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Semiclassical evolution of correlations between observables
Get PDFThe trace of an arbitrary product of quantum operators with the density operator is rendered as a multiple phase space integral of the product of their Weyl symbolswith the Wigner function. Interspersing the factors with various evolution operators, one obtains an evolving correlation. The kernel for the matching multiple integral thatevolves within the Weyl representation is identified with the trace of a single compound unitary operator. Its evaluation within a semiclassical approximation then becomes asum over the periodic trajectories of the corresponding classical compound canonical transformation. The search for periodic trajectories can be bypassed by an exactly equivalent initialvalue scheme, which involves a change of integration variable and a reduced compound unitary operator. Restriction of all the operators to observables with smooth nonoscillatoryWeyl symbols reduces the evolving correlation to a single phase space integral. If each observable undergoes independent Heisenberg evolution, the overallcorrelation evolves classically. Otherwise, the kernel acquires a nonclassical phase factor, though it still depends on a purely classical compound trajectory: e.g. the fasefor a double return of the quantum Loschmidt echo does not coincide with twice the phase for a single echo. 
A large deviation analysis on the near-equivalence between external and internal reservoirs
Get PDFWithin the spirit of van Kampen's \Langevin approach", we discuss the limits of validity of rephrasing the non-equilibrium problem of a particle subject to an external (work)reservoir | a system where the uctuation-dissipation is not veried | into the simpler case with an internal (heat) reservoir for which the uctuations and the dissipation arisefrom the same source. Using a convenient mapping of the thermomechanical parameters we show that, counter-intuitively, such approach is not only valid for steady state time independent quantities, but also for time dependent thermostatistical quantities, namelythe injected and dissipated uxes. We connect this result with the problem of large devi- ations and conclude that, in this context, we can only distinguish reservoirs by analysingthe \uctuations of accumulated uctuations". As a by-product, we learn that the best reference approximation to the large deviation functions of a non-Markovian external reservoir system is not the respective internal reservoir limit | as often assumed and sug-gested by the Langevin approach | but its internal reservoir analogue system obtained from the mapping of the original thermomechanical parameters
Beyond gauge theory: Hilbert space positivity and causal localization in the presence of vector mesons
Get PDFThe Hilbert space formulation of interacting s = 1 vector-potentials stands in an interesting con-trast with the point-local Krein space setting.of gauge theory. Already in the absence of interactionsthe Wilson loop in a Hilbert space setting has a ”topological property” which is missing in the gaugetheoretic description (Haag duality, Aharonov-Bohm effect); the conceptual differences increase in thepresence of interactions.The Hilbert space positivity weakens the causal localization properties if interacting fields whichresults in the replacement of the gauge-variant point-local matter fields in Krein space by string-localphysical fields in Hilbert space. The gauge invariance of the perturbative S-matrix corresponds to itsindependence of the spacelike string direction of its interpolating.fields. In contrast to gauge theory,whose physical range is limited to gauge invariant perturbative S-matrix and local observables, itsHilbert space string-local counterpart in is a full-fledged quantum field theory (QFT).The new setting reveals that the Lie-structure of self-coupled vector mesons results from pertur-bative implementation of the causal localization principles of QFT
Invariant PDEs of Conformal Galilei Algebra as deformations: cryptohermiticity and contractions
Get PDFAbstract: In two papers, JPA: Math. Theor. 46, 405204 (2013) and JMP 56, 031701 (2015), second-order invariant PDEs of the centrally extended Conformal Galilei Algebras, were constructed (for continuous and, respectively, discrete spectrum). We investigate here the general class of second-order invariant PDEs, pointing out that they are deformations of decoupled systems. For the uniquedeformation parameter belongs to the fundamental domain . The invariant PDE with discrete spectrum induces a cryptohermitian operator possessing the same spectrum as two decoupled oscillators of given energy . The normalization implies, for , the admissible critical values (the negative energy solutions correspond to a special case of Pais-Uhlenbeck oscillator). \parUnitarily inequivalent operators, acting on the Hilbert space, are obtained for the deformation parameter belonging to the fundamental domain. The undeformed case corresponds to a decoupled cryptohermitian operator with enhanced symmetry at the critical values . Two inequivalent -generator symmetry algebras are found at and , respectively. The Conformal Galilei Algebra is not a subalgebra of the decoupled symmetry algebra. Its contraction corresponds to a -generator subalgebra of the decoupled symmetry algebra.\parThe features of the invariant PDEs are briefly discussed. 
Interface para Detectores de Radiação Timepix baseada em plataforma FPGA.
