Time dependent transformations in deformation quantization

We study the action of time dependent canonical and coordinate transformations in phase space quantum mechanics. We extend the covariant formulation of the theory by providing a formalism that is fully invariant under both standard and time dependent coordinate transformations. This result considerably enlarges the set of possible phase space representations of quantum mechanics and makes it possible to construct a causal representation for the distributional sector of Wigner quantum mechanics.Comment: 16 pages, to appear in the J. Math. Phy

Fruit fly management research, transcriptome analysis and first evidence of RNAi in Anastrepha fraterculus (Diptera: Tephritidae).

Tese (Doutorado) - Programa de Pós-Graduação em Fitossanidade. Universidade Federal de Pelotas, Pelotas. Orientador: Dori Edson Nava, Co-orientador: Moisés João Zotti, Guy Smagghe

Limiting fragmentation in heavy-ion collisions and percolation of strings

The observed limiting fragmentation of charged particle distributions in heavy ion collisions is difficult to explain as it does not apply to the proton spectrum itself. On the other hand, string percolation provides a mechanism to regenerate fast particles, eventually compensating the rapidity shift (energy loss) of the nucleons. However a delicate energy-momentum compensation is required, and in our framework we see no reason for limiting fragmentation to be exact. A prediction, based on percolation arguments, is given for the charged particle density in the full rapidity interval at LHC energy $(\sqrt s =5500 GeV)$.Comment: 9 pages, 2 figures (2 eps files), late

Half Quantization

A general dynamical system composed by two coupled sectors is considered. The initial time configuration of one of these sectors is described by a set of classical data while the other is described by standard quantum data. These dynamical systems will be named half quantum. The aim of this paper is to derive the dynamical evolution of a general half quantum system from its full quantum formulation. The standard approach would be to use quantum mechanics to make predictions for the time evolution of the half quantum initial data. The main problem is how can quantum mechanics be applied to a dynamical system whose initial time configuration is not described by a set of fully quantum data. A solution to this problem is presented and used, as a guideline to obtain a general formulation of coupled classical-quantum dynamics. Finally, a quantization prescription mapping a given classical theory to the correspondent half quantum one is presented.Comment: 20 pages, LaTex file, Substantially revised versio

Earnings management and debt in private companies: The effect of economic adjustment programmes

Our study analyses the relationship between the level of earnings management and the debt of unlisted companies in two countries liable to economic adjustment programmes – Portugal and Ireland – between 2008 and 2016. We also analyse whether there are differences between both countries in what results are concerned. In a sample of 970 unlisted companies, and according the discretionary accruals, we find evidence of a positive relationship between the level of debt and the level of earnings management, thus concluding that the level of this relationship is different in each country. We also demonstrate that during the period of time in which the financial support occurred, there was mitigation in the relationship between the level of earnings management and indebtedness.info:eu-repo/semantics/acceptedVersio

The Left-Right SU(3)(L)xSU(3)(R)xU(1)(X) Model with Light, keV and Heavy Neutrinos

We construct a full left-right model for the electroweak interactions based on the $SU(3)_{L}\otimes SU(3)_{R}\otimes U(1)_{X}$ gauge symmetry. The fermion content of the model is such that anomaly cancellation restricts the number of families to be a multiple of three. One of the most important features of the model is the joint presence of three light active neutrinos, three additional neutrinos at keV mass scale, and six heavy ones with masses around\textbf{$10^{11}$} GeV. They form a well-motivated part of the spectrum in the sense they address challenging problems related to neutrino oscillation, warm dark matter, and baryogenesis through leptogenesis.Comment: 11 pages. Small corrections and typos fixed. Accepted for publication in PR

Coherent States Expectation Values as Semiclassical Trajectories

We study the time evolution of the expectation value of the anharmonic oscillator coordinate in a coherent state as a toy model for understanding the semiclassical solutions in quantum field theory. By using the deformation quantization techniques, we show that the coherent state expectation value can be expanded in powers of $\hbar$ such that the zeroth-order term is a classical solution while the first-order correction is given as a phase-space Laplacian acting on the classical solution. This is then compared to the effective action solution for the one-dimensional \f^4 perturbative quantum field theory. We find an agreement up to the order \l\hbar, where \l is the coupling constant, while at the order \l^2 \hbar there is a disagreement. Hence the coherent state expectation values define an alternative semiclassical dynamics to that of the effective action. The coherent state semiclassical trajectories are exactly computable and they can coincide with the effective action trajectories in the case of two-dimensional integrable field theories.Comment: 20 pages, no figure