Quasinormal modes and thermodynamical aspects of the 3D Lifshitz black hole

We consider scalar and spinorial perturbations on a background described by a $z=3$ three-dimensional Lifshitz black hole. We obtained the corresponding quasinormal modes which perfectly agree with the analytical result for the quasinormal frequency in the scalar case. The numerical results for the spinorial perturbations reinforce our conclusion on the stability of the model under these perturbations. We also calculate the area spectrum, which prove to be equally spaced, as an application of our results.Comment: 8 pages, 5 figures. Prepared for "Recent Developments in Gravity (NEB XV)", Chania, Greece, 20-23 June 201

Latin American perspectives and the IT2017 curricular guidelines

The term information technology has many meanings for various stakeholders and continues to evolve. This discussion presents an overview of the developing curricular guidelines for rigorous, high quality, bachelor\u27s degree programs in information technology (IT), called IT2017. Panel participants will focus on Latin American academic and industry perspectives on IT undergraduate education. Discussion will seek to ascertain commonalities and differences between the current draft IT2017 report and perspectives from Latino/a professional and academic communities. It also addresses ways in which this endeavor contrasts with current practices in Latin America industry and academia

Instability of the Time Dependent Horava-Witten Model

We consider scalar perturbations in the time-dependent Ho\u{r}ava-Witten Model in order to probe its stability. We show that during the non-singular epoque the model evolves without instabilities until it encounters the curvature singularity where a big crunch is supposed to occur. We compute the frequencies of the scalar field oscillation during the stable period and show how the oscillations can be used to prove the presence of such a singularity.Comment: 12 pages, 4 figures. References added. Some comments clarified. Accepted in Phys. Rev.

Perturbations of Gauss-Bonnet Black Strings in Codimension-2 Braneworlds

We derive the Lichnerowicz equation in the presence of the Gauss-Bonnet term. Using the modified Lichnerowicz equation we study the metric perturbations of Gauss-Bonnet black strings in Codimension-2 Braneworlds.Comment: 26 pages, no figures, clarifying comments and one reference added, to be published in JHE

Two-dimensional topological insulator state in cadmium arsenide thin films

Two-dimensional topological insulators (2D TIs) are a highly desired quantum phase but few materials have demonstrated clear signatures of a 2D TI state. It has been predicted that 2D TIs can be created from thin films of three-dimensional TIs by reducing the film thickness until the surface states hybridize. Here, we employ this technique to report the first observation of a 2D TI state in epitaxial thin films of cadmium arsenide, a prototype Dirac semimetal in bulk form and a 3D TI in thin films. Using magnetotransport measurements with electrostatic gating, we observe a Landau level spectrum and quantum Hall effect that are in excellent agreement with those of an ideal 2D TI. Specifically, we observe a crossing of the zeroth Landau levels at a critical magnetic field. We show that the film thickness can be used to tune the critical magnetic field. Moreover, a larger change in film thickness causes a transition from a 2D TI to a 2D trivial insulator, just as predicted by theory. The high degree of tunability available in epitaxial cadmium arsenide heterostructures can thus be used to fine-tune the 2D TI, which is essential for future topological devices.Comment: Accepted for publication in Physical Review Letters. Fixed issues with the display of Fig. 3 in the pdf in this versio

Stability Analysis and Area Spectrum of 3-Dimensional Lifshitz Black Holes

In this work, we probe the stability of a $z=3$ three-dimensional Lifshitz black hole by using scalar and spinorial perturbations. We found an analytical expression for the quasinormal frequencies of the scalar probe field, which perfectly agree with the behavior of the quasinormal modes obtained numerically. The results for the numerical analysis of the spinorial perturbations reinforce the conclusion of the scalar analysis, i.e., the model is stable under scalar and spinor perturbations. As an application we found the area spectrum of the Lifshitz black hole, which turns out to be equally spaced.Comment: 23 pages, 6 figures. References added. Version to appear in Phys. Rev.

Shortcuts in a Nonlinear Dynamical Braneworld in Six Dimensions

We consider a dynamical brane world in a six-dimensional spacetime containing a singularity. Using the Israel conditions we study the motion of a 4-brane embedded in this setup. We analyse the brane behaviour when its position is perturbed about a fixed point and solve the full nonlinear dynamics in the several possible scenarios. We also investigate the possible gravitational shortcuts and calculate the delay between graviton and photon signals and the ratio of the corresponding subtended horizons.Comment: 26 pages, 9 figures. References and discussion added. Title changed to match the version accepted in Class. and Quant. Gra

Age, growth and reproduction of Diplodus sargus Linnaeus, 1758 (Sparidae) north of Spain

Monthly samples of Diplodus sargus Linnaeus, 1758 taken north of Spain over one year were used to describe age, growth, annual cycle in condition factor and reproduction. Results indicate that the greatest absolute increase in length was in the first year of life. The relative growth in length declined constantly, being less than 10% from the fifth year onwards. The equations of growth for the population are: Lt = 48.48 (1 - e-0.18(t + 0.58)) and PT= 2285.5 (1 -e0.178(t-0.58))3.014 The first spawning occurs in the third year of life (20 cm LT) in males and in the fourth year (25 cm LT) in females. The sexual ratio was: 56.7 % males, 37.7 % females and 5.6 % hermaphrodite or bisexual. Spawning took place over a period slightly longer than two months, from April to May or June. Condition is better in females than males during the spawning season; the latter spend nearly all their perintestinal fat as well as hepatic fat, during the spawning process. They recover their pre-spawning condition in summer and autumn. The fecundity estimates was 2.54 ± 152 eggs/g eviscerated fish.Se analizaron 270 ejemplares de Diplodus sargus Linnaeus, 1758 con tallas comprendidas entre 11,5 y 45 cm de longitud total (LT) capturados en el litoral asturiano entre noviembre de 1983 y octubre de 1984. Los jóvenes de menos de 21 cm habitan en el área próxima al litoral y a partir de esta talla frecuentan fondos más profundos. Las ecuaciones de crecimiento para el conjunto de la población son Lt = 48,48 (1 - e-0,18(t + 0,58)) y PT= 2285,5 (1 - e0,178(t-0,58))3,014 El mayor incremento absoluto en longitud tiene lugar durante el primer año de vida y el crecimiento relativo declina constantemente hasta constituir el 10%, respecto al año anterior; a partir del quinto año. La freza tiene lugar entre abril y junio. La condición de los machos es más baja que la de las hembras en los meses de freza y posteriores a la misma, dado que no sólo agotan la grasa perintestinal sino también gran parte de la hepática; la recuperación ocurre en verano y otoño. La primera maduración tiene lugar a partir del tercer año de vida (20 cm LT) en los machos y cuarto año (25 cm LT) en las hembras. La proporción sexual encontrada en individuos de más de 20 cm LT fue 56,7% machos, 37,7 % hembras y 5,6% individuos en proceso de transformación que presentan gónadas masculinas y femeninas simultáneamente. La fecundidad media calculada para individuos entre 33,5 y 44 cm LT fue de 254,4 ± 152 huevos por gramo de pez eviscerado.Instituto Español de Oceanografí