1. Detection of Gravitational Waves with Interferometers

2. Gravitational waves
Transverse distortions of the space-time itself  ripples of space-time curvature
Propagate at the speed of light
Push on freely floating objects (e.g. the ‘free’ mirrors of an interferometer)  stretch and squeeze the space transverse to direction of propagation
Emitted by astrophysical sources

3. Measurement and the real world
How to measure the gravitational-wave?
Passing GW displaces the mirrors of an interferometer
Measure those displacements by measuring the phase shifts of the light
What makes it hard?
GW amplitude is small – h ~ from the inspiral of NS binaries in the Virgo cluster
External forces also push the mirrors around
Laser light has fluctuations in its phase and amplitude

4. LIGO: Laser Interferometer Gravitational-wave Observatory3 k m ( 1 s )
MIT WA
4 km
Caltech LA
4 km

5. Global network of detectors
GEO
VIRGO
LIGO
TAMA
AIGO
LIGO
Detection confidence
Source polarization
Sky location
LISA

7. Initial LIGO’s Science Goals
Interferometer commissioning
Intersperse commissioning and data taking consistent with obtaining one year of integrated data at h = by end of 2006
Science runs and astrophysical searches
Science data collection and intense data mining interleaved with commissioning
S1 Aug 2002 – Sep duration: 2 weeks
S2 Feb 2003 – Apr duration: 8 weeks
S3 Oct 2003 – Jan duration: 10 weeks
S4 Feb 2005 – Mar duration: 4 weeks
S5 Nov 2005 – duration: 1 yr integrated
Advanced LIGO

8. Science runs and sensitivity
1st Science Run
Sept 02
(17 days) S2
2nd Science Run
Feb – Apr 03
(59 days) S3
3rd Science Run
Nov 03 – Jan 04
(70 days)
Strain (sqrt[Hz]-1)
LIGO Target Sensitivity S5
5th Science Run
Nov 05 onward
(1 year integrated) S4
4th Science Run
Feb – Mar 05
(30 days)
Frequency (Hz)

9. Astrophysical sources of GWs
Periodic sources
Pulsars
Low mass Xray binaries
Coalescing compact binaries
NS-NS, NS-BH, BH-BH
Burst events
Supernovae with asymmetric collapse
Gamma-ray bursts
GWs
neutrinos
photons
now
Stochastic background
Primordial Big Bang (t = sec)
Continuum of sources
The Unexpected

10. Advanced LIGO Factor 10 better amplitude sensitivity
(Reach)3 = rate
Factor 4 lower frequency bound
Hope for NSF funding in FY08
Infrastructure of initial LIGO but replace many detector components with new designs
Expect to be observing 1000x more galaxies by 2013
NS Binaries
Initial LIGO: ~15 Mpc
Adv LIGO: ~300 Mpc
BH Binaries
Initial LIGO: 10 Mo, 100 Mpc
Adv LIGO : 50 Mo, z=2
Stochastic background
Initial LIGO: ~3e-6
Adv LIGO ~3e-9

11. The LIGO-MIT group Who we are...
Faculty and senior research staff
Rai Weiss (emeritus), Erik Katsavounidis, Nergis Mavalvala, David Shoemaker, Peter Fritschel
Post-docs and junior research staff
Cadonati, Harry, Innerhofer, Mikhailov, Ottaway, Sarin, Zanolin
Graduate students
Ballmer, Betzwieser, Blackburn, Corbitt, Fotopoulos, Goda, Markowitz, Ruet, Shapiro, Wipf
Engineering staff
Undergraduates

12. What we do... Build interferometers
Initial LIGO is up and running
Enhancements expected in the next 3 years
Analyze the data to search for known and unknown astrophysical sources
Transient (or burst) source searches (Katsavounidis)
Stochastic background search (Fritschel)
Build better interferometers
Advanced LIGO likely to receive construction funds starting 2008
Quantum optics and quantum measurement group (Nergis)
Dream of detectors in space

13. Ultimate success… New Instruments, New Field, the Unexpected…