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Brazilian Journal of Physics, Volume: 35, Número: 2b, Publicado: 2005
  • Second internatinal workshop dice 2004: contributed papers

    Elze, Hans-Thomas
  • Classical limit of non-integrable systems

    Castagnino, Mario

    Resumo em Inglês:

    Self-induced decoherence formalism and the corresponding classical limit are extended from quantum integrable systems to non-integrable ones.
  • Nonlinearities in quantum mechanics

    McHarris, Wm. C.

    Resumo em Inglês:

    Many of the paradoxes encountered in the Copenhagen interpretation of quantum mechanics can be shown to have plausible, more logical parallels in terms of nonlinear dynamics and chaos. These include the statistical exponential decay laws, interpretations of Bell's inequalities, spontaneous symmetry breaking, and perhaps diffractive behavior and even quantization itself. Many of the so-called alternative explanations of quantum mechanics have toyed with ideas that approach chaotic behavior, but as they were formulated before the advent of modern chaos theory, they remained within linear systems or at most nonlinear perturbations to linear systems; however, only strongly nonlinear systems can provide the proper parallels to the Copenhagen paradoxes. Several examples of these will be covered qualitatively. Strongly nonlinear behavior related to quantum mechanics does not involve "hidden variables," but chaos provides a bridge between the statistical behavior of quantum mechanics and deterministic behavior of classical mechanics. Perhaps both Einstein and Bohr were correct in their debates-chaos fundamentally provides the determinism so dear to Einstein, but in practice it must be interpreted statistically in the manner of Bohr.
  • Decoherence of electron waves due to induced charges moving through a nearby resistive material

    Sonnentag, P.; Hasselbach, F.

    Resumo em Inglês:

    An experiment in which decoherence, i.e. the transition from quantum to classical behaviour, can be studied in detail was proposed by Anglin and Zurek [1] and has now been realized. An electron beam in a biprism interferometer is split into two parts both of which travel over a plate made of a highly resistive material at the same, small height. The induced charges inside the plate move along with the beam electron, therefore a current results which encounters ohmic resistance. This process leads to a disturbance in the electron and phonon gas in the plate. As this disturbance is different for the two parts of the beam, entanglement between beam electron and plate is formed. The strength of decoherence, represented by the visibility of the interference fringes, varies as a function of two parameters, the height above the plate and the lateral separation of the beams. Allowing electrons of different height to reach the fluorescent screen successively, 'photos' of the quantum-classical border (continuous decrease of contrast with decreasing height above the plate) are built up.
  • Influence functional approach to decoherence during inflation

    Lombardo, Fernando C.

    Resumo em Inglês:

    We show how the quantum to classical transition of the cosmological fluctuations produced during inflation can be described by means of the influence functional and the master equation. We split the inflaton field into the system-field (long-wavelength modes), and the environment, represented by its own short-wavelength modes. We compute the decoherence times for the system-field modes and compare them with the other time scales of the model.
  • Onset of classical behaviour after a phase transition

    Rivers, R. J.; Lombardo, F. C.

    Resumo em Inglês:

    We analyze the onset of classical behaviour in a scalar field after a continuous phase transition, in which the system-field, the long wavelength order parameter of the model, interacts with an environment of its own shortwavelength modes. We compute the decoherence time for the system-field modes from the master equation and compare it with the other time scales of the model. Within our approximations the decoherence time is in general the smallest dynamical time scale. Demanding diagonalisation of the decoherence functional produces identical results. The inclusion of other environmental fields makes diagonalisation occur even earlier.
  • Cooling many particles to very low temperatures

    Beige, Almut; Knight, Peter L.; Vitiello, Giuseppe

    Resumo em Inglês:

    In a recent paper [Beige, Knight, and Vitiello, quant-ph/0404160], we showed that a large number N of particles can be cooled very efficiently. The particles should be excited by red-detuned laser fields while coupling to the quantized field mode inside a resonant and leaky optical cavity. When the coupling constants are for all particles the same, a collective behavior can be generated and the cooling rate can be as large as << times the single-particle coupling constants. Here we study the algebraic structure of the dynamics and the origin of the collective cooling process in detail.
  • Synchronization of spatially extended chaotic systems with asymmetric coupling

    Boccaletti, S.; Mendoza, C.; Bragard, J.

