Photo credit: NASA/CXC/SAO

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

Landry - Einstein@home, 8 Jan 2005 2LIGO-G050002-00-Z

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


Simulation:Gravitational Waves Seen & Heard

Play Me

(AM & FM modulation greatly exaggerated)

Power vs sky position

Power vs frequency


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


: Data from detector



: “Guess” at signal




Match!!


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


Einstein@home

• Installation• Screensaver• Web pages• Getting help

APS webpagehttp://www.physics2005.org/events/einsteinathome/index.html

Einstein@home webpagehttp://einstein.phys.uwm.edu/


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

Photo credit: NASA/CXC/SAO

Documents

Transcript of Photo credit: NASA/CXC/SAO