steady state. This serves as a reference for testing the simpler and physically transparent description by a generalized master equation, resulting from the NEGF scheme approximated by the Generalized Kadanoff-Baym Ansatz (GKBA) (Spicka et al., Internat. J. Mod. Phys. 28 1430013-1, 2014). It turns out that decisive for the applicability of GKBA is the spectral structure of tunneling functions and their positioning with respect to the island level dependent on the bias and the exchange splitting. Favorable for the validity of GKBA are weak tunneling and spectrally flat tunneling functions. Stretching of these conditions toward the realistic situation for transition metal electrodes with their complex sd surface-modified spectral properties is limited.

The choice of the mathematical structure of physical quantities, which is natural for the description of finite physical reality and related problems, is discussed from the historical and the epistemological points of view. We show that for the establishment of physical quantities is fully sufficient the system of rational numbers which are equivalent to the finite ordered sets of integers, while the currently used system of real numbers is quite redundant for such a purpose. These facts may have far reaching consequences not only for pure epistemology but for the interpretation of many fundamental physical phenomena as well. Finally, the relation between the chosen structure of physical quantities and the so-called Principle of conformity of physics and mathematics is shortly discussed.

This paper extends our recent theoretical study Kalvova et al. (J. Supercon. and Novel Mag. 26, 773 2013) of transient currents through molecular bridges to magnetic tunneling. We calculate the excess magnetization on a molecular bridge shunting the magnetic junction. The system is represented by two ferromagnetic electrodes bridged by a molecular size island with a few discrete electronic levels and a local Hubbard type correlation. The island is linked to the electrodes by tunneling junctions. One of the junctions is permanent, the coupling strength of the other one is assumed to undergo rapid changes modulating the connectivity of the system. The sudden switching events give rise to transient magnetic currents resulting in changes of magnetization at the island. They vary with the constant galvanic bias between the electrodes. Depending on the time scale of the switching series, the transients are dominated by the initial quantum correlations, or reach the kinetic stage controlled by a simple relaxation mechanism. We employ the nonequilibrium Green’s functions. The finite-time correlated initial conditions are taken into account using the partitioning-in-time method we developed previously Velický et al. (Phys. Rev. B 81, 235116 2010). The numerical solution is obtained solving the real-time Dy-son equation in the integro-differential form self-consistently. For long time asymptotic, a generalized master equation is matched to the initial stage solution.

We consider current flow between two metallic leads joined by tunneling junctions to a molecular island. The junctions are assumed to be “wiggly,” that is, switching on and off intermittently. The resulting sequence of current transients overlaps in dependence on the interplay between the switching times and the decay time of “initial” correlations induced by each switching event. The process is described in terms of nonequilibrium Green’s functions.

The equations for the Non-Equilibrium Green's Functions (NEGF) describing the electron transport through molecular bridges are commonly reduced to a Generalized Master Equation (GME) for the one-electron density matrix using the Generalized Kadanoff-Baym Ansatz (GKBA). This works for weak tunneling and flat tunneling functions combined. For a structure, whose tunneling functions have a complex sd spectral structure, and are moderately strong, we derive an improved GME using a novel “corrected GKBA” incorporating a stationary approximation to the vertex part of the exact reconstruction equations whose free term is the standard GKBA. Numerical tests are successful.

A not satisfactorily solved problem of relativistic transformation of temperature playing the decisive role in relativistic thermal physics and cosmology is reopened. It is shown that the origin of the so called Mosengeil-Ott's antinomy and other aligned paradoxes are related to the wrong understanding of physical meaning of temperature and application of Planck's Ansatz of Lorentz's invariance of entropy. In the contribution we have thus reintroduced and anew analyzed fundamental concepts of hotness manifold, fixed thermometric points and temperature. Finally, on the basis of phenomenological arguments the Lorentz invariance of temperature and relativistic transformations of entropy are established., Comment: 9 pages

This paper summarizes the recent state of the art of the following topics presented at the FQMT’08 conference: Foundations of quantum physics, Quantum measurement; Quantum noise, decoherence and dephasing; Cold atoms and Bose–Einstein condensation; Physics of quantum computing and information; Nonequilibrium quantum statistical mechanics; Quantum, mesoscopic and partly classical thermodynamics; Mesoscopic, nano-electro-mechanical systems and optomechanical systems; Spins systems and their dynamics, Brownian motion and molecular motors; Physics of biological systems, and Relevant experiments from the nanoscale to the macroscale. To all these subjects an introduction is given and the recent literature is overviewed. The paper contains some 680 references in total.

