Thermodynamic Properties of Generalized Exclusion Statistics

We analytically calculate some thermodynamic quantities of an ideal $g$-on gas obeying generalized exclusion statistics. We show that the specific heat of a $g$-on gas ($g \neq 0$) vanishes linearly in any dimension as $T \to 0$ when the particle number is conserved and exhibits an interesting dual symmetry that relates the particle-statistics at $g$ to the hole-statistics at $1/g$ at low temperatures. We derive the complete solution for the cluster coefficients $b_l(g)$ as a function of Haldane's statistical interaction $g$ in $D$ dimensions. We also find that the cluster coefficients $b_l(g)$ and the virial coefficients $a_l(g)$ are exactly mirror symmetric ($l$=odd) or antisymmetric ($l$=even) about $g=1/2$. In two dimensions, we completely determine the closed forms about the cluster and the virial coefficients of the generalized exclusion statistics, which exactly agree with the virial coefficients of an anyon gas of linear energies. We show that the $g$-on gas with zero chemical potential shows thermodynamic properties similar to the photon statistics. We discuss some physical implications of our results.Comment: 24 pages, Revtex, Corrected typo

Degenerate ground states and nonunique potentials: breakdown and restoration of density functionals

The Hohenberg-Kohn (HK) theorem is one of the most fundamental theorems of quantum mechanics, and constitutes the basis for the very successful density-functional approach to inhomogeneous interacting many-particle systems. Here we show that in formulations of density-functional theory (DFT) that employ more than one density variable, applied to systems with a degenerate ground state, there is a subtle loophole in the HK theorem, as all mappings between densities, wave functions and potentials can break down. Two weaker theorems which we prove here, the joint-degeneracy theorem and the internal-energy theorem, restore the internal, total and exchange-correlation energy functionals to the extent needed in applications of DFT to atomic, molecular and solid-state physics and quantum chemistry. The joint-degeneracy theorem constrains the nature of possible degeneracies in general many-body systems

Evidence of breakdown of the spin symmetry in diluted 2D electron gases

Recent claims of an experimental demonstration of spontaneous spin polarisation in dilute electron gases \cite{young99} revived long standing theoretical discussions \cite{ceper99,bloch}. In two dimensions, the stabilisation of a ferromagnetic fluid might be hindered by the occurrence of the metal-insulator transition at low densities \cite{abra79}. To circumvent localisation in the two-dimensional electron gas (2DEG) we investigated the low populated second electron subband, where the disorder potential is mainly screened by the high density of the first subband. This letter reports on the breakdown of the spin symmetry in a 2DEG, revealed by the abrupt enhancement of the exchange and correlation terms of the Coulomb interaction, as determined from the energies of the collective charge and spin excitations. Inelastic light scattering experiments and calculations within the time-dependent local spin-density approximation give strong evidence for the existence of a ferromagnetic ground state in the diluted regime.Comment: 4 pages, 4 figures, Revte

Quasiparticle Electronic structure of Copper in the GW approximation

We show that the results of photoemission and inverse photoemission experiments on bulk copper can be quantitatively described within band-structure theory, with no evidence of effects beyond the single-quasiparticle approximation. The well known discrepancies between the experimental bandstructure and the Kohn-Sham eigenvalues of Density Functional Theory are almost completely corrected by self-energy effects. Exchange-correlation contributions to the self-energy arising from 3s and 3p core levels are shown to be crucial.Comment: 4 pages, 2 figures embedded in the text. 3 footnotes modified and 1 reference added. Small modifications also in the text. Accepted for publication in PR

Flutuação populacional do ácaro-da-ferrugem-da-videira em vinhedo comercial em Candiota, RS, com diferentes métodos de amostragem.