    Resumo em Inglês:

    In this paper, we report the consequences induced by the presence of asymmetries in the coupling scheme on the synchronization process of a pair of one-dimensional complex fields obeying Complex Ginzburg Landau equations. While synchronization always occurs for large enough coupling strengths, asymmetries have the effect of modifying synchronization thresholds and play a crucial role in selecting the statistical and dynamical properties of the highly coupled synchronized motion. Possible consequences of such asymmetry induced effects in biological and natural systems are discussed.
  • Absorption and emission in the non-poisson case: the theoretical challenge posed by renewal aging

    Aquino, Gerardo; Palatella, Luigi; Grigolini, Paolo

    Resumo em Inglês:

    This short paper aims at clarifying the physical meaning of a previous pubblication [G. Aquino, P. Grigolini, L. Palatella, Phys. Rev. Lett. 93 050601 (2004)], using later, although very recent, results. This has to do with the challenges posed to the Kubo-Anderson (KA) theory, and more in general to any form of Liouville-like approach, by the discovery of intermittent resonant fluorescence with a non-exponential distribution of waiting times. We show that to properly address the treatment of these problems the KA theory, valid in the case of aged systems, should be extended to aging systems, aging for a very extended time period or even forever, being a crucial consequence of non-Poisson statistics. This ambitious goal can be realized if we adopt the assumption that real wave-function collapses occur.
  • Initial states and the various long-time-behaviors of the unstable multilevel systems

    Miyamoto, Manabu

    Resumo em Inglês:

    The decaying behavior of both the survival S(t) and total P(t) probabilities for unstable multilevel systems at long times is investigated by using the N-level Friedrichs model. The long-time asymptotic-forms of both S(t) and P(t) are obtained for an arbitrary initial-state extending over the unstable levels. It is then clarified how the asymptotic forms depend on the initial population in unstable levels. In particular, a special initial state that maximizes the asymptotic form of both S(t) and P(t) is found. On the other hand, the initial states eliminating the first term of their asymptotic expnasions also exist, which implies that a faster decay rather than expected can be realized. This faster decay for S(t) is numerically confirmed by considering the spontaneous emission process for the hydrogen atom interacting with the electromagnetic field. It is demonstrated that the t-4-decay and a faster decay are realized depending on the initial states, where the latter is estimated as t-8.
  • Physics of deformed special relativity: relativity principle revisited

    Girelli, Florian; Livine, Etera R.

    Resumo em Inglês:

    In many different ways, Deformed Special Relativity (DSR) has been argued to provide an effective limit of quantum gravity in almost-flat regime. Unfortunately, DSR is up to now plagued by many conceptual problems (in particular how it describes macroscopic objects) which forbids a definitive physical interpretation and clear predictions. Here we propose a consistent framework to interpret DSR. We extend the principle of relativity: the same way that Special Relativity showed us that the definition of a reference frame requires to specify its speed, we show that DSR implies that we must also take into account its mass. We further advocate a 5- dimensional point of view on DSR physics and the extension of the kinematical symmetry from the Poincar´e group to the Poincaré-de Sitter group (ISO(4; 1)). This leads us to introduce the concept of a pentamomentum and to take into account the renormalization of the DSR deformation parameter kappa. This allows the resolution of the "soccer ball problem" (definition of many-particle-states) and provides a physical interpretation of the non-commutativity and non-associativity of the addition the relativistic quadrimomentum.
  • Quantum physical relevance of the Einstein tensor

    Lamey, J.; Obermair, G. M.

    Resumo em Inglês:

    Taking quantum physics as well as large scale astronomical observations into account, a spacetime metric is introduced, such that the nonlinear part of the Einstein tensor contains effects of order $\hbar$.
  • Some remarks on the semi-classical limit of quantum gravity

    Livine, Etera R.

    Resumo em Inglês:

    One of the most important issues in quantum gravity is to identify its semi-classical regime. First the issue is to define for we mean by a semi-classical theory of quantum gravity, then we would like to use it to extract physical predictions. Writing an effective theory on a flat background is a way to address this problem and I explain how the non-commutative spacetime of deformed special relativity is the natural arena for such considerations. On the other hand, I discuss how the definition of the semi-classical regime can be formulated in a background independent fashion in terms of quantum information and renormalisation of geometry.
  • Lorentz invariance for mixed neutrinos

    Blasone, Massimo; Magueijo, João; Pacheco, Paulo Pires

    Resumo em Inglês:

    We show that a proper field theoretical treatment of mixed (Dirac) neutrinos leads to non-trivial dispersion relations for the flavor states. We analyze such a situation in the framework of the non-linear relativity schemes recently proposed by Magueijo and Smolin. We finally examine the experimental implications of our theoretical proposals by considering the spectrum and the end-point of beta decay in tritium.
  • Neutrino mixing as a source for cosmological constant

    Blasone, M.; Capolupo, A.; Capozziello, S.; Carloni, S.; Vitiello, G.