The simplest nanoscopic system, a molecular bridge consisting of a molecular island with one or few electronic or vibronic levels coupled to non-interacting leads can be treated using non-equilibrium Green's functions (NGF). We follow the well known procedure of Jauho, Wingreen and Meir (JWM). In the present work, we concentrate on the little investigated transient behavior of the molecular bridge undergoing abrupt changes. The transient process depends on the initial conditions at a finite time which may incorporate initial correlations. As an example, we study the electron response to sudden connecting the molecule to one or both leads. To obtain explicit solutions, we neglect all interactions at the island, whose role is mimicked by the island–leads coupling. We explore this analogy and obtain a complete solution for the transient NGF for arbitrary “initial correlations” represented by off-diagonal coherences between the initial electron state of the island and of the leads. This direct one-electron solution is confronted with the field theoretic approach in the particular case of the switch-on states, for which the initial correlations result from the previous history of the system. This is formally captured by the partitioning-in-time of the NGF, which we combine with the JWM theory. It is the virtue of partitioning method to express the transient NGF in terms of the building blocks of stationary-state NGF with zero, one or both leads connected. The direct and the partitioning solutions are reduced explicitly from one to the other, clarifying thus the meaning of the singular terms of the self-energy for correlated initial conditions.

Recent developments in technologies and experiments enable us to observe dynamical behavior of very small quantum systems under conditions when it is sensitive to system parameters, internal interactions, the environment and the external time-dependent fields. This contribution deals with the status and perspectives of description of such truly non-equilibrium quantum many body systems using the non-equilibrium Green's functions (NGF). The basic aim of this approach is to describe time development of the many-body system out of equilibrium from its initial state over its transient dynamics to its long time asymptotic evolution. The early stages of the transient evolution will be characterized for a broad class of the initial conditions generated in the course of Keldysh switch-on states. Gradual loss of initial correlations due to interactions and related renormalization processes in the system may, under favorable conditions, give rise to the evolution stage expressible in terms of non-equilibrium quasi-particles. This permits to reduce the description of the system behavior to a quantum transport equation. The consistency of such approximations for NGF may be judged by checking the non-equilibrium version of transport Ward identities. These identities follow from the gauge invariance of the 1st kind for NGF. To cover the whole time domain of the transient, we obtain the non-equilibrium Ward identities for NGF with initial conditions included.

This contribution presents an alternative approach to thermal physics and to its affiliated thermodynamics aiming to initiate a discussion concerning the related problems of its fundamental nature. We reason that the classical thermodynamics suffers considerably from a misinterpretation of experimental facts known as the Principle of Equivalence of Energy and Heat and from the resulting introduction of a troublesome quantity called entropy lacking clear physical meaning within the traditional thermodynamics. As this concept generates an endless chain of paradoxes connected mainly with the Second Law of Thermodynamics , we propose to change the structure and the conceptual basis of thermal physics prior to the solving of more complex problems involving, e.g., the application of quantum or stochastic electrodynamics to the relativistic thermal phenomena. We argue that a good candidate for such a more satisfactory theory is modified Carnot's theory reintroducing an old–new physical quantity historically named caloric. An introducing outline customizing the reader with the basic ideas of this alternative version of the classical thermodynamics is thus given. Principal relations of the caloric theory are presented, together with illustrative treatment of some common tasks of the thermal physics. Use of the caloric theory to description of real heat engines is also presented.

This paper summarizes the present views on construction of the electron quantum transport equations based on the Non-Equilibrium Green's Functions approach. The basic tool is the so-called Ansatz decoupling; one Ansatz family stems from the original Kadanoff-Baym Ansatz and is suitable for extending the quasi-particle picture of the Landau theory out of equilibrium. The other family based on the Generalized KB Ansatz is appropriate for short time transients. The physical and formal context of the Ansatzes is analyzed; the most important question explored is the status of the Reconstruction Theorems, reducing a full description of a non-equilibrium system to a dynamic theory in terms of one-particle quantities. A comparison is made between the Time Dependent Density Functional Theory and the properly renormalized NGF formalism. There is a close relationship between both formalisms. The Reconstruction Theorems form a general basis for obtaining improved quantum transport equations.

