Einstein’s Unfinished Symphony: Gravitational Wave Detection

1. Einstein’s Unfinished Symphony: Gravitational Wave Detection Ho Jung PaikUniversity of Maryland and Seoul National UniversityKorean Physical Society MeetingJeon-Ju, Korea, October 21, 2005

2. Gravitational Wave Detection Gravitational wave is transverse and has spin 2. Joseph Weber (c1960) KPS - Paik

3. Resonant-Mass Detector Condition to detect a GW pulse with strength h: : energy coupling Optimal strategy: KPS - Paik

4. Resonant Transducer To get large , a resonant mass is attached to the antenna (Paik, 1972). The displacement of the secondary oscillator modulates a dc electric or magnetic field, or the frequency of a s/c cavity. Additional resonant masses can be added to increase S further. xM xm KPS - Paik

5. S/C Inductive Transducer KPS - Paik

6. Sensitivity of Resonant Detectors Noise in the detector Extrinsic: Seismic noise  mechanical filter Intrinsic: Thermal noise  cool detector Amplifier noise  SQUID amplifier amplifier transducer KPS - Paik

7. ALLEGRO 4-K antenna at LSU with a superconducting inductive transducer KPS - Paik

8. AURIGA 100-mK antenna in Italy with a capactive transducer coupled to a dc SQUID Best result obtained: h < 5x10-21 Hz-1/2 within ~100 Hz band KPS - Paik

9. Resonant Bar Detectors Allegro USA Niobe Australia Auriga, Italy Nautilus, italy Explorer Switzerland KPS - Paik

10. Network of Resonant Bars Allegro Auriga Explorer Nautilus Niobe IGEC Network KPS - Paik

11. International Gravitational Event Collaboration (IGEC) • ALLEGRO, AURIGA, EXPLORER, NAUTILUS, & NIOBE 1997-2000. • The search for bursts at resonance frequency ~ 900 Hz. • Candidate events at SNR > 3-5 (background ~ 100/day). • Data exchanged: peak amplitude, time of event and uncertainties. • Threshold equivalent to ~0.1 M⊙ converted into a gravity wave millisecond burst at a distance of 10 kpc. • The accidental coincidence rate over 1 s interval (i.e., bandwidth of 1 Hz) was ~ few/week two-fold and ~few/century three-fold. • No evidence for gravity wave bursts was found. KPS - Paik

12. IGEC Coincidence Search Upper Limit on the Rateof gravitational waves bursts from the GALACTIC CENTER Final results [P. Astone, et al. Phys. Rev. D68 (2003) 022001] rate [y –1] The area above the blue curve is excluded with a coverage > 90% search threshold h h~ 2 10-18 DE ~ 0.02 M⊙ converted @ 10 kpc KPS - 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 Antenna KPS - Paik

14. Resonant Spheres • Much larger cross-section than a bar of the same resonance frequency (up to 70 x) • Omni-directional: Allows the determination of direction and polarization • Hollow spheres could allow a choice of cross-sections and frequencies MiniGrail The Netherlands Schenberg Brazil The future?? KPS - Paik

15. As a wave passes, the arm lengths change in different ways…. Interferometer Concept Interferometer Detectors • Laser used to measure relative lengths of two orthogonal arms • Arms in LIGO are 4 km • Measure difference in length to one part in 1021 or 10-18 meters …causing the interference pattern to change at the photodiode Suspended Masses KPS - Paik

16. Interferometer Hardware Fused silica mirror 6-W Nd:YAG laser KPS - Paik

17. 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. Myriad details of the lasers, electronics, etc., can make problems above these levels Limiting Noise Sources KPS - Paik

18. Evolution of LIGO Sensitivity KPS - Paik

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

20. Network of Interferometers LIGO Virgo GEO TAMA AIGO decompose the polarization of gravitational waves detection confidence locate the sources KPS - 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 (J1939+2134) 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. KPS - Paik

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

23. Advanced LIGO Multiple Suspensions Sapphire Optics Active Seismic Higher Power Laser KPS - Paik

24. Advanced LIGO 2008 + • Enhanced Systems • laser • suspension • seismic isolation • test mass Rate Improvement ~ 104 narrow band optical configuration KPS - Paik

25. Gravitational Waves in Space LISA 2012 + Three spacecraft form an equilateral triangle with sides 5 million km in length. KPS - Paik

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

27. LISA Spacecraft Y-shaped payload has two identical optical assemblies with transmit/receive telescopes and optical benches. The inertial sensor consists of a free-falling proof mass inside a reference housing is fixed to the spacecraft. KPS - Paik

28. LISA and LIGO KPS - Paik

29. Conclusions • Sensitivity toward gravitational wave detection is improving on many fronts. • Improved upper 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 !! KPS - Paik