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The quality of the transient electricity is disturbed by the switching of the capacitor banks steps, thus affecting the equipment of the related electrical installation. The transitional regime may be defined as the variable mode of transition from an initial state of operation (a permanent regime) to another permanent regime. The transitional regime is generally a short-term one due to the short time constants of the electrical grids, but which may affect the security of electrical installations or the stability of their operation. Transitional phenomena resulting from the switching of capacitor banks are becoming more and more important, as the number of capacitor banks in the supply systems increases. This is because the most common operation is the capacitor banks switching, which can occur several times a day depending on the need of the reactive power/energy to stabilize voltage and maintain power factor in admissible limits. This paper analyzes, using EMTP software, the impact of capacitor transients for different scenarios and with different methods of mitigating the quality of electricity.

The paper presents methods and techniques for monitoring the status and diagnosis of wear for each element in the architecture and operation of photovoltaic solar power plant. A typical configuration of photovoltaic solar power plant is: photovoltaic panel, junction box, connection cables, controller, battery and inverter. The first part of this study describes the methods and techniques often used in monitoring and diagnosing the state of a system. In the second part of the study is presented a new method and technique used in monitoring and diagnosing the state of a system, SMART FMECA. This new method will help to approach a better hierarchy of each failure mode, for each component.

The paper presents the failure modes, the effects and the criticality for each element in the architecture and operation of a photovoltaic system. A typical configuration is considered: photovoltaic panel, junction box, connection cables, controller, battery and inverter. The first part of this study generally describes the current state of the failure modes and effects for each element of the photovoltaic system. In the second part of the study is presented a structured case study based on the LACARP photovoltaic system that is part of LACARP’s laboratory of Faculty of Electrical Engineering of the “Gheorghe Asachi” Technical University of Iasi including customized criteria and indicators for each element of a photovoltaic system. This approach will help establishing the hierarchy and the integration of each failure mode and the level of rated power affected.

The integration of energy from renewable sources has become a topic of interest. The most used sources with a high energy potential are photovoltaic sources. Thus, in order to use the photovoltaic energy with a higher efficiency, the methods of traditional load management are involved in residential sector in order to ensure an optimal balance between demanded load and generated power. Considering these issues, the paper presents a SIoTEM system developed to manage the thermal appliances of a residential customer in order to minimize the amount of energy exchanged with the electrical grid.

The power quality in industry is actually of a greater importance due to the presence of sensitive loads like computers, protection relays, measurement and other electronic devices operated near the high-power nonlinear loads. One of the most important aspects of this quality is related to the harmonic distortion of voltage and current waves with the well-known negative consequences on the industrial power system components and its operating efficiency. This paper analyses the effects on the quality of electrical energy of the multipulse rectifiers used to supply some electrical high-power drives as main components of the production process, involved in the driving of the rolls of the scraper from a hot strip mill. The measurement results show clearly the advantage of the presence of the 6-pulse and 12-pulse rectifiers during the fast transient conditions of slab lamination.

Different maintenance methods are used in industry. The classic preventive planned one is mainly replaced by the preventive opportune type. The second is based on state condition monitoring of different power systems components. Unfortunately it is expensive and only in few cases are technically and economically justified. This paper present a technique to evaluate the maintenance policy efficiency and, finally to rank the subsytems of high voltage circuit-breakers aiming to select what subsystem can be selected for state monitoring. A large database for 12 circuit-breakers was used and the information about failures and maintenance during 33 years was used for analysis.

In this work we study an effective three-mode model describing interacting bosons. These bosons can be considered as exciton-polaritons in a semiconductor microcavity at the magic angle. This model exhibits quantum phase transition (QPT) when the parameters of the corresponding Hamiltonian are continuously varied. The properties of the Hamiltonian spectrum (e.g., the distance between two adjacent energy levels) and the phase space structure of the thermodynamic limit of the model are used to indicate QPT. The relation between spectral properties of the Hamiltonian and the corresponding classical frame of the thermodynamic limit of the model is established as indicative of QPT . The average number of bosons in a specific mode and the entanglement properties of the ground state as functions of the parameters are used to characterize the order of the transition and also to construct a phase diagram. Finally, we verify our results for experimental data obtained for a setting of exciton-polaritons in a semiconductor microcavity., Comment: 22 pages, 13 figures. Published with minor changes in Phys. Rev. E vol. 96, No. 6, 062146 (2017)