The quantum transport equations for fast transients have the structure of a Generalized Master Equations for the single-particle distribution, with causal memory terms. Nonequilibrium Green’s functions are reduced to GME if the Generalized Kadanoff–Baym Ansatz is applied. This Ansatz has been used with success both to non-linear transport and to optical transients in semi-conductors; further progress is linked with its extension to a family of the Causal Ansatzes, differing primarily in renormalization of the propagators. For the switch-on non-equilibrium states, generated by a perturbation from equilibrium, the renormalization to the dark dressed Green’s function followed by calculation of the induced self-energies is a productive direction. It also circumvents the problem of correlated initial conditions, far from a general solution otherwise. Such initial conditions appear as incompatible with a Causal Ansatz in general. The presently available formalism permits to study a transient process in the whole time range using the complete NGF, but making a flexible Ansatz-based reduction appropriate to the stage of dynamic evolution. r 2005 Elsevier B.V. All rights reserved.

Non-equilibrium Green's functions reduce to quantum kinetic equations in the kinetic regime, that is, if the quasi-classical, quasi-particle picture is valid. The classical tool yielding the kinetic equations, the Kadanoff–Baym Ansatz, has been improved and generalized to a whole Ansatz family including the so-called extended quasi-particle approximation. Each Ansatz produces a quantum kinetic theory: a quasi-particle kinetic equation and a functional of the quasi-particle distribution returning the average values of observables. In the extended quasi-particle model, the theory is physically consistent: causal, gauge invariant and conserving. This model leads to kinetic equations for dense Fermi liquids which combine the Landau quasi-particle drift with non-local scattering integrals in the spirit of the Enskog equation.

In the present contribution we analyse, within the frame of a particular form of classical electrodynamics, a simple thought experiment performed by an idealized heat engine bathed in zero-point (ZP) electromagnetic radiation. In contrast to the usual forms of heat engines driven by electromagnetic radiation, all partitions of our engine are made of more realistic material having an upper frequency cut-off. Analysing the operation of such an engine at T = 0 , a possible mechanism of filling real cavities with ZP radiation based on Doppler's effect has been suggested.

This paper summarizes the recent state of the art of the following topics presented at the FQMT'04 conference: Quantum, mesoscopic and (partly) classical thermodynamics; Quantum limits to the second law of thermodynamics; Quantum measurement; Quantum decoherence and dephasing; Mesoscopic and nano-electro-mechanical systems; Classical molecular motors, ratchet systems and rectified motion; Quantum Brownian motion and Quantum motors; Physics of quantum computing; and Relevant experiments from the nanoscale to the macroscale. To all these subjects an introduction is given and the recent literature is broadly overviewed. The paper contains some 450 references in total., 31 pages, 455 references with titles

The subject of this paper is the long-lasting controversy on the relativistic transformation of temperature, generally known as the Planck-Ott imbroglio. Various, mostly unsuccessful, attempts to solve this demanding problem using a combinations of tools of classical thermodynamics, transformation rules of special theory of relativity, theory of black-body radiation and kinetic theory, are reviewed. Using phenomenological analysis, we demonstrate that the failure of these attempts and the existence of the imbroglio itself are most likely due to the misunderstanding of the physical meaning of temperature and to some serious flaws in foundations of classical thermodynamics. We further show that the temperature of a moving body must remain invariant for observers in all relatively moving frames.

The Non-Equilibrium Fluctuation-Dissipation Theorem (NE FDT) is formulated within the Non-Equilibrium Green Function (NEGF) formalism. The relation of this theorem to a simplified kinetic theory of non-equilibrium dynamics of electrons in open quantum systems is discussed. The possibility of such a simplified description is first discussed on non-equilibrium dynamics of the molecular bridge model represented by calculations of transient magnetic currents between two ferromagnetic electrodes linked by tunneling junctions to a molecular size island of an Anderson local center type. This model can be treated by using the full set of equations for NEGF, which can be solved numerically. This provides a reference framework for testing the possibility of a simpler and physically more transparent solution based on a Non-Markovian Generalized Master Equation (GME) as an approximation of the full set of NEGF equations. The advantages and limitations of the use of the Generalized Kadanoff-Baym Ansatz (GKBA) for this simplified description is demonstrated. The basic question is the range of applicability of this approximation. It turns out that for our specific model the decisive feature is the spectral structure of the tunneling functions of both electrodes and their positioning with respect to the island level depending on the bias and the exchange splitting. Finally, the relation of this simplified description to non-equilibrium generalization of FDT is shown independently on the chosen model. The connection between the NEGF reconstruction equations and the non-equilibrium version of FDT is introduced and the possible approximations of this general scheme are discussed.

