Paik-1 Search for Gravitational Waves Ho Jung Paik University of Maryland and Seoul National University January 12, 2006 Seoul, Korea KIAS-SNU Physics Winter Camp

Paik-2 Gravitational Waves Field equation in General Relativity:  A wave equation, in the weak-field limit. Transverse, spin 1 EM wave: Gravitational wave: Transverse, spin 2

Paik-3 Gravitational Wave Detection Joseph Weber (c1960) A gravitational wave will deposit energy into an elastic solid. (Weber, 1959)

Paik-4 Resonant-Mass Detector 1 Antenna  Transducer  Amplifier Transducer is characterized by an impedance matrix. Electromechanical energy coupling: f()f()u()u()I()I()V()V()

Paik-5 Resonant-Mass Detector 2 Condition to detect a GW pulse with strength h: Optimal strategy: Signal Antenna noiseAmplifier noise Thermal Wideband Backaction

Paik-6 Resonant Transducer To get large , a resonant mass is attached to the antenna (Paik, 1972 )  Displacement gain: (M/m) 1/2  10 2  Energy transfer time:   (  /  a ) (M/m) 1/2 An additional resonant mass with  = (Mm) 1/2 can be added to increase  S further.  Energy transfer time:   (  /  a ) (M/m) 1/4

Paik-7 S/C Inductive Transducer

Paik-8 ALLEGRO 4-K antenna at LSU with a superconducting inductive transducer

Paik-9 AURIGA Best result obtained: h < 5 x Hz -1/2 within ~100 Hz band 100-mK antenna in Italy with a capactive transducer coupled to a dc SQUID

Paik-10 Explorer Switzerland Allegro USANiobe Australia Nautilus, italy Auriga, Italy Resonant Bar Detectors

Paik-11 Network of Resonant Bars Allegro Explorer Auriga Nautilus Niobe IGEC Network

Paik-12 Rate (y –1 ) Search threshold h h ~ 2  ~ 0.02 M ⊙ 10 kpc Upper limit on the rate of gravitational waves bursts from the Galactic Center ( ) The area above the blue curve is excluded with a coverage > 90% P. Astone, et al. PRD 68 (2003) IGEC Coincidence Search No evidence for gravity wave bursts was found.

Paik-13 Spherical Antenna Sphere is omni-directional. By detecting its 5 quadrupole modes, the source direction ( ,  ) and wave polarization (h+, h  ) can be determined. (Wagoner & Paik, 1976) 6 radial transducers on truncated icosahedral configuration maintains “spherical” symmetry. (Johnson & Merkowitz, 1993)  TIGA (Truncated Icosahedral Gravitational Antenna)

Paik-14 Resonant Spheres Much larger cross-section than a bar of the same resonance frequency (up to 70 x) MiniGrail The Netherlands Schenberg Brazil

Paik-15 Interferometer Concept  Laser used to measure relative lengths of two orthogonal arms  Arm lengths in LIGO are 4 km  Measure difference in length to m

Paik-16 LIGO Hardware 6-W Nd:YAG laser Fused silica mirror

Paik-17 Limiting Noise Sources  Seismic noise limits at low frequencies.  Atomic vibrations (thermal noise) inside the components limit at mid frequencies.  Quantum nature of light (shot noise) limits at high frequencies.

Paik-18 Evolution of LIGO Sensitivity

Paik-19 Interferometer Detectors LIGO Louisiana 4000m TAMA Japan 300m Virgo Italy 3000m GEO Germany 600m LIGO Washington 2000m & 4000m

Paik-20 Network of Interferometers LIGO detection confidence GEO Virgo TAMA AIGO? locate the sources decompose the polarization of gravitational waves

Paik-21 LIGO Science Has Begun S1 run: 17 days (Aug - Sep 2002) Primarily methods papers Four astrophysical searches published (Phys. Rev. D 69, 2004): Inspiraling neutron stars, bursts, known pulsar (J ) with GEO, stochastic background S2 run: 59 days (Feb - April 2003) Analyses are mostly complete. S3 run: 70 days (Oct 2003 – Jan 2004) Analysis is in full swing.

Paik-22 Promising Source: Compact Binaries

Paik-23 Matched Filtering “chirps ” NS–NS: waveforms are well described BH–BH: need better waveforms Search: matched templates

Paik-24 Advanced LIGO Active Seismic Multiple Suspensions Improved Optics Higher Power Laser

Paik-25 Sensitivity Improvement Rate Improvement ~ 10 4 narrow band optical configuration

Paik-26 Gravitational Waves in Space Three spacecraft form an equilateral triangle with armlength of 5 million km LISA

Paik-27 LISA Accelerometer The position of a reference mass is sensed by a capacitor bridge and used for drag-free control.

Paik-28 Y-shaped payload has two identical optical assemblies with transmit/receive telescopes. The inertial sensor consists of a free-falling proof mass inside a reference housing. LISA Spacecraft

Paik-29 Sources for LISA

Paik-30 LISA and LIGO

Paik-31 Status of Interferometers  Sensitivity toward gravitational wave detection is improving on many fronts.  Improved limits are being set for all major sources -- binary inspirals, periodic sources, burst sources, and stochastic background.  Data exchange and joint data analysis between detector groups is improving ability to make detections.  Need specific waveforms to improve search sensitivities!  Hopefully, detections will be made soon !!