Light flicker (LF) phenomenon represented a concern for the researchers for several decades and is still considered one of the most important power quality problems due to its ability to be directly perceived by human beings causing significant physiological discomfort, physical and psychological tiredness, and even pathological effects. More than that, light flicker can trigger headaches, migraines, fatigue, epilepsy, and other neurological responses. The aim of this paper is to present a method for collecting the waveforms corresponding to the luminous flux modulation for different light sources using a high speed camera. The light flicker presence detection as well as its frequency are characterized based on the obtained waveforms plots using FFT techniques.

We illustrate the equivalence between the non-unitary evolution of an open quantum system governed by a Markovian master equation and a process of continuous measurements involving this system. We investigate a system of two coupled modes, only one of them interacting with external degrees of freedom, represented, in the first case, by a finite number of harmonic oscillators, and, in the second, by a sequence of atoms where each one interacts with a single mode during a limited time. Two distinct regimes appear, one of them corresponding to a Zeno-like behavior in the limit of large dissipation.

We model a feasible experiment involving two interacting microwave cavities with very different quality factors. An excitation is initially present in the high Q cavity. Modeling the environment as linearly coupled oscillators, we find a Zeno-like behavior which should occur when the dissipation constant is large enough as compared to the unitary coupling.

We develop a protocol based on 2M pairwise-interacting qubits, which through the quantum Zeno effect controls the entanglement distribution of the system. We present two examples: the first is concerned with the well-known double Jaynes–Cummings model, and in the second we construct a generalization for 2M qubits coupled pairwise. This provides a way of data manipulation within a quantum register which allows the transfer of data between qubits without the physical movement of any of the qubits.

We present a rigorous, regularization independent local quantum field theoretic treatment of the Casimir effect for a quantum scalar field of mass $\mu\ne0$ which yields closed form expressions for the energy density and pressure. As an application we show that there exist special states of the quantum field at fixed cosmic time, in which the expectation value of the renormalized energy-momentum tensor is independent of the space coordinate and is of the perfect fluid form $g_{\mu,\nu}\rho_{vac}$ with $\rho_{vac}>0$, thus providing a quantum field theoretic foundation of the Cosmological constant. Using some values of $\mu$ suggested in the literature for the hypothetical axion particle, there results a model for dark energy which is consistent with past and future evolution and is also in good agreement with experimental data., Comment: 15 pages, 2 figures, conceptually improved version, to appear in Ann. Phys

The “time reversal” dynamics of dissipative atom-cavity systems has been recently experimentally investigated. We model the experimental procedure using semiclassical approximations which allow for analytical results and to distinguish decoherence from damping effects. We show that the basic effect of decoherence is to drastically alter the envelope of the population inversion, mainly the amplitude. Damping, on the other hand, is responsible for the anticipation of the revival times and corrections to the fast frequencies in each envelope.

The dissipative dynamics of Gaussian squeezed states (GSS) and coherent superposition states (CSS) are analytically obtained and compared. Time scales for sustaining different quantum properties such as squeezing, negativity of the Wigner function or photon number distribution are calculated. Some of these characteristic times also depend on initial conditions. For example, in the particular case of squeezing, we find that while the squeezing of CSS is only visible for small enough values of the field intensity, in GSS it is independent of this quantity, which may be experimentally advantageous. The asymptotic dynamics however is quite similar as revealed by the time evolution of the fidelity between states of the two classes., Accepted version

In this paper we investigate how common is the phenomenon of Finite Time Disentanglement (FTD) with respect to the set of quantum dynamics of bipartite quantum states with finite dimensional Hilbert spaces. Considering a quantum dynamics from a general sense, as just a continuous family of Completely Positive Trace Preserving maps (parametrized by the time variable) acting on the space of the bipartite systems, we conjecture that FTD happens for all dynamics but those when all maps of the family are induced by local unitary operations. We prove this conjecture valid for two important cases: i) when all maps are induced by unitaries; ii) for pairs of qubits, when all maps are unital. Moreover, we prove some general results about unitaries/CPTP maps preserving product/pure states, 7 pages and 2 figures. New title. Improved version! Comments are welcome

