Searching for gravitational radiation from Scorpius X-1: Limits from the second LIGO science run
Searching for the fifth dimension using gravitational waves
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Mike Cruise
University of Birmingham
Searching for the fifth dimension using gravitational waves
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Gravitational Waves• The science cases for
AdLIGO, VIRGO, LISA, etc are very strong and first detections are expected in the milliHz to kilo Hz range.
• These astronomical sources are well identified, mostly observed already using other techniques and quite well understood theoretically
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GW’s at Very High Frequencies
• By contrast, the case for sources at frequencies above 1MHz is far more speculative and less developed.
• There are three generic sources at frequencies above 1 MHz– The early universe– EM-GW conversion in astrophysical
plasmas– Black Hole infall in 5-D gravity
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Brane Oscillations in 5D
• Seahra and Clarkson have calculated the GW emission in 5-D gravity when gravitational interactions take place between a black hole and an orbiting star
• There is the normal LF radiation from such a system, but there is also excitation of the brane separation itself
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lldp e
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MRkpcMxh 2/)5(
5.021 1.011
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This is a Source which exists!
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Brane Oscillations
• Speculative Physics but a clear motivation
• Strong signals but many parameters unknown
• For sources at the Galactic Centre, there might be enough knowledge of the stellar statistics to place limits on 5D theories, or even make a detection!!.
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Measuring GW’s:Laser Interferometry
Laser
Photodiode
Mass
Mass
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A GW interacts with a static Magnetic Field
• De Logi and Mickelson (1977)
• • • • Cross Section for g >
Graviton
Virtual Photon( Static Magnetic Field )
Photon
3
228
c
LGBSpin states of g, B and
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Higher Energy Density
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Current Optical Detector
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Current Plans
• The Birmingham Optical GW detector is operational now and observes the Galactic Centre with a ~15% time efficiency. Efforts are being made to raise this to about 60%
• Jodrell Bank and Birmingham are designing an interferometer working at 30GHz as well
• Future technology possibilities include internal magnetic fields in ferromagnets, etc to improve sensitivity
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Conclusion
• Gravitational Wave science at high frequencies may allow tests of 5D gravity models.
• Upper limits from the current prototypes should start appearing next year
• Turning the experimental results into science will require better understanding of brane-world parameters and the astrophysics of the Galactic Centre
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