Momentum flux density, kinetic energy density and their fluctuations for one-dimensional confined gases of non-interacting fermions

We present a Green's function method for the evaluation of the particle density profile and of the higher moments of the one-body density matrix in a mesoscopic system of N Fermi particles moving independently in a linear potential. The usefulness of the method is illustrated by applications to a Fermi gas confined in a harmonic potential well, for which we evaluate the momentum flux and kinetic energy densities as well as their quantal mean-square fluctuations. We also study some properties of the kinetic energy functional E_{kin}[n(x)] in the same system. Whereas a local approximation to the kinetic energy density yields a multi-valued function, an exact single-valued relationship between the density derivative of E_{kin}[n(x)] and the particle density n(x) is demonstrated and evaluated for various values of the number of particles in the system.Comment: 10 pages, 5 figure

Kinetics of defect formation in chemically vapor deposited (CVD) graphene during laser irradiation: The case of Raman investigation

The effect of laser irradiation on chemically vapor deposited (CVD) graphene was studied by analyzing the temporal evolution of Raman spectra acquired under various illumination conditions. The spectra showed that the normalized intensity of the defect-related peak increases with the square root of the exposure time and varies almost linearly with the laser power density. Furthermore, the hardness of graphene to radiation damage depends on its intrinsic structural quality. The results suggest that, contrary to the common belief, micro-Raman spectroscopy cannot be considered a noninvasive tool for the characterization of graphene. The experimental observations are compatible with a model that we derived from the interpretative approach of the Staebler–Wronski effect in hydrogenated amorphous silicon; this approach assumes that the recombination of photoexcited carriers induces the breaking of weak C–C bonds

A torsional completion of gravity for Dirac matter fields and its applications to neutrino oscillations

In this paper, we consider the torsional completion of gravitation for an underlying background filled with Dirac fields, applying it to the problem of neutrino oscillations: we discuss the effects of the induced torsional interactions as corrections to the neutrino oscillation mechanism.Comment: 4 page

Influência de diferentes substratos no crescimento e desenvolvimento de mudas de morangueiro.

bitstream/item/79603/1/Comunicado-285.pd

Desenvolvimento inicial de pitangueira a partir de sementes de frutos em diferentes estágios de maturação.

bitstream/item/61611/1/Comunicado-278.pd

Effect of grain refinement on enhancing critical current density and upper critical field in undoped MgB2 ex-situ tapes

Ex-situ Powder-In-Tube MgB2 tapes prepared with ball-milled, undoped powders showed a strong enhancement of the irreversibility field H*, the upper critical field Hc2 and the critical current density Jc(H) together with the suppression of the anisotropy of all of these quantities. Jc reached 104 A/cm2 at 4.2 K and 10 T, with an irreversibility field of about 14 T at 4.2 K, and Hc2 of 9 T at 25 K, high values for not-doped MgB2. The enhanced Jc and H* values are associated with significant grain refinement produced by milling of the MgB2 powder, which enhances grain boundary pinning, although at the same time also reducing the connectivity from about 12% to 8%. Although enhanced pinning and diminished connectivity are in opposition, the overall influence of ball milling on Jc is positive because the increased density of grains with a size comparable with the mean free path produces strong electron scattering that substantially increases Hc2, especially Hc2 perpendicular to the Mg and B planes.Comment: 26 pages, 9 figures, submitted to J. Appl. Phy