We apply implicit regularization in the calculation of the one-loop graviton and gravitino corrections to the anomalous magnetic moment of the lepton in unbroken supergravity. This is an important test for any regularization method. We find a null result as it is expected from supersymmetry. We compare our results with the ones obtained by using differential regularization and dimensional reduction, which are known to preserve supersymmetry at one-loop order.

We present a noise-driven model for obtaining the gap and line-width as functions of the temperature in the nonlinear sigma model. The method is phenomenological and rests on the following physical idea: a classical external stochastic field is introduced representing the coupling of the sigma field with a noise source. Moreover, we assume that the inelastic scattering length is much longer than the elastic one, justifying the neglect of dissipation for temperatures such that the nonlinear sigma model is a good approximation for antiferromagnetic spin chains. This phenomenological approach is justified by comparison with other theoretical predictions and with experiment.

We investigate the conditions for the existence of states less exposed to the environment and decoherence-free subspaces (DFS) for two oscillators subjected to reservoirs at any temperature. We show that the main effect of the temperature is to fasten the decoherence process. However, the DFS found for zero temperature remain protected. A solution for diffusive environments is presented.

A quantum phase transition, characterized by an accumulation of energy levels in the espectrum of the model, is associated with a qualitative change in the corresponding classical dynamic obtained upon generalized coherent states of angular momentum.

The extension of the Caldeira–Leggett model to two oscillators coupled to a reservoir predicts an environment induced interaction between the two oscillators, which may lead to decoherence-free subspaces. A quantitative analysis of the parameter's strength of the model is therefore important. We propose here an experiment capable of deciding this question.

Universidade Federal de Minas Gerais, C.P. 702, 30161-970 Belo Horizonte, M.G., BrazilAbstractThe exact reduced dynamics for the independent oscillator model in the RWA approximation atzero and finite temperatures is derived. It is shown that the information about the interaction and theenvironment is encapsulated into three time dependent coefficients of the master equation, one of whichvanishes in the zero temperature case. In currently used optical cavities all the information about thefield dynamics is contained into two (or three) experimentally accesible and physically meaningful realfunctions of time. From the phenomenological point of view it suffices then to carefully measure two(three) adequate observables in order to map the evolution of any initial condition, as shown with severalexamples: (generalized) coherent states, Fock states, Schr¨odinger cat states, and squeezed states.

From a medical point of view, human suffering due to ergotism has been best and very realistically portrayed in the paintings and drawings of Hieronymus Bosch, Pieter Bruegel the Elder and Mathis Grunewald. These painters have often documented the miserable life of the cripples or other disabled people with the characteristic signs of cerebral palsy or polio. On the altar of Isenheim (in Colmar), Grunewald depicted some victims of ergotism and 14 medical herbs, which are a botanically correct table, and maybe the forgotten ingredients for the Antonite-balsam and -wine. It cannot be excluded with certainty that the existence of psychotropic drugs in medieval times and the experiences of ergotism caused by toxic delirium may be an explanation for the origins of some paintings by H. Bosch, Grunewald and P. Bruegel. D 2002 Elsevier Science B.V. All rights reserved.

We present the Weyl–Wigner (WW) transform theory in a much more compact way than usual, by introducing the Δ basis in an intrinsic form. This permits the derivation of new identities and also leads to generalizations, like the inclusion of finite-dimensional systems in the WW theory, which is also discussed. We show, in this case, some striking differences in the structure of finite phase space depending on the underlying dimension of quantum space being an even or odd integer.

