Nonextensive Quantum H-Theorem

A proof of the quantum $H$-theorem taking into account nonextensive effects on the quantum entropy $S^Q_q$ is shown. The positiveness of the time variation of $S^Q_q$ combined with a duality transformation implies that the nonextensive parameter $q$ lies in the interval [0,2]. It is also shown that the equilibrium states are described by quantum $q$-power law extensions of the Fermi-Dirac and Bose-Einstein distributions. Such results reduce to the standard ones in the extensive limit, thereby showing that the nonextensive entropic framework can be harmonized with the quantum distributions contained in the quantum statistics theory.Comment: 5 pages, LaTe

Adiabatic pumping through a quantum dot in the Kondo regime: Exact results at the Toulouse limit

Transport properties of ultrasmall quantum dots with a single unpaired electron are commonly modeled by the nonequilibrium Kondo model, describing the exchange interaction of a spin-1/2 local moment with two leads of noninteracting electrons. Remarkably, the model possesses an exact solution when tuned to a special manifold in its parameter space known as the Toulouse limit. We use the Toulouse limit to exactly calculate the adiabatically pumped spin current in the Kondo regime. In the absence of both potential scattering and a voltage bias, the instantaneous charge current is strictly zero for a generic Kondo model. However, a nonzero spin current can be pumped through the system in the presence of a finite magnetic field, provided the spin couples asymmetrically to the two leads. Tunneling through a Kondo impurity thus offers a natural mechanism for generating a pure spin current. We show, in particular, that one can devise pumping cycles along which the average spin pumped per cycle is closely equal to $\hbar$. By analogy with Brouwer's formula for noninteracting systems with two driven parameters, the pumped spin current is expressed as a geometrical property of a scattering matrix. However, the relevant %Alex: I replaced topological with geometrical in the sentence above scattering matrix that enters the formulation pertains to the Majorana fermions that appear at the Toulouse limit rather than the physical electrons that carry the current. These results are obtained by combining the nonequilibrium Keldysh Green function technique with a systematic gradient expansion, explicitly exposing the small parameter controlling the adiabatic limit.Comment: 14 pages, 3 figures, revised versio

The M2/M5 BPS Partition Functions from Supergravity

In the framework of the AdS/CFT duality, we calculate the supersymmetric partition function of the superconformal field theories living in the world volume of either $N$ $M2$-branes or $N$ $M5$-branes. We used the dual supergravity partition function in a saddle point approximation over supersymmetric Black Holes. Since our BHs are written in asymptotically global $AdS_{d+1}$ co-ordinates, the dual SCFTs are in $R x S^{d}$ for $d=2,5$. The resulting partition function shows phase transitions, constraints on the phase space and allowed us to identify unstable BPS Black hole in the $AdS$ phase. These configurations should correspond to unstable configurations in the dual theory. We also report an intriguing relation between the most general Witten Index, computed in the above theories, and our BPS partition functions.Comment: 9 pages, 2 columns, 4 figures, revtex, typos corrected, reference adde

Ponto de murcha permanente do feijoeiro comum em Latossolo Vermelho-Amarelo distrófico em Rondônia.

Objetivou-se neste trabalho determinar o ponto de murcha permanente (PMP) e a evapotranspiração em função da umidade do solo, para o feijoeiro comum (Phaseolus vulgaris L.), em estádio fenológico de pré-florescimento em Latossolo Vermelho- Amarelo distrófico representativo no município de Porto Velho-RO.Organizado por: Henrique Nery Cipriani; Alaerto Luiz Marcolan; Fernando Machado Pfeifer: Alexandre Martins Abdão dos Passos; Marcelo Curitiba Espíndula; Angelo Mansur Mendes

Interplay between disorder, quantum and thermal fluctuations in ferromagnetic alloys: The case of UCu2Si(2-x)Ge(x)

We consider, theoretically and experimentally, the effects of structural disorder, quantum and thermal fluctuations in the magnetic and transport properties of certain ferromagnetic alloys.We study the particular case of UCu2Si(2-x)Ge(x). The low temperature resistivity, rho(T,x), exhibits Fermi liquid (FL) behavior as a function of temperature T for all values of x, which can be interpreted as a result of the magnetic scattering of the conduction electrons from the localized U spins. The residual resistivity, rho(0,x), follows the behavior of a disordered binary alloy. The observed non-monotonic dependence of the Curie temperature, Tc(x), with x can be explained within a model of localized spins interacting with an electronic bath whose transport properties cross-over from ballistic to diffusive regimes. Our results clearly show that the Curie temperature of certain alloys can be enhanced due to the interplay between quantum and thermal fluctuations with disorder.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let

Centrifugal force induced by relativistically rotating spheroids and cylinders

Starting from the gravitational potential of a Newtonian spheroidal shell we discuss electrically charged rotating prolate spheroidal shells in the Maxwell theory. In particular we consider two confocal charged shells which rotate oppositely in such a way that there is no magnetic field outside the outer shell. In the Einstein theory we solve the Ernst equations in the region where the long prolate spheroids are almost cylindrical; in equatorial regions the exact Lewis "rotating cylindrical" solution is so derived by a limiting procedure from a spatially bound system. In the second part we analyze two cylindrical shells rotating in opposite directions in such a way that the static Levi-Civita metric is produced outside and no angular momentum flux escapes to infinity. The rotation of the local inertial frames in flat space inside the inner cylinder is thus exhibited without any approximation or interpretational difficulties within this model. A test particle within the inner cylinder kept at rest with respect to axes that do not rotate as seen from infinity experiences a centrifugal force. Although the spacetime there is Minkowskian out to the inner cylinder nevertheless that space has been induced to rotate, so relative to the local inertial frame the particle is traversing a circular orbit.Comment: 12 pages, 2 figure

Electronic excitation of carbonyl sulphide (COS) by high-resolution vacuum ultraviolet photoabsorption and electron-impact spectroscopy in the energy region from 4 to 11 eV

The electronic state spectroscopy of carbonyl sulphide, COS, has been investigated using high resolution vacuum ultraviolet photoabsorption spectroscopy and electron energy loss spectroscopy in the energy range of 4.0–10.8 eV. The spectrum reveals several new features not previously reported in the literature. Vibronic structure has been observed, notably in the low energy absorption dipole forbidden band assigned to the (4π←3π) (1Δ←1Σ+) transition, with a new weak transition assigned to (1Σ−←1Σ+) reported here for the first time. The absolute optical oscillator strengths are determined for ground state to 1Σ+ and 1Π transitions. Based on our recent measurements of differential cross sections for the optically allowed (1Σ+ and 1Π) transitions of COS by electron impact, the optical oscillator strength f0 value and integral cross sections (ICSs) are derived by applying a generalized oscillator strength analysis. Subsequently, ICSs predicted by the scaling are confirmed down to 60 eV in the intermediate energy region. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of carbonyl sulphide in the upper stratosphere (20–50 km)