Nos vinhedos da Região da Campanha do Rio Grande do Sul, o ácaro-da-ferrugem-da-videira, Calepitrimerus vitis (Nalepa, 1905) (Acari: Eriophyidae), tem sido encontrado com frequência desde a safra 2004/2005 associado com sintomas de bronzeamento nas folhas. A flutuação populacional de C. vitis na cultivar ?Cabernet Sauvignon? foi estudada em vinhedo comercial localizado em Candiota, RS, durante as safras agrícolas 2007/2008 (de novembro a junho) e 2008/2009 (de outubro a maio). A amostragem foi realizada nas folhas e através de armadilhas constituídas por fitas adesivas de dupla face instaladas nos ramos de produção. O pico populacional, na primeira safra, ocorreu em março de 2008 quando foram registrados 0,34 indivíduos por cm² da face abaxial das folhas medianas e 29,48 indivíduos por armadilhas. Na segunda safra, o pico populacional foi menos intenso e ocorreu em outubro de 2008, quando foram detectados 0,11 indivíduos por cm² da face abaxial das folhas medianas e 0,43 indivíduos por armadilhas. Foi detectado que o início do deslocamento de C. vitis para os locais de hibernação ocorre no verão, a partir de fevereiro. As armadilhas adesivas foram mais eficientes para identificar a presença de C. vitis no vinhedo do que a avaliação direta nas folhas. Uma correlação positiva foi encontrada entre o número de C. vitis na face abaxial das folhas e o percentual de folhas com infestação

Electron Localization in the Insulating State

The insulating state of matter is characterized by the excitation spectrum, but also by qualitative features of the electronic ground state. The insulating ground wavefunction in fact: (i) sustains macroscopic polarization, and (ii) is localized. We give a sharp definition of the latter concept, and we show how the two basic features stem from essentially the same formalism. Our approach to localization is exemplified by means of a two--band Hubbard model in one dimension. In the noninteracting limit the wavefunction localization is measured by the spread of the Wannier orbitals.Comment: 5 pages including 3 figures, submitted to PR

Quantum-Mechanical Position Operator and Localization in Extended Systems

We introduce a fundamental complex quantity, $z_{L}$, which allows us to discriminate between a conducting and non-conducting thermodynamic phase in extended quantum systems. Its phase can be related to the expectation value of the position operator, while its modulus provides an appropriate definition of a localization length. The expressions are valid for {\it any} fractional particle filling. As an illustration we use $z_{L}$ to characterize insulator to ``superconducting'' and Mott transitions in one-dimensional lattice models with infinite on-site Coulomb repulsion at quarter filling.Comment: 4 pages, REVTEX, 1 ps figure

Ab initio Study of Misfit Dislocations at the SiC/Si(001) Interface

The high lattice mismatched SiC/Si(001) interface was investigated by means of combined classical and ab initio molecular dynamics. Among the several configurations analyzed, a dislocation network pinned at the interface was found to be the most efficient mechanism for strain relief. A detailed description of the dislocation core is given, and the related electronic properties are discussed for the most stable geometry: we found interface states localized in the gap that may be a source of failure of electronic devices

Histomorphometric Analysis of the Rat Proximal Tibial Metaphysis by “Linear Scanning”

Twenty-four female Sprague-Dawley rats (10 weeks old, 200g BW) were either sham-operated (n = 6) or ovariectomized (ovx). Ovx rats were divided into 3 groups (n = 6 each) : ovx; ovx + 1,25(OH) 2D3; ovx + l,25(OH)2D3 + 1,24,25(OH)3D3. The vitamin D metabolites were fed orally starting the day after surgery. After 7 weeks all rats were sacrificed and the proximal tibiae were processed undecalcified for quantitative histomorphometry. Conventional histomorphometric analysis of the distal zone (\u3e 1 mm from the growth cartilage) of the tibial metaphysis revealed a dramatic loss of cancellous bone mass in ovx rats. Both l,25(OH)2D3 and the combination of l,25(OH)2D3 with l,24,25(OH)3D3 prevented the bone loss in the distal zone in ovx animals. Measurements in the proximal zone (\u3c 1 mm from the growth cartilage) of the tibial metaphysis were performed with a newly developed technique that utilizes the advantages of automatic image analysis, and that we propose to name linear scanning . This method revealed a significantly decreased hard tissue mass at about 100 μm and within 800 to 950 μm distance from the growth plate in ovx rats. However, ovx rats reached normal amounts of hard tissue within 250 to 450 μm from the growth plate. The results obtained by linear scanning suggest that the obvious loss of cancellous bone mass in the distal zone of the tibial metaphysis in growing ovx rats is not a consequence of structural changes in the proximal zone