LIGO-G050002-00-Z
Einstein@home: how to find gravity waves with your home PC
Michael LandryLIGO Hanford ObservatoryCalifornia Institute of Technology
Say Hello to Einstein@homeLHO June 8, 2005
Photo credit: NASA/CXC/SAO
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Detecting a signal
• Greg has talked about sources• Now let’s talk about detection• If our detector was not moving with
respect to a star, gravity waves would sound like a single tone
• Gravity waves from dense spinning stars are Doppler shifted by the motions of the Earth relative to the star (FM)
• Gravity waves are also amplitude modulated because interferometer sensitivity varies with direction (AM)
Waves get Doppler shifted
from relative motion
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Simulation:Gravitational Waves Seen & Heard
Play Me
(AM & FM modulation greatly exaggerated)
Power vs sky position
Power vs frequency
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Detecting a signal
• Steps in detection:» Guess at what the signal might look like» Compare your guess to your data from
your interferometer» This is called matched filtering» If you don’t find a signal, keeping
guessing and comparing
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: Data from detector
: “Guess” at signal
Match!!
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Why distributed computing?
• e.g. searching 1 year of data, you have 3 billion frequencies in a 1000Hz band
• For each frequency we need to search 100 million million independent sky positions
• pulsars spin down, so you have to consider approximately one billion times more “guesses” at the signal
• Number of templates for each frequency: ~100,000,000,000,000,000,000,000
• Clearly we rapidly become limited in the analysis we can do by the speed of our computer!
Einstein@home!!! a.k.a. Distributed computing
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Einstein@home
• Installation• Screensaver• Web pages• Getting help
APS webpagehttp://www.physics2005.org/events/einsteinathome/index.html
Einstein@home webpagehttp://einstein.phys.uwm.edu/
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Summary
• Run Einstein@home on your home PC! Tell your friends! Tell your enemies! You may be the first person in history to detect gravity waves on your computer!
• You should have received a pamphlet with instructions on how to load the screen saver
• Included with the pamphlet is a survey; please fill this out and drop it in the box on the way out the door. Take a cookie for your trouble
• Need help? [email protected]• After the talks: I’ll demonstrate the installation if
anyone is interested