Effects of dissipation during the interaction of two-level atoms with a single mode of the electromagnetic field are considered in the context of the dispersive Jaynes–Cummings model to which a damping mechanism is added. The results are applied to the analysis of the so-called Paris experiment (Brune M et al 1996 Phys. Rev. Lett. 77 4887). We obtain analytical expressions for the conditional probabilities measured in this experiment considering the dissipation during the atom–field interaction in both preparing and monitoring stages of the 'Schrodinger cat' state. We show that during the formation of the superposition state decoherence results from a competition between the atom–field (unitary) and field–cavity (dissipative) interactions. Moreover, it is quantitatively comparable to the purity loss expected for the field evolving freely during a time interval equal the interaction time. These effects are dominant at short time scales. For later times, the measured conditional probabilities reflect decoherence effects arising from field–cavity interactions.

We derive the tunneling rate for paramagnetic molecules in the context of a collective spin model. By means of path integral methods an analytical expression is derived. Given the very large spins in question (s ~ 3000 hbar), the observation of magnetization changes due to pure unitary tunnel effects is unlikely., Comment: 16 pages, 2 figures

We describe in detail how a sliding scale is introduced in the renormalization of a QFT according to integer-dimensional implicit regularization scheme. We show that since no regulator needs to be specified at intermediate steps of the calculation, the introduction of a mass scale is a direct consequence of a set of renormalization conditions. As an illustration the one-loop β-function for QED and λϕ4 theories are derived. They are given in terms of derivatives of appropriately systematized functions (related to definite parts of the amplitudes) with respect to a mass scale μ. Our formal scheme can be easily generalized for higher loop calculations.

We investigate the relationship between orbital instability and decoherence in de Sitter (dS) spacetime. We consider a simple quadratic toy model proposed by Brandenberger, Laflamme and Miji\ifmmode \acute{c}\else \'{c}\fi{} of two interacting scalar fields in a dS background. It admits a modewise separation, with each mode consisting of a pair of nonautonomous coupled harmonic oscillators. We show that the (classical) maximal Lyapunov exponent of every mode equals the asymptotic rate of (quantum) von Neumann entropy production of each oscillator, assuming an initial vacuum. We find that for moderately long times after horizon crossing, orbital instability, entropy and single-mode squeezing are larger for increasing coupling strength. If the entropy of an oscillator increases more rapidly than squeezing, for example in the strong-coupling regime for not too high frequencies, the noise of every quadrature of the asymptotic state will be larger than the vacuum noise. The results suggest the possibility that simple, nonlinear interacting physical processes with unstable or chaotic classical counterparts may provide an important contribution to the effectiveness of the classicalization of cosmological scalar fields during a dS stage of spacetime expansion.

In two-dimensional systems, predictability and visibility satisfy a complementarity relation, which has been generalized to bipartite systems by including the concurrence. We consider systems in which the two alternatives of a which-state experiment are nonorthogonal states and propose generalized measures of predictability and visibility. Criteria like symmetry under exchange of the alternatives, vanishing visibility when only one of the alternatives is present, and clear operational meaning, favor definitions of predictability and visibility which use a three-dimensional basis, previously employed in the unambiguous discrimination of nonorthogonal states. We derive generalized single-partite and bipartite complementarity relations and find that predictability and visibility do not exhaust the single-partite properties for a nonorthogonal basis. A recent experiment on the quantum-classical border is analyzed using generalized complementarity relations.

The authors define the power components under sinusoidal and unbalanced conditions in three-phase, 4-wires circuits proposed as: dissymmetry power S-, and asymmetry power S 0 as components of total unbalanced power S unbalanced due to negative and zero currents components. The physical meaning of the power losses in unbalanced regimes is based on the losses on the neutral wire and on the increased losses in phase conductors due to unbalanced loads compared to balanced situation. A practical and simple algorithm, allowing calculating all specific variables of the unbalanced conditions as well as the power losses is also presented together with the results of a real case study.

In this work we use the formalism of chord functions ( i.e. characteristic functions) to analytically solve quadratic non-autonomous Hamiltonians coupled to a reservoir composed by an infinity set of oscillators, with Gaussian initial state. We analytically obtain a solution for the characteristic function under dissipation, and therefore for the determinant of the covariance matrix and the von Neumann entropy, where the latter is the physical quantity of interest. We study in details two examples that are known to show dynamical squeezing and instability effects: the inverted harmonic oscillator and an oscillator with time dependent frequency. We show that it will appear in both cases a clear competition between instability and dissipation. If the dissipation is small when compared to the instability, the squeezing generation is dominant and one can see an increasing in the von Neumann entropy. When the dissipation is large enough, the dynamical squeezing generation in one of the quadratures is retained, thence the growth in the von Neumann entropy is contained.