Get PDF Medipix é uma família de detectores de área para radiação, formados por uma matriz de pixels híbridos, desenvolvida por um consórcio colaborativo no CERN, tendo como foco inicial aplicações medicinais. Atual-mente, existem as seguintes versões de detectores: Medipix, Medipix-2, Timepix, Medipix-3, Medipix-3RX e Timepix3. Apresentamos o desenvolvimento de uma interface para aquisição de dados para até nove chips da versão Timepix. Esta interface servirá de base para um Telescópio de Múons, e poderá ser utilizada em projetos relacionados ao detector VELO, no experimento LHCb. Foi desenvolvido um conjunto de módulos eletrônicos e programas para a plataforma NI-PXI via FPGA. Apresentamos resultados de testes realizados pelo proce-dimento de desabilitação de pixels do Timepix por uma máscara digital, para demonstrar a funcionalidade da interface desenvolvida
Neutrinos Massivos
Get PDFO objetivo deste trabalho é introduzir as principais idéias por trás da física de neutrinos. A proposta é apresentar os fundamentos sobre os quais são construídos todos os modelos e teorias além do Modelo Padrão no setor de neutrinos. Além de uma mínima familiaridade com a equação de Dirac e um primeiro contato com o modelo de Salam-Glashow-Weinberg, nenhum outro conhecimento em física de partículas e TQC é pressuposto do leitor. Com isso visamos ser a porta de entrada para a pesquisa na física de neutrinos. Para isso começaremos com uma revisão do modelo de Salam-Glashow-Weinberg da unificação eletrofraca. Estudaremos então as principais consequências fenomenológicas deste modelo e até onde elas concordam com experimentos, como destaque para a violação de CP. Aprenderemos que uma extensão ao Modelo Padrão, devido às massas não nulas dos neutrinos, é necessária e discutiremos as possibilidades teóricas atualmente permitidas pelas observações. Concentraremos maior atenção em uma possibilidade específica, a de neutrinos serem férmions de Majorana, para construir o popular Mecanismo Seesaw, cuja função será suprimir as massas dos neutrinos em relação aos demais férmions do Modelo Padrão. Encerraremos então deduzindo as principais fórmulas da física de oscilação de neutrinos, pois é este o fenômeno observado experimentalmente, bem como os mais recentes resultados para os ângulos de mistura
Current algebra for a generalized two-site Bose-Hubbard model
Get PDFWe present a current algebra for a generalized two-site Bose-Hubbard model and use it to getthe quantum dynamics of the currents. For different choices of the Hamiltonian parameters we getdifferent currents dynamics. We generalize the Heisenberg equation of motion to write the n-th timederivative of any operator
Desenvolvimento de um sistema SCADA para operação de um Laser de Elétrons Livres
Get PDFEste trabalho apresenta o desenvolvimento de um sistema de Controle Supervisório e de Aquisição de Dados ({\it Supervisory Control and Data Acquisition -- SCADA}) para a operação de um Laser de Elétrons Livres ({\it Free Electron Laser - FEL}) [1] baseado em uma rede Intranet e na linguagem gráfica LabVIEW. O FEL é uma fonte de radiação eletromagnética monocromática, coerente, intensa e sintonizável produzida através da interação de um feixe de elétrons relativísticos com um campo magnético estático ondulado [2]. A operação de um FEL envolve o controle e teste de diversos transdutores (sensores e atuadores) responsáveis pelo transporte, monitoramento e centralização do feixe de elétrons e da qualidade da radiação laser. Os sistemas SCADA se apresentam especialmente adaptados para processos, de média a grande complexidade, que demandam supervisão, escalabilidade, modularidade, monitoramento, automação de processos remotos e conectividade a bancos de dados. O trabalho aqui apresentado visa contribuir para elaboração de uma proposta para construção de um FEL no país, o {\it Brazilian Free Electron Laser - BraFEL} [3]. 
-oscillators from second-order invariant PDEs of the centrally extended Conformal Galilei Algebras
No full textWe construct, for any given , the second-order, linear PDEs which are invariant under the centrally extended Conformal Galilei Algebra. \par At the given , two invariant equations in one time and space coordinates are obtained.The first equation possesses a continuum spectrum and generalizes the free Schr\"odinger equation (recovered for ) in dimension. The second equation (the ``-oscillator") possesses a discrete, positive spectrum. It generalizes the -dimensional harmonic oscillator (recovered for ). The spectrum of the -oscillator, derived from a specific h.w.r., is explicitly presented.\parThe two sets of invariant PDEs are determined by imposing (representation-dependent) {\it on-shell invariant conditions} both for {\it degree} operators (those with continuum spectrum) and for {\it degree } operators(those with discrete spectrum).The on-shell condition is better understood by enlarging the Conformal Galilei Algebras with the addition of certain second-order differential operators. Two compatible structures (the algebra/superalgebra duality) are defined for the enlarged set of operators. 
Thermostatistics of small non-linear systems: Poissonian athermal bath
Get PDFWe extend the study presented in [Phys. Rev. E 90, 022110 (2014)] to the case of a smallsystem subject to non-linear interaction and in contact with an athermal shot-noise reservoir.We rst focus on steady state properties, namely on the impact of the singular measure of thereservoir in the steady state energy. Then, we introduce the concept of temperatures of higher-order, which aim to represent the effect produced by the cumulants of the noise of order largerthan 2, and new response functions such as high-order specic heats, that zero out when thesystem is thermal or linear. Afterwards, we study the effect of the nature of the noise in theheat and energy uxes and determine asymptotic expressions for its large deviation functions.Finally, in analysing the probabilistics of the injected power, jinj, we verify that the exponentialform of its uctuation relation is only asymptotically valid whereas in the thermal case is validfor all jinj