Kerr-Newman Electron as Spinning Soliton (Alexander Burinskii) Elements For the Development of A Darwinian-Like Scheme Leading to Quantum Mechanics (Carlos Baladron) A Geometrical Approach to Dislocation Densities in Semiconductors (K Bakke and F Moraes) The Zero-Point Field and the Emergence of the Quantum (L De La Pena, A M Cetto and A Valdes Hernandez) Emergence of Quantum Mechanics From Sub-Quantum Statistical Mechanics (Gerhard Grossing) Towards Wave Resolution of Wave-Particle Duality (Andrei Khrennikov) Quantum Transport: An Unified Approach Via A Multivariate Hypergeometric Generating Function (A F Macedo-Junior and A M S Macedo) Time-Dependent Coupled Harmonic Oscillators: Classical and Quantum Solutions (D X Macedo and I Guedes) Event-Based Simulation of Quantum Physics Experiments (Kristel Michielsen and Hans De Raedt) Lectures on Dynamical Models For Quantum Measurements (T M Nieuwenhuizen, M Perarnau Llobet and R Balian) Physics of Quantum Computing (Elisabetta Paladino and Giuseppe Falci) Reality, Causality, and Probability, From Quantum Mechanics to Quantum Field Theory: Lectures on the Epistemology of Quantum Theory (Arkady Plotnitsky) Quantum Information in Communication and Imaging (David Simon, Gregg Jaeger and Alexander V Sergienko) Green's Function Technics in the Solid State (Vaclav Spicka)

The finite duration of the collisions in Fermionic systems as expressed by the retardation time in non-Markovian Levinson-type kinetic equations is discussed in the quasiclassical limit. We separate individual contributions included in the memory effect resulting in (i) off-shell tails of the Wigner distribution, (ii) renormalization of scattering rates and (iii) of the single-particle energy, (iv) collision delay and (v) related non-local corrections to the scattering integral. In this way we transform the Levinson equation into the Landau-Silin equation extended by the non-local corrections known from the theory of dense gases. The derived nonlocal kinetic equation unifies the Landau theory of quasiparticle transport with the classical kinetic theory of dense gases. The space-time symmetry is discussed versus particle-hole symmetry and a solution is proposed which transforms these two exclusive pictures into each other., slightly revised, 19 pages

After the short time regime the time evolution is controlled by small gradients. This leads to a nonlocal Boltzmann equation for the quasiparticle distribution and a functional relating the latter one to the reduced density matrix. The nonlocalities are presented as time and space shifts arising from gradient expansion and are leading to virial corrections in equilibrium.

The formation of correlations due to collisions in an interacting Fermionic system is investigated. We present analytically the time dependent interaction energy with and without initial correlation. This short time behavior is characterized by the reduced density matrix possessing high energetic tails.

A current induced by the van der Waals interaction between two parallel two-dimensional metals is reinterpreted in the quasiparticle picture. It is shown that in the presence of a dissipation, this current vanishes due to an effect of the van der Waals interaction on scattering processes.

Phenomenologic description of the two-stream instability in two parallel two-dimensional (2D) metals is derived. The frequency and rate of growth of an instable mode is expressed in terms of frequencies and damping of plasma waves in isolated 2D metals. These input parameters are experimentally accessible, e.g., by the far-infrared spectroscopy or by the Raman scattering. The presented theory indicates that a system with one metal driven and the second one kept under the zero current condition is more promising for the instability than two metals driven in the opposite directions.

Virial corrections to the Boltzmann equation for quasiparticles are obtained from non-equilibrium Green's functions. These corrections are expressed in terms of shifts in space and time that characterize non-locality of scattering integrals. The space shifts parallel finite-diameter corrections to collisions of hard spheres. The time shift is identified as the collision delay. All shifts are given by derivatives of the phase shift in a binary collision.

