University of Minnesota
School of Physics & Astronomy


Gravitational waves

Vuk Mandic
Vuk Mandic
Alex Schumann

Professor Vuk Mandic is an observational cosmologist involved in the search for gravitational waves with LIGO (Laser Interferometer Gravitational-wave Observatory.) Gravitational Waves were predicted by Einstein’s Theory of General Relativity, but have yet to be observed in the natural world.

They are expected to be produced in some of the most violent events in the Universe, such as mergers of black holes or neutron stars. Moreover, gravitational waves are expected to be created a fraction of a second after the Big Bang, so they could provide a glimpse of a much younger Universe than what is possible with other observational approaches.

LIGO has build three laser interferometers, designed to search for gravitational waves. With suspended interferometer mirrors separated by 4 km, these interferometers are sensitive to distance fluctuations at the level of one ten-thousandth of the proton size, sufficient to detect some of the strongest sources of gravitational waves. Two such interferometers are sharing the same facility at Hanford, WA, and the third is located at Livingston Parish, LA.

Mandic, his students, and post-docs focus on the searches for the stochastic gravitational-wave background, one of four signal types being sought by LIGO (the other three being bursts, inspiraling coalescences, and periodic sources). To minimize the effect of local disturbances at the LIGO observatories such as seismic noise, wind, traffic etc, these searches are performed by cross-correlating the data streams from different interferometers.

Last January LIGO announced new upper limits on the amplitude of the stochastic gravitational-wave background. This result was based on one year of data LIGO acquired operating at its designed sensitivity and it is the most sensitive limit to date. This result is beginning to constrain some of the theoretical models, such as models of cosmic (super)strings. Future LIGO runs, with improved sensitivities, will continue to probe such models, helping theorists hone their theories to the realities of nature.

Mandic is also involved in development of the germanium detectors for the Cryogenic Dark Matter Search (CDMS) experiment, which is taking place in the Soudan Underground Laboratory. Mandic’s group is focusing on increasing the size of CDMS detectors, with the goal of simplifying the design of a ton-scale germanium-based dark matter search experiment. Such an experiment is expected to probe some of the most interesting theoretical models of dark matter. Mandic’s group is preparing a facility designed to test and characterize these germanium detectors.

More information at http://