Towards SDp-brane Quantization

The quantum mechanical analysis of the canonical hamiltonian description of the effective action of a SDp-brane in bosonic ten dimensional Type II supergravity in a homogeneous background is given. We find exact solutions for the corresponding quantum theory by solving the Wheeler-deWitt equation in the late-time limit of the rolling tachyon. The probability densities for several values of p are shown and their possible interpretation is discussed. In the process the effects of electromagnetic fields are also incorporated and it is shown that in this case the interpretation of tachyon regarded as ``matter clock'' is modified.Comment: 15 pages, 3 eps figures, revtex

Twisted Covariant Noncommutative Self-dual Gravity

A twisted covariant formulation of noncommutative self-dual gravity is presented. The formulation for constructing twisted noncommutative Yang-Mills theories is used. It is shown that the noncommutative torsion is solved at any order of the $\theta$-expansion in terms of the tetrad and some extra fields of the theory. In the process the first order expansion in $\theta$ for the Pleba\'nski action is explicitly obtained.Comment: 23+1 pages, no figures, corrected typos, references and Appendix B is adde

Crossing the phantom divide in an interacting generalized Chaplygin gas

Unified generalized Chaplygin gas models assuming an interaction between dark energy and dark matter fluids have been previously proposed. Following these ideas, we consider a particular relation between dark densities, which allows the possibility of a time varying equation of state for dark energy that crosses the phantom divide at a recent epoch. Moreover, these densities decay during all the evolution of the Universe, avoiding a Big Rip. We find also a scaling solution, i.e. these densities are asymptotically proportional in the future, which contributes to the solution of the coincidence problem.Comment: Improved version, 10 pages, 4 figures, References adde

Size, Age, and Spatial-Temporal Distribution of Shortfin Mako in the Mexican Pacific Ocean

Abstract Basic population parameters such as age, size, and distribution have been poorly evaluated for the Shortfin Mako Isurus oxyrinchus in the Mexican Pacific Ocean. According to data collected by scientific observers on board medium-size fishing vessels during the period of 2006–2013, size as TL was obtained for 5,740 individual sharks. The range of TL was 70–362 cm for females and 71–296 cm for males. Weight (W), measured randomly from 1,409 individuals, ranged from 2 to 90 kg for females and from 2 to 80 kg for males. The weight-to-TL ratio was best fitted by the equation W = 4 × 10−5(TL)2.59 (r2 = 0.6532). No sex-specific difference was found in the weight-to-TL relationship between males and females, nor in W or TL separately. By using the inverse von Bertalanffy equation and parameters described by other authors for the same study area, we determined the age range for individuals captured on the basis of their TL. The age ranged from 0 to 39 years in females and from 0 to 21 years in males. Using a logistic model, the mean length at sexual maturity was obtained for 2,532 males (TL = 190 cm). The quarterly distribution of young of the year and 1-year-old juveniles showed that there is a tendency for these sharks to mov

Determination of Lmax for Atlantic Bluefin Tuna, Thunnus thynnus (L.), from Meta-Analysis of Published and Available Biometric Data

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