Presentation on Gravitational Waves

Presentation on Gravitational Waves. Boy Group 623 604 630 613 635.

Gravitational-waves: Sources and detection Ravi kumar Kopparapu Center for Gravitational-Wave Physics (CGWP).

Gravity Einstein's General theory of relativity : Gravity is a manifestation of curvature of 4- dimensional (3 space + 1 time) space-time produced by matter (rnetric equation ? guv ) If the curvature is weak, it produces the familiar Newtonian gravity: F = G MI M2/r2.

Gravitational-waves VVhen the curvature varies rapidly due to Inotion of the object(s), curvature ripples are produced. These ripples of the space—tirne are Gravitational—veraves. Gravitational-Myraves propagate at the speed of light. Anin-ration by VVilliar-n Folkner, LISA project, JPL.

Electromagnetic (versus) Gravitational- waves ENI svaves are produced by accelerated charges, svhereas GVVs are produced by accelerated "rnasses". ENT propogate through space-tirne, GVVs are oscillations of space-tinie itself. Typical frequencies of ENI svaves range fronl (107 Hz Hz) svhereas G VV frequencies range fronl (10-9 Hz Hz). They are rnore like sound vvaves. — 1020 — 104.

Gravitational-waves GYVs stretch and cornpress the space-tirne in tvvo directions (polarizations): '+' and 'x'. h x phase O 2 2 h + & hx are tirne-varying and their arnplitude depend on the source that is ernitting GVVs..

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ources of GVMs Inspiral sources: Binary black holes, Binary Neutron stars (pulsars), Binary vvrhite-dwarfs or cornbination of these. As tvvo stars orbit around each other, they steadily lose energy and angular Inornenturn in the forni of GVVs. This Inakes the orbital separation to shrink slowly and they Inerge after sorne tirne (this tirne depends on their Inasses and orbital separation that observe).

Inspiraling binary stars.

Sources of GMsJs Exploding stars: Core collapse Supernovae Pulsars (rotating Neutron stars) Stochastic sources: Jurnble of signals fronm lot of sources.

ow do we know GVX/s exist ? Indirect proof. Hulse—Taylor binary pulsar (Nobel prize 1993) Steady decrease in orbital separation due to loss of energy through GVVs. —10 —20 General Relativity preciction E —25 — 30 — 40 1 975 1 980 1 985 1990 1995 2000 2005 Year.

etection of Gravitational-waves Ground based detectors: LIGO (U.S.A), VIRGO (Italy), GEO (Germany), TAMA (Japan), AURIGA (Australia) (Proposed) Space-based detectors: LISA (NASA-ESA).

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aser Interferometer vitaiona Observatory wave • LIGO urage test mass test mass laser æst mass light storage ann test mass tvarn Length of each arni, L 4 kni, frequency range , f = 10 Hz — 104 Hz AL — 10 18 rneters, size of proton 10-15 Ineters.

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Space-based GVV detection LISA (Laser Interferorneter Space Antenna).

Sources for LISA Double VVhite Dvvrarfs VVhite—dvvarf black hole Superrnassive and Interrnediate Inass black holes c, -22 o_wt Gravitational wave frequency (Hz).

What's the big deal ? GYVs bring info about objects that can not be seen with EM observations and vice-versa. This is a radically different field than ENI observations. Measuring a length srnaller than proton size is no longer a science fiction !! Observations have already been taken with the first version of LIGO (and VIRGO, GEO). We talked about signals and sources that we *know* about. Any new field has it's own surprises (radio, ganuna-ray). ethere are known knowns there are known unknowns, But there are also unknown unknowns Don Rurnsfeld.

The future Enhanced LIGO — 2010, Advanced LIGO — 2013 , Can see black hole binaries upto 4 Gpc (12 billion light years, z — 1) Advanced LIGO can detect hundreds of Inerger events in one year of observations because it can observe to larger distances !! Join us....ifyou are interested....

What are Gravitaitonal-waves ? Einstein's General theory of relativity : Gravity —+Curvature of 4-dirnensional (3 space + 1 tirne) space—tirne fabric produced by Inatter Gravitational-veaves —+Ripp1es on space—tirne produced by accelerated Inatter.

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