Extension of explicit formulas in Poissonian white noise analysis using harmonic analysis on configuration spaces

Harmonic analysis on configuration spaces is used in order to extend explicit expressions for the images of creation, annihilation, and second quantization operators in L2-spaces with respect to Poisson point processes to a set of functions larger than the space obtained by directly using chaos expansion. This permits, in particular, to derive an explicit expression for the generator of the second quantization of a sub-Markovian contraction semigroup on a set of functions which forms a core of the generator.

Anomalous spin-related quantum phase in mesoscopic hole rings

We have obtained numerically exact results for the spin-related geometric quantum phases that arise in p-type semiconductor ring structures. The interplay between gate-controllable (Rashba) spin splitting and quantum-confinement-induced mixing between hole-spin states causes a much higher sensitivity of magnetoconductance oscillations to external parameters than previously expected. Our results imply a much-enhanced functionality of hole-ring spin-interference devices and shed new light on recent experimental findings.

Sagnac rotational phase shifts in a mesoscopic electron interferometer with spin-orbit interactions

The Sagnac effect is an important phase coherent effect in optical and atom interferometers where rotations of the interferometer with respect to an inertial reference frame result in a shift in the interference pattern proportional to the rotation rate. Here, we analyze the Sagnac effect in a mesoscopic semiconductor electron interferometer. We include in our analysis the Rashba spin-orbit interactions in the ring. Our results indicate that spin-orbit interactions increase the rotation-induced phase shift. We discuss the potential experimental observability of the Sagnac phase shift in such mesoscopic systems.

Effects of a quantum measurement on the electric conductivity : Application to graphene

We generalize the standard linear-response (Kubo) theory to obtain the conductivity of a system that is subject to a quantum measurement of the current. Our approach can be used to specifically elucidate how back-action inherent to quantum measurements affects electronic transport. To illustrate the utility of our general formalism, we calculate the frequency-dependent conductivity of graphene and discuss the effect of measurement-induced decoherence on its value in the dc limit. We are able to resolve an ambiguity related to the parametric dependence of the minimal conductivity.

Aplicações da q-Álgebra em física da matéria condensada

We address the generalization of thermodynamic quantity q-deformed by q-algebra that describes a general algebra for bosons and fermions . The motivation for our study stems from an interest to strengthen our initial ideas, and a possible experimental application. On our journey, we met a generalization of the recently proposed formalism of the q-calculus, which is the application of a generalized sequence described by two parameters deformation positive real independent and q1 and q2, known for Fibonacci oscillators . We apply the wellknown problem of Landau diamagnetism immersed in a space D-dimensional, which still generates good discussions by its nature, and dependence with the number of dimensions D, enables us future extend its application to systems extra-dimensional, such as Modern Cosmology, Particle Physics and String Theory. We compare our results with some experimentally obtained performing major equity. We also use the formalism of the oscillators to Einstein and Debye solid, strengthening the interpretation of the q-deformation acting as a factor of disturbance or impurity in a given system, modifying the properties of the same. Our results show that the insertion of two parameters of disorder, allowed a wider range of adjustment , i.e., enabling change only the desired property, e.g., the thermal conductivity of a same element without the waste essence

Minimum size for the occurrence of vortex matter in a square mesoscopic superconductor

The study of superconducting samples in mesoscopic scale presented a remarkable improvement during the last years. Certainly, such interest is based on the fact that when the size of the samples is close to the order of the temperature dependent coherence length xi(T), and/or the size of the penetration depth lambda(T), there are some significant modifications on the physical properties of the superconducting state. This contribution tests the square cross-section size limit for the occurrence (or not) of vortices in mesoscopic samples of area L-2, where L varies discretely from 1 xi(0) to 8 xi(0).The time dependent Ginzburg-Landau (TDGL) equations approach is used upon taking the order parameter and the local magnetic field invariant along the z-direction. The vortex configurations at the equilibrium can be obtained from the TDGL equations for superconductivity as the system relaxes to the stationary state.The obtained results show that the limit of vortex penetration is for the square sample of size 3 xi(0) x 3 xi(0) in which only a single vortex are allowed into the sample. For smaller specimens, no vortex can be formed and the field entrance into the sample is continuous and the total flux penetration occurs at higher values of H/H-c2(0), where H-c2(T) is the upper critical field. Otherwise, for larger samples different vortices patterns can be observed depending on the sample size. (c) 2007 Elsevier B.V. All rights reserved.

Fermions bounded by kinks of false vacuum models

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

AC Conductivity and Impedance Properties of 0.65Pb(Mg1/3Nb2/3)O-3-0.35PbTiO(3) Ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Abelian-Higgs and vortices from ABJM: towards a string realization of AdS/CMT

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Magnetic flux inversion in charged BPS vortices in a Lorentz-violating Maxwell-Higgs framework

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analog Model for Quantum Gravity Effects: Phonons in Random Fluids

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Percolation of Monte Carlo clusters

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SUBSTITUTIONAL DONOR RELATED STATES AND AU/GE/NI CONTACTS TO ALXGA1-XAS

Current-voltage measurements performed on bulk AlxGa1-xAs equipped with Au/Ge/Ni contacts reveal surprising deviations from ohmic behaviour when the temperature is lowered to that of liquid nitrogen. Significant differences are observed between samples with x = 0.3 (direct band-gap material) and x = 0.5 (indirect band-gap material). The dominant states of the donor atoms Si (doping) or Ge are found to be responsible for such behaviour. Evidence for the existence of an effective-mass X-valley metastable state is also presented.

Relaxation and tunnelling of structural units within the LTO phase of La2CuO4

The anelastic relaxation (elastic energy loss and Young modulus) of nearly stoichiometric La2CuO4+delta with LTO structure was measured. Extraordinarily intense effects are present below room temperature in the elastic dynamic susceptibility, indicating relaxational dynamics of a relevant fraction of the lattice. The involved degrees of freedom are identified as rotations of the CuO6 octahedra. Two distinct processes are found at frequencies around 1 kKz: one is observed around 150 K and is characterized by a mean activation energy of 2800 K; the second one occurs below 30 K and is governed by atomic tunnelling. Two explanations are proposed for the faster process: i) formation of fluctuating LTT domains on a scale of few atomic cells; ii) the LTO phase is a dynamical Jahn-Teller phase with all the octahedra tunneling between two LTT-like tilts. In both cases there would be important implications regarding the mechanisms giving rise to charge nanophase separation and strong electron-phonon coupling.

Spectroscopic properties and upconversion mechanisms in Er3+-doped fluoroindate glasses

Fluorindate glasses containing 1,2,3,4 ErF3 mol % were prepared in a dry box under argon atmosphere. Absorption, Stokes luminescence (under visible and infrared excitation), the dependence of 4S3/2, 4I11/2, and 4I13/2 lifetimes with Er concentration, and upconversion under Ti-saphire laser excitation at λ=790 nm were measured, mostly at T=77 and 300 K. The upconversion results in a strong green emission and weaker blue and red emissions whose intensity obeys a power-law behavior I∼Pn, where P is the infrared excitation power and n=1.6, 2.1, and 2.9 for the red, green, and blue emissions, respectively. The red emission exponent n=1.5 can be explained by a cross relaxation process. The green and blue emissions are due to excited state absorption (ESA) and energy transfer (ET) processes that predict a factor n=2 and n=3 for the green and blue emissions, respectively. From transient measurements we concluded that for lightly doped samples the green upconverted emission is originated due to both processes ESA and ET. However, for heavily doped samples ET is the dominant process.