    Resumo em Inglês:

    We report on recent results showing that neutrino mixing may lead to a non-zero contribution to the cosmological constant. This contribution is of a completely different nature with respect to the usual one by a massive spinor field. We also study the problem of field mixing in Quantum Field Theory in curved space-time, for the case of a scalar field in the Friedmann-Robertson-Walker metric.
  • Spin flavor oscillation of neutrinos in rotating gravitational fields and their effects on pulsar kicks

    Lambiase, G.

    Resumo em Inglês:

    The origin of high velocities of pulsars is studied by considering the spin-flip conversion of neutrinos propagating in a gravitational field of a protoneutron star. For a rotating gravitational source (such as pulsars) with angular velocity , one finds that the spin connections (entering in the Dirac equation written in curved space time) induce an additional contribution to neutrino energy which is proportional to <FONT FACE=Symbol>w ×</FONT> p, with p the neutrino momentum. Such a coupling (spin-gravity coupling) can be responsible of pulsar kicks being the asymmetry of the neutrino emission generated by the relative orientation of the neutrino momentum p with respect to the angular velocity omega. As a consequence, the mechanism suggests that the motion of pulsars is correlated to their angular velocity omega. In this work we consider neutrinos propagating orthogonally to the magnetic field. The fractional asymmetry turns out to be independent on the magnetic field of the nascent protostar, and is only related to the angular velocity (deltap=p <FONT FACE=Symbol>» w</FONT>). As in the usual approaches, spin flip conversion is generated via the coupling of the neutrino magnetic momentum with the magnetic field. For our estimations, we use the large non-standard neutrino magnetic momentum provided by astrophysical and cosmological constraints, <FONT FACE=Symbol>m n</FONT> ~ 10-11 muB. - The connection with recent observations and statistical analysis is also discussed.
  • Generalized uncertainty principle, extra-dimensions and holography

    Scardigli, Fabio; Casadio, Roberto

    Resumo em Inglês:

    We consider Uncertainty Principles which take into account the role of gravity and the possible existence of extra spatial dimensions. Explicit expressions for such Generalized Uncertainty Principles in 4+n dimensions are given and their holographic properties investigated. In particular, we show that the predicted number of degrees of freedom enclosed in a given spatial volume matches the holographic counting only for one of the available generalizations and without extra dimensions.
  • Exact uncertainty principle and quantization: implications for the gravitational field

    Reginatto, M.

    Resumo em Inglês:

    The quantization of the gravitational field is discussed within the exact uncertainty approach. The method may be described as a Hamilton-Jacobi quantization of gravity. It differs from previous approaches that take the classical Hamilton-Jacobi equation as their starting point in that it incorporates some new elements, in particular the use of a formalism of ensembles in configuration space and the postulate of an exact uncertainty relation. These provide the fundamental elements needed for the transition from the classical theory to the quantum theory.
  • The Feynman propagator for quantum gravity: spin foams, proper time, orientation, causality and timeless-ordering

    Oriti, D.

    Resumo em Inglês:

    We discuss the notion of causality in Quantum Gravity in the context of sum-over-histories approaches, in the absence therefore of any background time parameter. In the spin foam formulation of Quantum Gravity, we identify the appropriate causal structure in the orientation of the spin foam 2-complex and the data that characterize it; we construct a generalised version of spin foam models introducing an extra variable with the interpretation of proper time and show that different ranges of integration for this proper time give two separate classes of spin foam models: one corresponds to the spin foam models currently studied, that are independent of the underlying orientation/causal structure and are therefore interpreted as a-causal transition amplitudes; the second corresponds to a general definition of causal or orientation dependent spin foam models, interpreted as causal transition amplitudes or as the Quantum Gravity analogue of the Feynman propagator of field theory, implying a notion of "timeless ordering".
  • Consistent histories and contrary inferences

    Nisticò, G.

