Vortex Production in a First Order Phase-Transition at Finite Temperature

We simulate the production of vortices in a first order phase transition at finite temperature. The transition is carried out by randomly nucleating critical bubbles and the effects of thermal fluctuations (which could be relevant for vortex production) are represented by randomly nucleating subcritical bubbles. Our results show that the presence of subcritical bubbles suppresses vortices with clear and prominent profiles, though net number of vortices is consistent with theoretical estimates. We also determine the typical speed of vortices arising due to randomness associated with the phase transition to be about 0.5.Comment: 10 pages, in LATEX, 6 figures (not included

The Energy Density in the Maxwell-Chern-Simons Theory

A two-dimensional nonrelativistic fermion system coupled to both electromagnetic gauge fields and Chern-Simons gauge fields is analysed. Polarization tensors relevant in the quantum Hall effect and anyon superconductivity are obtained as simple closed integrals and are evaluated numerically for all momenta and frequencies. The correction to the energy density is evaluated in the random phase approximation (RPA), by summing an infinite series of ring diagrams. It is found that the correction has significant dependence on the particle number density. In the context of anyon superconductivity, the energy density relative to the mean field value is minimized at a hole concentration per lattice plaquette (0.05 \sim 0.06) (p_c a/\hbar)^2 where p_c and a are the momentum cutoff and lattice constant, respectively. At the minimum the correction is about -5 % \sim -25 %, depending on the ratio (2m \omega_c)/(p_c^2) where \omega_c is the frequency cutoff. In the Jain-Fradkin-Lopez picture of the fractional quantum Hall effect the RPA correction to the energy density is very large. It diverges logarithmically as the cutoff is removed, implying that corrections beyond RPA become important at large momentum and frequency.Comment: 19 pages (plain Tex), 12 figures not included, UMN-TH-1246/9

Conservatism flow and the pricing of credit risk

I study the relation between the pricing of credit default swaps (CDSs) and three recently proposed firm-year measures of conditional conservatism or conservatism flow: asymmetric timeliness of earnings, asymmetric behavior of accruals, and conservatism ratio. Using CDS pricing data from Fitch, I show that there is a negative association between CDS price with maturities from one to ten years, and the first two metrics of conservatism flow. I also document that the strength of the association decreases as maturity increases. My results are consistent with the hypothesis that managers practicing timely accounting recognition of economic losses, tend to avoid ex ante negative NPV projects and more quickly abandon projects that turn out to be negative NPV ex post. These, in turn, lead to an association with CDS price, via a reduction of information asymmetry between firm insiders and outsiders, the provision of a reliable estimate of future firm wealth, and a reduction in probability of bankruptcy. I also show that the effect of asymmetric timeliness is incremental to the book-to-tax ratio, which is thought to be a measure of conservatism by the literature on taxation

Aluminum nitride-single walled carbon nanotube nanocomposite with superior electrical and thermal conductivities

Development of aluminum nitride (AlN)-single walled carbon nanotube (SWCNT) ceramic-matrix composite containing 1-6 vol% SWCNT by hot pressing has been reported in this article. The composites containing 6 vol% SWCNT are dense (similar to 99% relative density) and show high dc electrical conductivity (200 Sm-1) and thermal conductivity (62 Wm(-1) K-1) at room temperature. SWCNTs contain mostly metallic variety tubes obtained by controlled processing of the pristine tubes before incorporation into the ceramic matrix. Raman spectroscopy and field emission scanning electron microscopy (FESEM) of the fracture surface of the samples show the excellent survivability of the SWCNTs even after high-temperature hot pressing. The results indicate the possibility of preparation of AlN nanocomposite for use in plasma devices and electromagnetic shielding