The Linear Correlation Coefficient vs. the Cross Term in Bose-Einstein Correlations

We investigate the nature of the new cross term for Gaussian parameterizations of Bose-Einstein correlations of identical particles emitted from purely chaotic hadron sources formed by relativistic heavy ion collisions. We find that this additional parameter in the so-called Bertsch parameterization can be expressed in terms of a linear ``out-longitudinal'' correlation coefficient for emission of bosons and two already known ``radius'' parameters, $R_l$ and $R_o$. The linear correlation coefficient is of kinematical nature and can be used to determine the widths of longitudinal momentum distributions.Comment: 4 pages, without inclusion of the 3 figures. For PostScript file of the manuscript including the three figures goto http://t2.lanl.gov/schlei/eprint.htm

Monte Carlo Simulation of Smectic Liquid Crystals and the Electroclinic Effect: the Role of the Molecular Shape

Using Monte Carlo simulation methods, we explore the role of molecular shape in the phase behavior of liquid crystals and the electroclinic effect. We study a "bent-rod" mesogen shaped like the letter Z, composed of seven soft spheres bonded rigidly together with no intra-molecular degrees of freedom. For strongly angled molecules, we find that steric repulsion alone provides the driving force for a smectic-C phase, even without intermolecular dipole-dipole interactions. For weakly angled (nearly rod-like) molecules, we find a stable smectic-A (SmA) phase and a strong electroclinic effect with a saturation tilt angle of about 19 degrees. In the SmA phase we find evidence of vortex-like point defects. We also observe a field-induced nematic-smectic phase transition.Comment: 10 pages, including 10 postscript figures, uses REVTeX 3.0 and epsf.st

Isovector channel of quark-meson-coupling model and its effect on symmetry energy

The non-relativistic approximation of the quark-meson-coupling model has been discussed and compared with the Skyrme-Hartree-Fock model which includes spin exchanges. Calculations show that the spin-exchange interaction has important effect on the descriptions of finite nuclei and nuclear matter through the Fock exchange. Also in the quark-meson-coupling model, it is the Fock exchange that leads to a nonlinear density-dependent isovector channel and changes the density-dependent behavior of the symmetry energy.Comment: 20 pages, 9 figures and 1 table, accepted for publication in Nuclear Physics

The evolution of large-bodied theropod dinosaurs during the Mesozoic in Asia

The fossil record of large-bodied, apex carnivorous theropod dinosaurs in Eastern Asia is now among the best understood in the world, thanks to new discoveries and reinterpretations of long-neglected fossils. Asia boasts the most complete record of Middle Jurassic theropods globally, as well as one of the best-studied Late Cretaceous theropod faunas, and new research is helping to fill what was previously a 60-million-year gap in the Early-mid Cretaceous fossil record of large Asian predators. In general, the bio-geographic affinities of large-bodied Asian theropods over time were intimately related to physical geography, and progressively more derived theropod clades evolved large body size and occupied the apex predator niche throughout the Jurassic and Cretaceous. During the Middle Jurassic, largely endemic clades of basal tetanurans were prevalent in Asia, whereas during the Late Jurassic mid Cretaceous more derived “intermediate” tetanuran theropods with cosmopolitan affinities occupied the large predator role, including sinraptorids, spinosauris, and carcharodontosaurians. Finalli, during the final 20 million years of the Cretaceous, more derived, bird-like coelurosaurs attained large body size. Foremost among these were the tyrannosaurids, a radiation of northern (Asian and North American) megapredators whose ascent into the apex predator niche was a delayed event restricted to the Campanian-Masastrichian. As Asia is the focus of intense ongoing dinosaur fieldwork, our undestarnding of large-bodied theropod evolution will continue to be refined with future discoveries.El registro fósil de los dinosaurios carnívoros terópodos de gran talla en el este de Asia es uno de los mejor conocidos del mundo, gracias a nuevos descubrimientos y reinterpretaciones de fósiles que han permanecido pobremente estudiados durante mucho tiempo. Globalmente, Asia comprende el registro fósil mas completo de terópodos del Jurasico Medio, así como una de las faunas finicretácicas mejor estudiadas. Asimismo, las nuevas investigaciones están contribuyendo a completar un hiato de 60 millones de años en el registro fósil de grandes depredadores asiáticos correspondientes al Cretácico inferior-medio. En general las afinidades biogeográficas de los grandes terópodos asiáticos a través del tiempo se hallan íntimamente ligadas a la geografía física. Progresivamente, varios clados derivados de terópodos evolucionaron grandes tallas corporales, ocupando la cima del nicho de depredador durante todo el Jurasico y el Cretácico. Durante el Jurasico Medio prevalecieron clados de tetanuros basales mayormente endémicos, mientras que durante el Jurásico Superior-Cretácico Medio clados más derivados de terópodos tetanuros “intermedios” de afinidades cosmopolitas ocuparon el papel de gran depredador, incluyendo sinraptoridos, espinosauridos y carcharodontosauridos. Finalmente, durante los ultimos 20 millones de anos del Cretacico, coelurosaurios mas derivados con aspecto reminiscente a las aves alcanzaron grandes tallas corporales. Pirmordialmente entre estas formas se hallaban los tiranosauridos, una radiación septentrional (asiáticos y norteamericanos) de megadepredadores cuyo ascenso a la cumbre del nicho de gran depredador se retraso hasta el Campaniense y Maastrichtiense. Mientras Asia continua constituyendo el foco de una intensa actividad paleontológica, nuestros conocientos sobre la evolución de los grandes terópodos continuará refinándose con el estudio de futuros hallazgos

"Microscopic" approach to the Ricci dark energy

A derivation of the Ricci dark energy from quantum field theory of fluctuating "matter" fields in a classical gravitational background is presented. The coupling to the dark energy, the parameter 'a', is estimated in the framework of our formalism, and qualitatively it appears to be within observational expectations.Comment: 7 page