2 January 2008 : LIGO project sheds light on cosmic event with help from UWM [ More ]
12 November 2007 : Closing in on the origin of cosmic rays. [ More ]
09 October 2007 : Computer System Administrator for UNIX/Linux systems [ More ]
07 September 2007 : Postdoctoral positions with emphasis on LIGO software infrastructure [ More ]
14 August 2007 : Post-doctoral research position for the Einstein@Home project at UWM [ More ]
When Einstein published the special theory of relativity a century ago, it signaled the start of his decade long quest to develop a theory of gravitation that was consistent with his newly developed insights into space and time. It is now 90 years since Einstein first wrote the field equations of general relativity and revolutionized our understanding of gravitation. General relativity had immediate success with its ability to predict the advance of the perihelion of Mercury and its prediction of the bending of light (which was measured during the 1921 solar eclipse). Indeed the theory has passed every experimental test to date and has provided both dramatic predictions and explanations of physical phenomena in the Universe.
Counted among the most dramatic predictions of general relativity are black holes and gravitational waves. Both are manifestations of pure gravity which were only understood theoretically using general relativity. Scientists are now poised to probe general relativity, black holes and the early universe using gravitational waves as an astronomical tool. The Laser Interferometer Gravitational-Wave Observatory (LIGO), an ambitious NSF-funded project to detect gravitational waves from astrophysical sources such as coalescing neutron stars and black holes, spinning neutron stars, and supernovae, forms part of a worldwide network of gravitational-wave detectors which includes the British-German GEO detector, the French-Italian VIRGO detector and the Japanese TAMA detector.
The LIGO Scientific Collaboration (LSC), comprised of approximately 450 scientists from 40 institutions around the globe, is the entity within LIGO which carries out LIGO's scientific research program. The LSC includes members of the GEO Collaboration, which operates a 600 m interferometer near Hannover, Germany. Scientific analysis of data from the LIGO and GEO instruments is carried out in common. The LIGO detectors are now nearing design sensitivity, however. This makes the direct observation of gravitational waves plausible during the next science run (S5) which began in November 2005. LIGO has achieved a critical point where the astronomy community now eagerly awaits the first detection and the beginning of the new field of gravitational-wave astronomy.
In 2004, the National Science Board reaffirmed its long-term commitment to gravitational wave astrophysics by approving the Advanced LIGO upgrade to the interferometers. It is expected that by 2012 we will improve LIGO's sensitivity by at least an order of magnitude, increasing by three orders of magnitude the observable volume of the Universe. This should bring LIGO into an era of routine astronomical observations. Recent detections of several short, hard gamma-ray bursts (GRB) by HETE and Swift provide compelling evidence that binary neutron star (or neutron star/black hole) systems are the progenitors of these powerful explosions. They are also a tantalizing reminder of the potential scientific pay-off of combined electromagnetic and gravitational observing campaigns. As LIGO enters an era of almost continuous science running, it becomes urgent to process and analyze the data at the rate they are acquired. This will eventually allow transient gravitational-wave events to be quickly followed up with electromagnetic observations.
The inspiral and merger of a compact binary system generates gravitational waves which sweep upward in frequency and amplitude through the sensitive band of the Earth-based detectors. The detection of gravitational waves from these astrophysical sources will provide a great deal of information about strong field gravity, dense matter, and the populations of neutron stars and black holes in the Universe. Patrick Brady co-chairs the inspiral analysis group of the LIGO Scientific Collaboration. This working group's goal is to identify gravitational-wave signals from compact binary sources in the detector data, and estimate the waveform parameters. To date, no gravitational waves have been identified from these sources, so the scientific product of the group is to place limits on the coalescence rate of binaries in the Universe. When wave are detected, it will be possible to infer information about the binary populations, and possibly probe the disruption of neutron stars, test alternative theories of gravity, and bound the mass of the graviton. These are just some of the ideas for gravitational-wave astronomy and physics with these sources.
Maria Alessandra Papa co-chairs the pulsar group of the LIGO Scientific Collaboration. This working group's goal is to identify gravitational-wave signals which last for long times relative to the observing time. The archtypical gravitational-wave source is a rapidly rotating neutron star. These objects are already observed using radio telescopes, but the gravitational waves carry a host of new information about the structure of the neutron stars. Moreover, not all rapidly rotating neutron stars will be pulsars. This means that gravitational waves provides an new way to find these objects in our Galaxy. Since the search methods are not tied particularly to pulsars, there may be unexpected sources which continuously emit gravitational waves.
Commodity cluster computing has become a standard method of achieving high performance at low cost. Bruce Allen built the first Beowulf cluster at UWM in 1998 with the help of (then postdoc) Warren Anderson. In 2001, the group added a 300-node state of the art cluster (Medusa) designed for fast-turnaround and prototyping data analysis. This cluster served as a pathfinder in the LSC deploying Condor and distributing data across the cluster using cheap commodity hard disks to achieve 24 Tbytes of storage. In 2004, the group was awarded a National Science Foundation award to build a new cluster called Nemo, to be deployed in 2006. LAL Home Page GRASP Distribution Data Analysis Software Working Group (DASWG) LSC DataGrid