Real Time Analysis of Thermal Activation via Sphaleron Transitions

We study the process of thermal activation mediated by sphaleron transitions by analyzing the real-time dynamics of the decay out of equilibrium in a $1+1$ dimensional field theory with a metastable state. The situation considered is that of a rapid supercooling in which the system is trapped in a metastable state at a temperature larger than the mass of the quanta, but smaller than the energy to create a critical droplet. The initial density matrix is evolved in time and the nucleation rate (probability current at the saddle point) is computed. The nucleation rate is {\it time dependent}, vanishing at early times, reaching a maximum at a time $t \approx 1/m$ with $m$ the mass of quanta in the metastable state, and decreasing at long times as a consequence of unitarity. An estimate for the average number of particles of ``true vacuum'' produced as a function of time during the nucleation process is obtained.Comment: 26 pages 6 figures (available upon request), PITT-93-06, LATE

The Compressibility of Minimal Lattice Knots

The (isothermic) compressibility of lattice knots can be examined as a model of the effects of topology and geometry on the compressibility of ring polymers. In this paper, the compressibility of minimal length lattice knots in the simple cubic, face centered cubic and body centered cubic lattices are determined. Our results show that the compressibility is generally not monotonic, but in some cases increases with pressure. Differences of the compressibility for different knot types show that topology is a factor determining the compressibility of a lattice knot, and differences between the three lattices show that compressibility is also a function of geometry.Comment: Submitted to J. Stat. Mec

Renormalization Group Study of Chern-Simons Field Coupled to Scalar Matter in a Modified BPHZ Subtraction Scheme

We apply a soft version of the BPHZ subtraction scheme to the computation of two-loop corrections from an Abelian Chern-Simons field coupled to (massive) scalar matter with a $\lambda(\Phi^\dag\Phi)^2$ and $\nu(\Phi^\dag\Phi)^3$ self-interactions. The two-loop renormalization group functions are calculated. We compare our results with those in the literature.Comment: 15 pages, 7 figures, revtex. To appear in Phys. Rev.

The Exact Critical Bubble Free Energy and the Effectiveness of Effective Potential Approximations

To calculate the temperature at which a first-order cosmological phase transition occurs, one must calculate $F_c(T)$, the free energy of a critical bubble configuration. $F_c(T)$ is often approximated by the classical energy plus an integral over the bubble of the effective potential; one must choose a method for calculating the effective potential when $V''<0$. We test different effective potential approximations at one loop. The agreement is best if one pulls a factor of $\mu^4/T^4$ into the decay rate prefactor [where $\mu^2 = V''(\phi_f)$], and takes the real part of the effective potential in the region $V''<0$. We perform a similar analysis on the 1-dimensional kink.Comment: 11 pages plus 3 figures in jyTeX; CALT-68-188

A Factorization Law for Entanglement Decay

We present a simple and general factorization law for quantum systems shared by two parties, which describes the time evolution of entanglement upon passage of either component through an arbitrary noisy channel. The robustness of entanglement-based quantum information processing protocols is thus easily and fully characterized by a single quantity.Comment: 4 pages, 5 figure

Variabilidade genética para os teores de proteínas, ferro e zinco em genótipos de feijão-caupi.

O objetivo deste trabalho foi avaliar a variabilidade genética para os teores de proteínas, ferro e zinco em 24 genótipos de feijão-caupi. O experimento foi conduzido no município de Teresina-PI, no período de setembro a dezembro de 2017, em delineamento de blocos completos casualizados, com duas repetições. Foram realizadas análises de variância e as médias agrupadas pelo teste de Tocher

BRS Energia.

bitstream/CNPA/19902/1/Folder_brs_energia.pd

Potencial de linhagens elite de feijão-caupi das subclasses comerciais sempre-verde e mulato no município de Ipiranga, PI.

Este trabalho objetivou verificar a variabilidade genética existente entre linhagens de feijão-caupi das subclasses comercias sempre-verde e mulato e selecionar aquelas com melhores características agronômicas e adaptadas às condições edafoclimáticas de Ipiranga, PI. Foram avaliados 14 genótipos, compreendendo 12 linhagens e duas cultivares comerciais

Selection of superior cowpea lines for multi-traits and adaptabilities to the Piauí semi-arid using genotype by yield*trait biplot analysis.

Cowpea is a great socioeconomically important leguminous plant worldwide. The crop is an excellent source of proteins and minerals, mainly for the poorest populations. It is cultivated in some states of Brazil. The Piauí semi-arid is the most yielding zone in the state. Thus, the selection of superior cowpea genotypes for multi-traits and adaptabilities to this growing area is very important for the small-scale and medium-scale farmers in Piauí. The objective of this study was to select the superior cowpea lines for their multitraits and adaptabilities to the Piauí semi-arid zone based on the genotype by the yield*trait (GYT) Biplot approach. Seventeen elite lines and three cultivars were evaluated in a randomized complete block design with four replications under the rainfed growing condition at three different locations away from the Piauí semi-arid zone