Heat kernel methods for Lifshitz theories

We study the one-loop covariant effective action of Lifshitz theories using the heat kernel technique. The characteristic feature of Lifshitz theories is an anisotropic scaling between space and time. This is enforced by the existence of a preferred foliation of space-time, which breaks Lorentz invariance. In contrast to the relativistic case, covariant Lifshitz theories are only invariant under diffeomorphisms preserving the foliation structure. We develop a systematic method to reduce the calculation of the effective action for a generic Lifshitz operator to an algorithm acting on known results for relativistic operators. In addition, we present techniques that drastically simplify the calculation for operators with special properties. We demonstrate the efficiency of these methods by explicit applications.Comment: 36 pages, matches journal versio

Aportaciones de la Técnica de Rejilla en la comprensión de los trastornos alimentarios

El objetivo de investigación fue identificar características estructurales y de contenido del sistema de constructos de hijas diagnosticadas con trastornos de conducta alimentaria y de sus madres. En este estudio descriptivo, se aplicó a 14 hijas, de 18 a 29 años, y madres, técnica de rejilla interpersonal y entrevista focalizada. En los resultados destaca que el 70% de hijas y la totalidad de madres presentan rigidez cognitiva. En el contenido de los constructos de autodefinición de las hijas destacan aspectos emocionales y en las madres, aspectos personales. Los contenidos de los constructos discrepantes de ambas, se agrupan en aspectos emocionales. En los dilemas implicativos se presenta con mayor frecuencia la búsqueda de autonomía/autoafimación que implica abandono de los demás

Ligand sequential replacement on chromium(III)-aqua complexes by L-alanine and other biological amino acids: a kinetic perspective

The ligand sequential replacement on chromium(III)-aqua complexes by L-alanine in slightly acidic aqueous solutions (pH range: 3.55-5.61) has been kinetically followed by means of UV-Vis spectrophotometry. A two rate constant model has been applied to fit the absorbance-time data, corresponding to the formation (k1) and decay (k2) of an intermediate not reactive enough to be in steady state (long-lived intermediate). The kinetic orders of the amino acid were fractional (0.40 ± 0.03 for k1 and 0.40 ± 0.02 for k2). The two steps showed base catalysis, and the activation energies were 60 ± 3 (for k1) and 83 ± 6 (for k2) kJ mol-1. The rate constants for the coordination of the first L-alanine ligand followed the sequence CrOH2+ < Cr(OH)2+ < Cr(OH)3, Cr3+ being almost inactive. This suggests that the increase in the reaction rate with increasing pH was caused by the enhancement of the lability of the Cr(III)-aqua bonds induced by the presence of hydroxo ligands. The activation parameters for a series of ligand substitution on Cr(III)-aqua complexes by organic molecules yielded a statistically significant enthalpy-entropy linear plot with an isokinetic temperature of 296 ± 21 K