The formation of binary correlations in plasma is studied from the quantum kinetic equation. It is shown that this formation is much faster than dissipation due to collisions. In a hot (dense) plasma the correlations are formed on the scale of inverse plasma frequency (Fermi energy). We derive analytical formulae for the time dependency of the potential energy which measures the extent of correlations. We discuss the dynamical formation of screening and compare with the statical screened result. Comparisons are made with molecular dynamic simulations.

This paper deals with the recent state of the art of the following topics presented at the FQMT’11 conference: foundations of quantum physics, quantum measurement; nonequilibrium quantum statistical physics; quantum thermodynamics; quantum measurement, entanglement and coherence; dissipation, dephasing, noise, and decoherence; quantum optics; macroscopic quantum behavior; e.g. cold atoms; Bose-Einstein condensates; physics of quantum computing and quantum information; mesoscopic, nano-electro-mechanical systems and nano-optical systems; spin systems and their dynamics; biological systems and molecular motors; and cosmology, gravitation and astrophysics. The lectures and discussions at the FQMT’11 conference, as well as the contributions to the relatedtopical issue, reveal important themes for future development. The recent literature is included.

The quasiparticle approximation and corrections beyond it are derived from expansion in the spirit of the virial corrections. This way, the Boltzmann equation for electrons in semiconductors is recovered from the nonequilibrium Green's functions without unjustified neglect of the former theory. The present approach gives higher-order contributions to the scattering rates and provides observables as functionals of the quasiparticle distribution. The application scheme is of the same simplicity as the one based on the quasiparticle approximation. Five applications to phenomena beyond the scope of the quasiparticle approximation are presented: two-phonon scattering rates, compensation of wave-function remormalization for isotropic elastic scattering, quasiparticle backflow, backflow current of waves, and discussion of the collisional broadening.

We study fast transient dynamics of an open quantum system at the initial stage of its equilibration starting far from equilibrium from correlated initial conditions reflecting entanglement with the environment. These correlations rapidly decay and the process enters the non‐equilibrium quasi‐particle mode controlled by a generalized master equation. As a model system, the nanoscopic molecular bridge between two leads is considered. The coupling to the leads is assumed to be intermittent. Properties of the resulting transients are demonstrated and analyzed.

Study of transients in the electron quantum transport by nonequilibrium Green's function often requires an explicit inclusion of correlations at a finite initial time. For processes embedded in a host process, a universal treatment of the correlated initial conditions based on the formalism of partitioning in time allows to express their self-energy including the ``irregular'' correlation part in terms of the known properties of the host process. This unified formalism also yields the renormalized semigroup property for propagators and the reconstruction equations for the particle correlation function. The Bogolyubov principle of the decay of correlations then permits to buildup a theory of quantum transport equations with finite-time initial conditions.

This paper investigates the question whether a realistic black hole can be in principal similar to a star, having a large but finite redshift at its horizon. If matter spreads throughout the interior of a supermassive black hole with mass $M\sim10^9M_\odot$, it has an average density comparable to air and it may arise from a Bose-Einstein condensate of densely packed H-atoms. Within the Relativistic Theory of Gravitation with a positive cosmological constant, a bosonic quantum field describing H atoms is coupled to the curvature scalar with dimensionless coupling $\xi$. In the Bose-Einstein condensed groundstate an exact, self-consistent solution for the metric occurs for a certain large value of $\xi$, quadratic in the black hole mass. It is put forward that $\xi$ is set by proper choice of the background metric as a first step of a renormalization approach, while otherwise the non-linearities are small. The black hole has a hair, the binding energy. Fluctuations about the ground state are considered., Comment: 18 pages Latex Physica E style

A nonequilibrium Ward identity (NE WI) connecting the scalar transport vertex correction with one-particle self-energy is derived using the global $\mathrm{U}(1)$ symmetry of the fermion nonequilibrium Green's functions (NGF). The nonperturbative derivation does not depend on the details of the many-body system. A renormalized multiplicative composition rule for the NGF, reflecting time coherence, is obtained and related to the NE WI. Applications involve (i) testing the consistency of approximations shown in the example of a self-consistent Born approximation for disorder scattering, and (ii) in the general quantum transport theory, the formalism permits one to assess routes to generalized master equations, in particular those based on the generalized Kadanoff-Baym ansatz.

