Spin-Charge Separation at Finite Temperature in the Supersymmetric t-J Model with Long-Range Interactions

Thermodynamics is derived rigorously for the 1D supersymmetric {\it t-J} model and its SU($K,1$) generalization with inverse-square exchange. The system at low temperature is described in terms of spinons, antispinons, holons and antiholons obeying fractional statistics. They are all free and make the spin susceptibility independent of electron density, and the charge susceptibility independent of magnetization. Thermal spin excitations responsible for the entropy of the SU($K,1$) model are ascribed to free para-fermions of order $K-1$.Comment: 10 pages, REVTE

Green Function of the Sutherland Model with SU(2) internal symmetry

We obtain the hole propagator of the Sutherland model with SU(2) internal symmetry for coupling parameter $\beta=1$, which is the simplest nontrivial case. One created hole with spin down breaks into two quasiholes with spin down and one quasihole with spin up. While these elementary excitations are energetically free, the form factor reflects their anyonic character. The expression for arbitrary integer $\beta$ is conjectured.Comment: 13pages, Revtex, one ps figur

Derivation of the particle dynamics from kinetic equations

We consider the microscopic solutions of the Boltzmann-Enskog equation discovered by Bogolyubov. The fact that the time-irreversible kinetic equation has time-reversible microscopic solutions is rather surprising. We analyze this paradox and show that the reversibility or irreversibility property of the Boltzmann-Enskog equation depends on the considered class of solutions. If the considered solutions have the form of sums of delta-functions, then the equation is reversible. If the considered solutions belong to the class of continuously differentiable functions, then the equation is irreversible. Also, we construct the so called approximate microscopic solutions. These solutions are continuously differentiable and they are reversible on bounded time intervals. This analysis suggests a way to reconcile the time-irreversible kinetic equations with the time-reversible particle dynamics. Usually one tries to derive the kinetic equations from the particle dynamics. On the contrary, we postulate the Boltzmann-Enskog equation or another kinetic equation and treat their microscopic solutions as the particle dynamics. So, instead of the derivation of the kinetic equations from the microdynamics we suggest a kind of derivation of the microdynamics from the kinetic equations.Comment: 18 pages; some misprints have been corrected, some references have been adde

Foreword

This work reports on the performances of ohmic contacts fabricated on highly p-type doped 4H-SiC epitaxial layer selectively grown by vapor-liquid-solid transport. Due to the very high doping level obtained, the contacts have an ohmic behavior even without any annealing process. Upon variation of annealing temperatures, it was shown that both 500 and 800 °C annealing temperature lead to a minimum value of the Specific Contact Resistance (SCR) down to 1.3×10−6 Ω⋅cm2. However, a large variation of the minimum SCR values has been observed (up to 4×10−4 Ω⋅cm2). Possible sources of this fluctuation have been also discussed in this paper

Influence of carbon number of C1–C7 hydrocarbons on PAH formation

The influence of carbon number of seven hydrocarbons (methane, ethane, propane, n-butane, i-butane, heptane and toluene) on PAH formation was investigated in a laminar tube reactor. The hydrocarbons underwent oxygen-free pyrolysis within the temperature range of 1050–1350 °C at a fixed carbon concentration of 10,000 ppm on C 1 basis. Particulate and gas phase PAHs were collected at the outlet of the reactor at pyrolysis temperature intervals of 100 °C. The particulates generated were characterised at sub-micron levels in terms of size, number and mass using a differential mobility spectrometer (DMS-500). PAHs from both the gas and particulate samples were extracted using an accelerated solvent extractor (ASE) and the extracts analysed using gas chromatography coupled to mass spectrometry (GCMS). The PAHs studied were the US EPA 16 priority PAHs with particular attention given to group B2, which are possible human carcinogens. The experimental results showed that increase in temperature of the reactor from 1050 to 1350 °C decreased the total PAH concentrations regardless of the carbon number of the hydrocarbon investigated. Increasing the carbon number of C 1 –C 7 hydrocarbons decreased the gas phase (GP) PAH concentrations at a temperature of 1350 °C, while the particulate phase (PP) PAH concentrations (as well as those of Group B2 PAHs) decreased at a temperature of 1150 °C. There was increasing and decreasing trends of total PAH concentrations with increasing carbon number of the hydrocarbons at temperatures of 1050 °C and 1350 °C respectively. Benzenoid and five-membered ring PAHs of 2–4 rings were detected in roughly similar concentrations irrespective of the carbon number of the hydrocarbon. Soot propensities, abundance of particle phase PAHs and carcinogenicity of soot particles increased substantially at a temperature of 1050 °C due to isomerisation in the case of the C 4 hydrocarbons and aromatisation in the case of C 7 hydrocarbons. PAHs from toluene and propane had the highest weighted carcinogenicities at a temperature of 1050 °C per unit volume of gas and per unit soot mass respectively. The weighted carcinogenicity (soot mass basis) decreased with increasing carbon number at temperature of 1150 °C. Potential implication of these observations is that hydrocarbons known to produce substantial particulate mass in combustion systems such as an internal combustion engines, could also have low toxicity

