Rapid Thermalization in Field Theory from Gravitational Collapse

Motivated by the duality with thermalization in field theory, we study gravitational collapse of a minimally coupled massless scalar field in Einstein gravity with a negative cosmological constant. We investigate the system numerically and establish that for small values of the initial amplitude of the scalar field there is no black hole formation, rather, the scalar field performs an oscillatory motion typical of geodesics in AdS. For large enough values of the amplitude of the scalar field we find black hole formation which we detect numerically as the emergence of an apparent horizon. Using the time of formation as an estimate for thermalization in the field theory we conclude that thermalization occurs very rapidly, close to the causal bound for a very wide range of black hole masses. We further study the thermalization time in more detail as a function of the amplitude and the width of the initial Gaussian scalar field profile and detect a rather mild structure.Comment: 5 pages, 4 figures. v2: References added, improved most grids by a factor of 8, main results unchanged. v3 PRD versio

La liberación inmediata de buques en procedimientos de medidas provisionales. ¿Nuevas tendencias y desafíos?

This article discusses the incidents and situations created when vessels are detained in foreign ports, and the measures that need to be undertaken to overcome these disputes, analyzing the United Nations Convention on the Law of the Sea; that not only provides a frame that all States (who have submitted) should constrain to, but also contributes to define the peaceful means for settlements intended to overcome such controversial situations. Apart from the consideration of all these regulations, jurisprudence and real precedents are explored. In first place, to perceive the way parties react towards these situations, and also to understand how the settlement of disputes be operationalized through the International Tribunal for the Law of the Sea. For this purpose, contemporary cases such as the Grand Prince, the ARA Libertad, and the Artic Sunrise are deepened.En el presente artículo se ven plasmados los incidentes que pueden presentarse cuando los buques y sus tripulaciones son detenidos en puertos extranjeros, y las distintas medidas a tomar ante estas controversias, analizando la Convención de las Naciones Unidas sobre el Derecho del Mar, que no solo provee una regulación marco a la que todos los Estados signatarios deben adecuarse, sino que también contribuye con la enunciación de las distintas formas de solución pacífica creadas para superar estas situaciones. Además de considerar estas regulaciones, es necesario analizar la jurisprudencia al respecto. En primer lugar, ya que ayuda a visualizar la forma en que los Estados actúan frente a estas situaciones y asimismo para comprender cómo el sistema de solución de controversias ha sido llevado a la práctica por el Tribunal de Hamburgo. Con esa finalidad profundizamos sobre algunos casos contemporáneos como el Grand Prince, el ARA Libertad y el Artic Sunrise

Shocks near Jamming

Non-linear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they jam, these fragile and disordered solids exhibit a vanishing rigidity and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are dynamically compressed, and demonstrate that the elementary excitations are strongly non-linear shocks, rather than ordinary phonons. We capture the full dependence of the shock speed on pressure and impact intensity by a surprisingly simple analytical model.Comment: Revised version. Accepted for publication in Phys. Rev. Let

Discovery of a Galaxy Cluster in the Foreground of the Wide-Separation Quasar Pair UM425

We report the discovery of a cluster of galaxies in the field of UM425, a pair of quasars separated by 6.5arcsec. Based on this finding, we revisit the long-standing question of whether this quasar pair is a binary quasar or a wide-separation lens. Previous work has shown that both quasars are at z=1.465 and show broad absorption lines. No evidence for a lensing galaxy has been found between the quasars, but there were two hints of a foreground cluster: diffuse X-ray emission observed with Chandra, and an excess of faint galaxies observed with the Hubble Space Telescope. Here we show, via VLT spectroscopy, that there is a spike in the redshift histogram of galaxies at z=0.77. We estimate the chance of finding a random velocity structure of such significance to be about 5%, and thereby interpret the diffuse X-ray emission as originating from z=0.77, rather than the quasar redshift. The mass of the cluster, as estimated from either the velocity dispersion of the z=0.77 galaxies or the X-ray luminosity of the diffuse emission, would be consistent with the theoretical mass required for gravitational lensing. The positional offset between the X-ray centroid and the expected location of the mass centroid is about 40kpc, which is not too different from offsets observed in lower redshift clusters. However, UM425 would be an unusual gravitational lens, by virtue of the absence of a bright primary lensing galaxy. Unless the mass-to-light ratio of the galaxy is at least 80 times larger than usual, the lensing hypothesis requires that the galaxy group or cluster plays a uniquely important role in producing the observed deflections. Based on observations performed with the Very Large Telescope at the European Southern Observatory, Paranal, Chile.Comment: 12 pages, accepted by ApJ 2005, May 1

History of Jose Vasquez Borrego Grant

Typed Spanish and English translations of ...the history of the settlement on certain lands on the bank of the Rio del Norte by Jose Basquez Borrego... by C. Alegria in 1930. Donated by Hubert J. Miller. NOTE: The file does not contain facsimiles of the original manuscripts.https://scholarworks.utrgv.edu/lrgv/1024/thumbnail.jp