    Resumo em Inglês:

    To perform a more transparent analysis of the problems raised by contrary inferences within Consistent History approach to Quantum Theory, we extend the formalism of the conceptual basis. According to our analysis, the conceptual difficulties arising from contrary inferences are ruled out.
  • Why is Schrödinger's equation linear?

    Parwani, Rajesh R.

    Resumo em Inglês:

    Information-theoretic arguments are used to obtain a link between the accurate linearity of Schr¨odinger's equation and Lorentz invariance: A possible violation of the latter at short distances would imply the appearance of nonlinear corrections to quantum theory. Nonlinear corrections can also appear in a Lorentz invariant theory in the form of higher derivative terms that are determined by a length scale, possibly the Planck length. It is suggested that the best place to look for evidence of such quantum nonlinear effects is in neutrino physics and cosmology.
  • 't Hooft's quantum determinism: path integral viewpoint

    Blasone, M.; Jizba, P.; Kleinert, H.

    Resumo em Inglês:

    We present a path integral formulation of 't Hooft's derivation of quantum from classical physics. Our approach is based on two concepts: Faddeev-Jackiw's treatment of constrained systems and Gozzi's path integral formulation of classical mechanics. This treatment is compared with our earlier one [quant-ph/0409021] based on Dirac-Bergmann's method.
  • Quantum probabilities versus event frequencies

    Anastopoulos, Charis

    Resumo em Inglês:

    Quantum probability is very different from classical probability. Part of this difference is manifested in the generic inability of stochastic processes to describe the results of multi-time measurements of quantum mechanical systems and the fact that the complex-valued temporal correlation functions of quantum theory have no interpretation in terms of multi-time measurements. By analysing experiments involving measurements at more than one moments of time, we conclude that this inequivalence must be manifested either as a failure of the quantum logic or as the inability to define probabilities in multi-time measurements because the relative frequencies do not converge. These alternatives can be empirically distinguished as they correspond to different behaviours of the statistical data in multi-time measurements.
  • Integers: irreducible guides in the search for a unified theory

    Korotkikh, Victor

    Resumo em Inglês:

    The notion of final theory results from a contrasting understanding of physical reality. Currently, different approaches aim to unify the four forces of nature and discuss whether a final theory may be possible. A key feature of a final theory is irreducibility, however this property has not been seriously exploited. In the paper we present an irreducible mathematical theory that describes physical systems in terms of formation processes of integer relations. The theory has integers and integer relations as the basic elements and is irreducible, because the formation processes are completely controlled by arithmetic. We suggest properties of the formation processes as irreducible guides in the search for a unified theory.
  • Generalized classical and quantum dynamics within a nonextensive approach

    Lavagno, A.

    Resumo em Inglês:

    On the basis of generalized classical kinetic equations, reproducing the stationary distribution of the Tsallis nonextensive thermostatistics, we formulate two generalized Schr¨odinger equations which satisfy the basic assumptions of the quantum mechanics under an appropriate generalization of the operator properties. Moreover, we study the generalization of the previously introduced dynamic equations in a relativistic regime and we apply our results to the study of the rapidity distribution in the relativistic heavy-ion collisions.
  • Quantum uncertainty in weakly non-ideal astrophysical plasma

    Gervino, G.; Lavagno, A.; Quarati, P.

    Resumo em Inglês:

    Galitskii and Yakimets showed that in dense or low temperature plasma, due to quantum uncertainty effect, the particle distribution function over momenta acquires a power-like tail even under conditions of thermodynamic equilibrium. We show that in weakly non-ideal plasmas, like the solar interior, both non-extensivity and quantum uncertainty should be taken into account to derive equilibrium ion distribution functions and to estimate nuclear reaction rates and solar neutrino fluxes. The order of magnitude of the deviation from the standard Maxwell-Boltzmann distribution can be derived microscopically by considering the presence of random electrical microfield in the stellar plasma. We show that such a nonextensive statistical effect can be very relevant in many nuclear astrophysical problems.
  • An efficient screening approach to be used in plasma modeling and ion-surface collision experiments

    Pomarico, J.; Iriarte, D. I.; Di Rocco, H. O.

