This series consists of talks in areas where gravity is the main driver behind interesting or peculiar phenomena, from astrophysics to gravity in higher dimensions.
I discuss a model for particle acceleration in the current sheet separating the open and closed field line regions, and crossing the
neutral line region, of a pulsar's magnetosphere, which has substantial kinship to the phenomena observed in planetary magnetospheres within the solar system. Possible applications to gamma ray emission from pulsars are also described.
A remarkable result from heavy ion collisions at the Relativistic Heavy Ion Collider is that shortly after a collision, the medium produced behaves as a nearly ideal liquid. The system is very dynamic and evolves from a state of two colliding nuclei to a liquid in a time roughly equivalent to the time it takes light to cross a proton. Understanding the mechanisms behind the rapid approach to a liquid state is a challenging task.
Over the last decade there has been strong interest in the theory and phenomenology of particle propagation in quantum spacetime. The main results concern possible Planck-scale modifications of the "dispersion" relation between energy and momentum of a particle. I review results establishing that these modifications can be tested using observations of gamma rays from sources at cosmological distances. And I report recent progress in the understanding of the implications of spacetime expansion for such studies.
Coincident detections of electromagnetic and gravitational wave signatures from the merger of supermassive binary black holes are the next observational grand challenge. Such detections will provide a wealth of opportunities to study gravitational physics, accretion physics, and cosmology. Understanding the conditions under which coincidences of electromagnetic and gravitational wave signatures arise during supermassive black hole mergers is therefore of paramount importance, requiring multi-scale/physics computational modeling.
For the past century, there has been much discussion and debate about the equations of motion satisfied by a classical point charge when the effects of its own electromagnetic field are taken into account. Derivations by Abraham (1903), Lorentz (1904), Dirac (1938) and others suggest that the "self-force" (or "radiation reaction force") on a point charge is given in the non-relativistic limit by a term proportional to the time derivative of the acceleration of the charge.
Gas accretion onto black holes is thought to power some of the most energetic astrophysical phenomena observed. Black hole accretion disks are efficient engines for converting binding energy into light, and for launching relativistic unbound flows (jets) such as in gamma ray bursts, microquasars and radio-loud active galactic nuclei (AGN). Some systems individually exhibit a wide variety of spectral and bolometric states while others remain remarkably predictable. As
Galaxy mergers, which are a natural consequence of hierarchical assembly of galaxies, are expected to produce binary black holes, which subsequently merge. The detection and analysis of gravitational waves from these sources is the major aim of the next generation gravitational wave detector: LISA, the Laser Interferometric Space Antenna.
Binary neutron stars are among the most important sources of gravitational waves which are expected to be detected by the current or next generation of gravitational wave detectors, such as LIGO and Virgo, and they are also thought to be at the origin of very important astrophysical phenomena, such as short gamma-ray bursts. In order to describe the dynamics of these events one needs to solve the full set of general relativistic magnetohydrodynamics equations through the use of parallel numerical codes.