Louisiana State University Physics & Astronomy

Experimental & Theoretical General Relativity

Diener - Giaime - Gonzalez - Hamilton - Johnson - Lehner - Pullin

The general relativity group includes collaborations with other faculty members of the department and with professors at other institutions. It has several postdoctoral fellows and graduate students. LSU has both theoretical and experimental activitiesin gravitational physics.

The experimental activities are centered on two complementary areass: a search for the first direct detection of gravitational radiation (or "gravity waves") and development of the instrumentation for much more sensitive searches. ALLEGRO has often been the world's most sensitive and reliable observing instrument during the last five years. Data are exchanged with the four comparable instruments around the world, operated by the INFN and, the University of Western Australia. To date, evidence sufficient to claim the discovery of a gravitational wave has not been seen.

All gravitational antennas convert the "tidal" (or differential) acceleration of the wave into mechanical motion or vibration, which then must be detected by a transducer. The expected signals are very small. The current antenna is sensitive to vibration amplitudes of about 10-18 meters, perhaps sufficient for detecting a gravitational collapse in our galaxy. In addition, the construction and commissioning of LIGO (Laser Interferometer Gravitational Wave Observatory) is taking place on LSU land near the campus. This is a 4 km Fabry-Perot Michelson interferometer operated by Caltech and MIT that, when it is operating, should be able to detect gravitational waves from a wide variety of sources located far outside our galaxy.

The development activities are oriented toward major improvements in the sensitivity of observing instruments, rather than proofs of principle. The first activity is further development of the technology used on ALLEGRO. This comprises the physics and engineering of higher mechanical quality factors, the reduction of residual AC resistance in superconductors, and the improvement of SQUID amplifiers.

As a part of the LIGO Science Collaboration, LSU scientists are working on improvements to LIGO that will be implemented in future upgrades. This involves research on fundamental noise sources and on techniques by which cryogenics can be used to decrease instrument noise.

The theoretical activities include the simulation of binary "compact objects" such as black holes, neutron stars and white dwarfs. The group has developed several large codes including the ability to run on parallel supercomputers and to include adaptive mesh refinement and multi-patch capabilities for the simulation of the Einstein equations of general relativity. Some of the codes allow coupling to fluids and magneto-hydrodynamics. The group also includes research in more foundational questions of gravity including mathematical issues and quantum issues including loop quantum gravity. More information can be found on the Theoretical General Relativity Group webpage.

Updated: Wed, 02-Apr-2008 9:25 AM