We explore quantum properties of a which-way detector using three versions of an idealized two slit arrangement. First, we derive complementarity relations for the detector; second, we show how the 'experiment' may be altered in such a way that using a single-position measurement on the screen, we can obtain quantum erasure. Finally, we show how to construct a superposition of 'wave' and 'particle' components.

We consider a many-body system consisting of a harmonic oscillator linearly coupled to $N$ others and solve the corresponding dynamical problem analytically. Initially, the main oscillator is prepared in a superposition of two coherent states and the $N$ others in the ground states. We divide this system in arbitrary three partitions and the entanglement dynamics between any of these partitions is quantified. We show that the residual entanglement of the tripartite system is always present. Besides, the concurrence of any two partitions depends on the overlap between the two coherent states forming the initial superposition of the main oscillator and the distribution of excitations in the partitions. Finally, we obtain a hierarchy of entanglement between the central oscillator and partitions formed by the other oscillators. For long times the excitations of the main oscillator are completely transferred to the $N$ others and these are found entangled.

Feynman's functional formulation of statistical mechanics is used to study the renormalizability of the well known Linear Chiral Sigma Model in the presence of fermionic fields at finite temperature in an alternative way. It is shown that the renormalization conditions coincide with those of the zero temperature model., Comment: 12 pages, no figures, LaTex, reference [17] is updated, to appear in Phys. Lett. B

The dynamics of the composition of uniform Bose condensates involving two species capable of reciprocal interconversion is treated in terms of a collective quasi-spin model. This collective model quickly reduces to classical form towards the thermodynamic limit. Quantum solutions are easily obtained numerically short of this limit which give insight into the dynamically relevant correlation processes.

The Morse potential is used to obtain analytical solutions of the lowest stationary states of the H2 and HCl molecules. We construct the Husimi distributions for several states and show that the phase space distribution of these states retain several features of its classical limit. Similar results have been reported for one dimensional systems. For the specific case of the central potentials, we show how to treat the angular variables in a consistent way.

We show that the well-known geometric phase, the Gouy phase in optics can be defined for matter waves in vacuum as well. In particular we show that the underlying physics for the “matter waves” Gouy phase is the generalized Schrodinger–Robertson uncertainty principle, more specifically, the off diagonal elements of the covariance matrix. Recent experiments involving the diffraction of fullerene molecules and the uncertainty principle are shown to be quantitatively consistent with the existence of a Gouy phase for matter waves.

We introduce an alternative nonperturbative method to the master equation formalism of describing the evolution of coupled linear systems. The method utilizes the spectral distribution of the normal modes of the complete system to calculate the evolution of the dynamical variables. The dynamical evolution of the Wigner function for a Schrodinger cat state in a damped cavity is considered as example.

A statistical approach to study the escape of an ensemble of particles from classical chaotic systems is proposed. The universal kinetic decay laws, exponential and algebraic, are found through the velocity angle distribution and shown to be specific of distinct motion regimes in the billiards with a small opening. On the basis of the particular case of the dispersing Sinai billiard the escape probability is given in explicit form and the temporal and geometrical conditions are enunciated to make controlled observations of decay dynamics in numerical experiments.

