Navegando por Autor "Sampaio, Marcos Donizeti Rodrigues"
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Item Entanglement of self interacting scalar fields in an expanding spacetime.(2016) Costa, Helder Alexander Santos; Souza, Gustavo Henrique Costa de; Mansfield, Paul; Paz, Irismar Gonçalves da; Sampaio, Marcos Donizeti RodriguesWe evaluate self-interaction effects on the quantum correlations of field modes of opposite mo- menta for scalar λφ4 theory in a two-dimensional asymptotically flat Robertson-Walker spacetime. Such correlations are encoded both in the von-Neumann entropy defined through the reduced den- sity matrix in one of the modes and in the covariance expressed in terms of the expectation value of the number operators for each mode in the evolved state. The entanglement between field modes carries information about the underlying spacetime evolution.Item Exotic looped trajectories via quantum marking.(2017) Oliveira Júnior, José Geraldo Gonçalves de; Souza, Gustavo Henrique Costa de; Cabral, Luís Antonio; Paz, Irismar Gonçalves da; Sampaio, Marcos Donizeti RodriguesWe provide an analytical theoretical study of exotic looped trajectories (ELTs) in a double-slit interferometer with quantum marking. We propose using an excited Rydberg-like atom and superconducting cavities as which-way detectors, just as in the Scully–Englert–Walther interferometer. We show that the resonant interaction between the atom and the field in the cavities can be used to eliminate the effect of non-exotic trajectories and exhibit only the effect of ELTs in the interference pattern. We quantitatively describe our results for Rubidium atoms and suggest this framework as a scheme to measure exotic looped paths and deviations from the standard superposition principle.Item Fringe visibility of exotic trajectories for matter waves in a double-slit experiment.(2019) Vieira, Carlos Henrique da Silva; Costa, Helder Alexander Santos; Souza, Gustavo Henrique Costa de; Sampaio, Marcos Donizeti Rodrigues; Paz, Irismar Gonçalves daWe theoretically study the fringe visibility of exotic looped trajectories in double-slit experiments with matter waves. We consider the relative intensity at x=0x=0 as a function of the time-of-flight from the double-slit to the screen inside the interferometer. This allows us to define a fringe visibility associated with the contribution to the interference pattern given by exotic looped trajectories. We demonstrate that the Sorkin parameter is given in terms of this visibility and of the axial phases which include the Gouy phase. Thus, the effect of exotic looped trajectories can be attested by measuring deviations from unity for the fringe visibility. We show that the effect of exotic trajectories can be increased by adjusting the parameters of the double-slit apparatus in the Fresnel regime.Item Implicit regularization beyond one-loop order : scalar field theories.(2007) Pontes, Carlos Renato; Scarpelli, Antônio Paulo Baêta; Sampaio, Marcos Donizeti Rodrigues; Nemes, Maria CarolinaImplicit regularization (IR) has been shown as a useful momentum space tool for perturbative calculations in dimension-specific theories, such as chiral gauge, topological and supersymmetric quantum field theoretical models at one-loop level. In this paper, we aim at generalizing systematically IR to be applicable beyond one-loop order. We use a scalar field theory as an example and pave the way for the extension to quantum field theories which are richer from the symmetry content viewpoint. Particularly, we show that a natural (minimal) renormalization scheme emerges, in which the infinities displayed in terms of integrals in one internal momentum are subtracted, whereas infrared and ultraviolet modes do not mix and therefore leave no room for ambiguities. A systematic cancellation of the infrared divergences at any loop order takes place between the ultraviolet finite and divergent parts of the amplitude for non-exceptional momenta leaving, as a by-product, a renormalization group scale.Item On the equivalence between implicit regularization and constrained differential renormalization.(2008) Pontes, Carlos Renato; Scarpelli, Antônio Paulo Baêta; Sampaio, Marcos Donizeti Rodrigues; Fernandes, José Luiz Acebal; Nemes, Maria CarolinaConstrained differential renormalization (CDR) and the constrained version of implicit regularization are two regularization independent techniques that do not rely on dimensional continuation of the space-time. These two methods, which have rather distinct bases, have been successfully applied to several calculations, which show that they can be trusted as practical, symmetry invariant frameworks (gauge and supersymmetry included) in perturbative computations even beyond one-loop order. In this paper, we show the equivalence between these two methods at one-loop order. We show that the configuration space rules of CDR can be mapped into the momentum-space procedures of implicit regularization, the major principle behind this equivalence being the extension of the properties of regular distributions to regularized ones.Item Quantum estimation in neutrino oscillations.(2017) Nogueira, Edson Cezar Moraes; Souza, Gustavo Henrique Costa de; Varizi, Adalberto Deybe; Sampaio, Marcos Donizeti RodriguesIn this work, we analyze two-°avor neutrino oscillations within the framework of quantum estimation theory (QET). We compute the quantumFischer information (QFI) for the mixing angle and show that mass measurements are the ones that achieve optimal precision. We also study the Fischer information (FI) associated with °avor measurements and show that they are optimized at speci¯c neutrino times-of-°ight. Therefore, although the usual population measurement does not realize the precision limit set by the QFI, it can in principle be implemented with the best possible sensitivity to . We investigate how these quanti¯ers relate to the single-particle, mode entanglement in neutrino oscillations. We demonstrate that this form of entanglement does not enhance either of them. In particular, our results show that in single-particle settings, entanglement is not directly connected with the enhancement of precision in metrological tasks.