Second Order Gauge Theory

A gauge theory of second order in the derivatives of the auxiliary field is constructed following Utiyama's program. A novel field strength $G=\partial F+fAF$ arises besides the one of the first order treatment, $F=\partial A-\partial A+fAA$. The associated conserved current is obtained. It has a new feature: topological terms are determined from local invariance requirements. Podolsky Generalized Eletrodynamics is derived as a particular case in which the Lagrangian of the gauge field is $L_{P}\propto G^{2}$. In this application the photon mass is estimated. The SU(N) infrared regime is analysed by means of Alekseev-Arbuzov-Baikov's Lagrangian.Comment: 27 pages. No figure. Final versio

Bulk viscosity driving the acceleration of the Universe

The possibility that the present acceleration of the universe is driven by a kind of viscous fluid is exploited. At background level this model is similar to the generalized Chaplygin gas model (GCGM). But, at perturbative level, the viscous fluid exhibits interesting properties. In particular the oscillations in the power spectrum that plagues the GCGM are not present. Possible fundamental descriptions for this viscous dark energy are discussed.Comment: Latex file, 8 pages, 3 eps figure

Gastric content technique collection for in vitro degradation and gas production in horses supplemented with live yeast and protected yeast

ABSTRACT Due to the difficulty in acessing certain sites of fermentation and possible starch digestion, studies show the need for equine gastric digestive fisiology evaluation. The aim of this experiment was to assess horses supplemented with live yeast and protected live yeast (Saccharomyces cerevisae NCYC Sc 47) to validate a new procedure of gastric content collection for determination of pH, latic acid, short chain fatty acids and gas production and degradation to be used in further in vitro fermentative studies. The experimental design used was a the latin square (4x4) for 4 periods and 1 day of gastric content collection, with 15 days of rest between it. The groups were divided in control (CTRL), non protected live yeast (NPYEA), protected live yeast (PYEA) and a combination of live yeast + protected yeast (COMB). Treatment means were compared using orthogonal contrasts (C1: CTRL versus NPYEA, PYEA and COMB; C2: COMB versus NPYEA and PYEA; C3: NPYEA versus PYEA) and Tukey´s test was used at a 5% significance level. The procedure was highly tolerated and provided great accuracy of the collection site. The live yeast supplementation increased the concentration of acetic acid at the horses’ stomachs. When gastric content was used as inoculum for in vitro fermentation, the protected live yeast produced less gas