    Resumo em Inglês:

    In this work we show that the Layzer theory for atomic calculations, not only provides a theoretical framework but also a powerful computational approach if correct rules for the calculation of the screening parameters are given. Using the virial as a model for potential energy and splitting of two-body operators as sum of one-body operators, a neat definition of screening is given, satisfying diverse physically indispensable properties. Many different experimental and theoretical results are reproduced with high accuracy, with no fitting procedure involving energy levels or numerical potentials. A C++ code and an executable file are available upon request.
  • A general creation-annihilation model with absorbing states

    Dantas, Wellington G.; Ticona, Armando; Stilck, Jürgen F.

    Resumo em Inglês:

    A one dimensional non-equilibrium stochastic model is proposed where each site of the lattice is occupied by a particle, which may be of type A or B. The time evolution of the model occurs through three processes: autocatalytic generation of A and B particles and spontaneous conversion A -> B. The two-parameter phase diagram of the model is obtained in one- and two-site mean field approximations, as well as through numerical simulations and exact solution of finite systems extrapolated to the thermodynamic limit. A continuous line of transitions between an active and an absorbing phase is found. This critical line starts at a point where the model is equivalent to the contact process and ends at a point which corresponds to the voter model, where two absorbing states coexist. Thus, the critical line ends at a point where the transition is discontinuous. Estimates of critical exponents are obtained through the simulations and finite-size-scaling extrapolations, and the crossover between universality classes as the voter model transition is approached is studied.
  • Collisional transport in axisymmetric plasma columns with strong longitudinal flows: application to solar loops

    Tsypin, V. S.; Galvão, R.M.O.

    Resumo em Inglês:

    In this work we analyze the transport processes in solar loops considering a collisional plasma and high longitudinal plasma flow. The general theory of the neoclassical transport in toroidal configurations with a noncircular cross-section is applied to explain the transport processes in some kinds of solar loops, modeling the solar loop as a toroidal plasma column. The plasma is assumed to be in the collisional regime and to have particle longitudinal flow along the solar loop axis. The poloidal velocity and the radial fluxes of the particles and the ion heat flux are derived in this article. It is shown that the particle poloidal velocity can be measured giving rise to the possibility of having additional connections between the plasma macroscopic parameters, which are very important for the solar loops diagnostic. It is also shown that the particle and heat fluxes are on the ''classical'' level, within the factor of an order of magnitude. We hope that such an approach (together with other theories) can help to explain the transport processes in solar loops, whose shapes are similar to toroidal configurations.
  • Spectral derivation of the ornstein-zernike decay for four-point functions

    Auil, F.; Barata, J. C. A.

    Resumo em Inglês:

    In this note we discuss the relation between the Ornstein-Zernike decay of certain four-point functions (''energy-energy correlations'') in lattice spin systems and spectral properties of the transfer matrix, related to the property of two-particle asymptotic completeness in (massive) Euclidean lattice quantum field theories.
  • Regularizations: different prescriptions for identical situations

    Gambin, E.; Lobo, C. O.; Dallabona, G.; Battistel, O. A.

    Resumo em Inglês:

    We present a discussion where the choice of the regularization procedure and the routing for the internal lines momenta are put at the same level of arbitrariness in the analysis of Ward identities involving simple and well-known problems in quantum field theory. They are the complex self-interacting scalar field and two simple models where the scalar-vector-vector and axial-vector-vector process are pertinent. We show that, in all these problems, the conditions to symmetry relations preservation are put in terms of the same combination of divergent Feynman integrals, which are evaluated in the context of a very general calculational strategy, concerning the manipulations and calculations involving divergences. Within the adopted strategy, all the arbitrariness intrinsic to the problem are still maintained in the final results and, consequently, a perfect map can be obtained with the corresponding results of traditional regularization techniques. We show that, when we require an universal interpretation for the arbitrariness involved, in order to get consistency with all stated physical constraints, a strong condition is imposed for regularizations which automatically eliminates the ambiguities associated to the routing of the internal lines momenta of loops. The conclusion is clean and sound: the association between ambiguities and unavoidable symmetry violations in Ward identities cannot be maintained if an unique prescription is required for identical situations in the evaluation of divergent physical amplitudes.
  • Sculpturing squeezed states to get highly excited fock states

    Monteiro, Paula B.; Baseia, B.; Avelar, A. T.; Malbouisson, J. M. C.

    Resumo em Inglês:

    We study two experimental schemes generating highly excited number states starting from an initial squeezed state. One of the schemes works for stationary fields, the other for traveling ones.
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