Human Resource Outsourcing: Lesson From Multinational Enterprises

This paper examines the consequence of the organization internalization on the practice of human resource (HR) outsourcing among manufacturing organizations. The assumption is that HR outsourcing is perceived as an innovative practice and that multinational enterprise (MNEs) will employ this practice more than local organizations. The data was gathered from survey questionnaires of 232 manufacturing organizations. Of the sample, 113 organizations engaged with HR outsourcing, and 71 are MNEs that partially outsource their HR functions. The findings reveal that HR outsourcing among MNEs is used to a greater extent than local organizations. A significant difference is found in the extent of outsourcing payroll, benefits, training and recruitment between MNEs and in local organizations

A well-posedness theory in measures for some kinetic models of collective motion

We present existence, uniqueness and continuous dependence results for some kinetic equations motivated by models for the collective behavior of large groups of individuals. Models of this kind have been recently proposed to study the behavior of large groups of animals, such as flocks of birds, swarms, or schools of fish. Our aim is to give a well-posedness theory for general models which possibly include a variety of effects: an interaction through a potential, such as a short-range repulsion and long-range attraction; a velocity-averaging effect where individuals try to adapt their own velocity to that of other individuals in their surroundings; and self-propulsion effects, which take into account effects on one individual that are independent of the others. We develop our theory in a space of measures, using mass transportation distances. As consequences of our theory we show also the convergence of particle systems to their corresponding kinetic equations, and the local-in-time convergence to the hydrodynamic limit for one of the models

Renormalized Harmonic-Oscillator Description of Confined Electron Systems with Inverse-Square Interaction

An integrable model for SU($\nu$) electrons with inverse-square interaction is studied for the system with confining harmonic potential. We develop a new description of the spectrum based on the {\it renormalized harmonic-oscillators} which incorporate interaction effects via the repulsion of energy levels. This approach enables a systematic treatment of the excitation spectrum as well as the ground-state quantities.Comment: RevTex, 7 page

Exactly Solvable Pairing Model Using an Extension of Richardson-Gaudin Approach

We introduce a new class of exactly solvable boson pairing models using the technique of Richardson and Gaudin. Analytical expressions for all energy eigenvalues and first few energy eigenstates are given. In addition, another solution to Gaudin's equation is also mentioned. A relation with the Calogero-Sutherland model is suggested.Comment: 9 pages of Latex. In the proceedings of Blueprints for the Nucleus: From First Principles to Collective Motion: A Festschrift in Honor of Professor Bruce Barrett, Istanbul, Turkey, 17-23 May 200

Size dependent line broadening in the emission spectra of single GaAs quantum dots: Impact of surface charges on spectral diffusion

Making use of droplet epitaxy, we systematically controlled the height of self-assembled GaAs quantum dots by more than one order of magnitude. The photoluminescence spectra of single quantum dots revealed the strong dependence of the spectral linewidth on the dot height. Tall dots with a height of ~30 nm showed broad spectral peaks with an average width as large as ~5 meV, but shallow dots with a height of ~2 nm showed resolution-limited spectral lines (<120 micro eV). The measured height dependence of the linewidths is in good agreement with Stark coefficients calculated for the experimental shape variation. We attribute the microscopic source of fluctuating electric fields to the random motion of surface charges at the vacuum-semiconductor interface. Our results offer guidelines for creating frequency-locked photon sources, which will serve as key devices for long-distance quantum key distribution.Comment: 6 pages, 6 figures; updated figs and their description