We show that rapid decoherence, usually associated with chaotic dynamics, is not necessarily a hallmark of nonintegrability: border effects in integrable systems may produce similarly drastic decoherence rates. These can be found when the subsystem under observation possesses an energy limitation as, e.g., in the N-atom Jaynes-Cummings model. We show for this model that special initial coherent wave packets exhibit entropy production rates strikingly similar to the chaotic case. Also, a ~de!localization phenomenon is found to be a function of the proximity to the phase-space border. @S1063-651X~99!01611-6# PACS number~s!: 05.45.Mt, 32.80.Qk The quantum entanglement process, decoherence, and the quantum $ classical transition @1# have recently attracted much attention from physicists, both theoretical and experimental @2#. Creating entangled quantum states in the laboratory is now possible in ion trap experiments @3# and also with atoms in high-Q cavities @4#. Both of them realize a simple situation in which a two-level atom is coupled to a quantized harmonic oscillator by means of the Jaynes-Cummings model ~JCM !@ 5 # .This simple model has a long and frequent history as a convenient laboratory for testing theoretical predictions @6#, being expected nowadays to serve also in practical implementations. The physics of this kind of system, where two or more atomic levels interact with a single-mode electromagnetic field, is usually explored by means of quantities such as the population inversion and the mean number of photons. These quantities revealed, among other phenomena, the existence of collapse and revival regions in the curves of population inversion @6,7#. One could then infer that the field and atom lose their identity in the collapse region, and most closely return to their initial states during the revival. However, if one is concerned with the entanglement of the atomic and fieldsubsystems, the population inversion can be a misleading quantity, particularly with respect to the purity of the quantum state. In fact, the works of Phoenix and Knight @8# and that of Gea-Banacloche @9# have shown that this system may greatly recover its purity during the very collapse interval, at half the revival time. In these papers, instead of population inversions, reduced density operators were used in calculating either the system’s entropy or idempotency defect ~linear entropy!. Here we are interested in the decoherence process of systems constituted by subsystems with dissimilar Hilbert spaces. To this end, we take the N-atom JCM, where N two-level atoms interact with a single-mode field and, in view of the results just cited, we adopt the idempotency defect as a measure of the entanglement between the atomic subsystem and the field one. We note incidentally that, compared with the entropy, the calculations of the linear entropy are easier and convey essentially the same information. From another point of view, we want to explore the quantum $ classical connection and possible differences in the decoherence process in integrable and nonintegrable situations. For these reasons, we choose conditions which can be mimicked over the classical phase space. At this point a distinction is noteworthy between the here-called ‘‘quasiclassical’’ treatment of the JCM @10#—where one treats the atomic part quantum mechanically and the field one classically— and our ‘‘semiclassical’’ treatment—where the classical limit is taken for both atomic and fieldquantum subsystems. In the latter context, theoretical investigations using several models suggest that systems which are chaotic in the classical limit decohere rapidly @11,12#. This is also true for the N-atom JCM @13# in its nonintegrable version @14#. Moreover, for the specificcase of Ref. @14#, a connection between the entanglement process and the associated classical structures has been investigated. One of the main results of that investigation is the presence of some sensitivity to where in the classical phase space one places the center of the initial quantum coherent wave packets. It is now a well accepted fact that the decoherence rate is larger for chaotic systems than for integrable ones. We argue here that this belief that the fastest decoherence is to be attributed to chaotic regimes can be misleading in some cases. Such a phenomenon is particularly conspicuous when a ~smaller! subsystem under observation has a finite Hilbert space, a ~larger! subsystem coupled to it does not have such a restriction, and the global system is prepared in a state with mean energy larger than the amount allowed for the smaller subsystem. A phase-space description then reveals the presence of a ‘‘border’’ associated with the degrees of freedom of the smaller subsystem. In such a situation, initial conditions that drive the classical motion to the proximities of this border lead to decoherence rates strikingly similar to those of typical chaotic situations, even if the system is completely integrable. Moreover, another interesting phenomenon related to this is shown to occur: the proximity of the border tends to delocalize the wave packet, whereas for times when the dynamical evolution dictates a departure from the border there is a clear tendency to relocalize the wave packet in the sense that it recovers quantum coherence. These results are shown by comparing the classical and quantum description of the N-atom JaynesCummings model, whose experimental realization is feasible in cavity QED setups. We present arguments according to

The consequences of gravitational zero point quantum fluctuations at Planck scale are considered in the QFTs by adopting an effective stochastic model for space-time. A kinematical approach is used instead of the usual dynamical attempts. The physical quantities are associated to an average over such fluctuations. In particular, the fields have their spectral representation modified. The class of representative field is changed for the description of a field theory and the all order correlation functions, including the two-point functions, are cosequently changed. The investigation of the effect upon QFT succeeded in generating a consistent and more regular theory. In such a scheme the ultraviolet divergences are controlled. Although general, the derivation is performed for scalar Fields. The model is shown to be independent of the specific form of a quantum gravitation theory.