The formation of binary correlations in plasma is studied from the quantum kinetic equation. It is shown that this formation is much faster than dissipation due to collisions. In a hot (dense) plasma the correlations are formed on the scale of inverse plasma frequency (Fermi energy). We derive analytical formulae for the time dependency of the potential energy which measures the extent of correlations. We discuss the dynamical formation of screening and compare with the statical screened result. Comparisons are made with molecular dynamic simulations., Proceedings of the 8th International Workshop on Atomic Physics for Ion-Driven Fusion, Heidelberg 1997, appear in Laser and Particle Beams

In the present contribution a simple thought experiment made with an idealized spherical enclosure bathed in zero-point (ZP) electromagnetic radiation and having walls made of a material with an upper frequency cut-off has been qualitatively analysed. As a result, a possible mechanism of filling real cavities with ZP radiation based on Doppler's effect has been suggested and corresponding entropy changes have been discussed.

The characteristic time of formation of correlations at high temperature limit is given by the inverse plasma frequency \( \tau _C \approx \frac{1} {{\omega _p }} = \frac{{\sqrt 2 }} {{\upsilon _{th} \kappa }} \) . The inverse plasma frequency indicates that the dominant role play the long range fluctuation. On the other hand, we also see that the correlation time is found to be given by the time a particle needs to travel through the range of the potential with a thermal velocity υth. This confirms the numerical finding of [12] that the correlation or memory time is proportional to the range of interaction. In the low temperature region, i.e., in highly degenerated system μ 》 T one finds a differentpicture. From (3) we can calculate the formationofcorrelationsaswell. 13,14 Unlike in the classical case, the equilibrium limit of the degenerated case is rapidly built up and then oscillates around the equilibrium value. We can define the build up time τ C as the time where the correlation energy reaches its first maximum, \( \tau _C = 1.0\frac{\hbar } {\mu } \) . Note that τ C is in agreement with the quasiparticle formation time known as Landau’s criterion for is the Fermi energy. Indeed, the quasiparticle formation and the build up of correlations are two alternative views of the same phenomena. The formation of binary correlations is very fast on the time scale of dissipative process. Under extremely fast external perturbations, like the massive femto second laser pulses, the dynamics of binary correlations will hopefully become experimentally accessible. Even if related measurement will not reveal any unexpected features, the experimental justification of basic concepts of the non-equilibrium many-body physics is very desirable.

This paper extends our recent theoretical study of transient currents in molecular bridge junctions [1] to magnetic tunneling. Presently, we calculate the excess magnetic tunneling through the molecular bridge shunting the junction. The system is represented by two ferromagnetic electrodes bridged by a molecular size island with one electronic level and a local Hubbard type correlation. The island is linked with the electrodes by tunneling junctions whose coupling strength is assumed to undergo rapid changes affecting the connectivity of the system. We employ the non-equilibrium Green’s functions. The numerical solution is obtained solving the real-time Dyson equation in the integro-differential form self-consistently. The switching events controlling the junctions give rise to transient changes of magnetisation of the island. They strongly depend on the static galvanic bias between the electrodes, mutual alignment of their magnetisation and on the time scale of the switching.

The short time behavior of a disturbed system is influenced by off-shell motion and best characterized by the reduced density matrix possessing high energetic tails. We present analytically the formation of correlations due to collisions in an interacting Fermionic system with and without initial correlation. After this short time regime the time evolution is controlled by small gradients. This leads to a nonlocal Boltzmann equation for the quasiparticle distribution and a functional relating the latter one to the reduced density matrix. The nonlocalities are presented as time and space shifts arising from gradient expansion and are leading to virial corrections in the thermodynamical limit., Comment: Proceedings KB99 Workshop, September 20-24 1999, Rostock, Germany

The damping of hot giant dipole resonances is investigated. The contribution of surface scattering is compared with the contribution from interparticle collisions. A unified response function is presented which includes surface damping as well as collisional damping. The surface damping enters the response via the Lyapunov exponent and the collisional damping via the relaxation time. The former is calculated for different shape deformations of quadrupole and octupole type. The surface as well as the collisional contribution each reproduce almost the experimental value, therefore we propose a proper weighting between both contributions related to their relative occurrence due to collision frequencies between particles and of particles with the surface. We find that for low and high temperatures the collisional contribution dominates whereas the surface damping is dominant around the temperatures $\sqrt{3}/2\pi$ of the centroid energy., Comment: PRC sub