We show how nonrelativistic many body techniques can be used to study quantum corrections to the classical limit, in particular to the SU(2) Lipkin model. We show the quantum corrections are essentially of two types: unitary and nonunitary. In this work we perform a detailed study of the unitary corrections. They can be cast in Hamiltonian form and are shown to double the dimension of the effective phase space. As a consequence chaotic behavior emerges. We show that this semiquantal chaos incorporates the Heisenberg uncertainty principle and thus, is the mechanism through which quantum tunneling is effected. We also show that these corrections systematically improve the classical results and propose some quantitative measure of this improvement.

We show that two-atom correlation measurements of the type involved in a recent experimental study of the evolution of a mesoscopic superposition state prepared in a definite mode of a high-Q cavity can be used to determine the eigenvalues of the reduced density matrix of the field, provided the assumed dynamical conditions are actually fulfilled to experimental accuracy. These conditions involve i) a purely dispersive coupling of the field to the Rydberg atoms used to manipulate and to monitor the cavity field, and ii) the effective absence of correlations in the ground state of the system consisting of the cavity coupled to the ``reservoir'' which accounts for the decoherence and damping processes. A microscopic calculation at zero temperature is performed and compared to master equation results., quantum physics

We revisit the constraints on the coefficients of a quantum Markovian equation recently obtained by Dekker and Valsakumar. We extend these criteria for time-dependent coefficients and establish further criteria where appropriate phenomenological behaviour is required such as dissipation and a Boltzmann asymptotic equilibrium state.

From the study of well-known divergent amplitudes we deduce three consistency conditions which are necessary and sufficient to eliminate ambiguities and symmetry violations. The conditions relate divergent integrals of the same degree of divergence and are automatically satisfied within the context of dimensional regularization. We show how the deduced consistency conditions can be satisfied in four-dimensional regularizations. An important conclusion of the present study is the possibility of working with 4-D regularization schemes which preserve the virtues of dimensional regularization avoiding, however, its restrictions.

Manifestation of chaotic behavior is found in an intrinsically quantum property. The entanglement process, quantitatively expressed in terms of the reduced density linear entropy, is studied for the $N$-atom Jaynes-Cummings model. For a given energy, initial conditions are prepared as minimum uncertainty wave packets centered at regular and chaotic regions of the classical phase space. We find for short times a faster increase in decoherence for the chaotic initial conditions as compared to regular ones, which have oscillatory increase.

The coherent manipulation of the atomic matter waves is of great interest both in science and technology. In order to study how an atom optic device alters the coherence of an atomic beam, we consider the quantum lens proposed by Averbukh et al [1] to show the discrete nature of the electromagnetic field. We extend the analysis of this quantum lens to the study of another essentially quantum property present in the focusing process, i.e., the atom-field entanglement, and show how the initial atomic coherence and purity are affected by the entanglement. The dynamics of this process is obtained in closed form. We calculate the beam quality factor and the trace of the square of the reduced density matrix as a function of the average photon number in order to analyze the coherence and purity of the atomic beam during the focusing process., Comment: 10 pages, 4 figures

We derive the classical limit of the nonintegrable Maser model as a unitary approximation to the exact dynamical evolution of quantum subsystems. We next construct a short time expansion of the evolution of quantum correlations and extract analytical information from the physics which dictates the characteristic time of validity of the classical approximation. We find the rather surprising result that nonintegrable contributions are essential to produce long-lasting classical states.

We re-investigate the problem of the renormalizability of the chiral fermion meson model on the light of the regularization-independent algebraic method. The present letter is intended as a useful application of a modern technique in theory of current interest for the description of low energy hadron phenomenology. We show that the model is stable under radiative corrections and anomaly free in a regularization-free way without having to resort to the explicit calculation of Feynman diagrams.