Kazuhiro Yamamoto Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut)

1. Gravitational wave and detectors Kazuhiro Yamamoto Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut) Institut fuer Gravitationsphysik, Leibniz Universitaet Hannover 6 May 2010 @Università degli Studi di Trento, Trento, Italy

2. 6 May 2010 (Afternoon) Gravitational wave and detectors 7 May 2010 (Morning) Fundamental noise of interferometric gravitational wave detectors

3. 0.Abstract I would like to explain … (1) What is the gravitational wave ? (2) Why do we want to detect gravitational wave directly ? (3) How can we detect gravitational wave ? (4) What kinds of detector are there ? Did they provide scientific results ? (5) What kinds of detector will there be ? Will they be able to detect gravitational wave ?

4. Contents 1. Gravitational wave 2. Aims of detection 3. Outlines of detectors 4. Recent results in observation 5. Summary

5. 1.Gravitational wave What is the gravitational wave ? 1915 A. Einstein : General theory of Relativity “Gravitation is curvature of space-time.” 1916 A. Einstein : Prediction of gravitational wave “Gravitational wave is ripple of space-time.” A. Einstein, S. B. Preuss. Akad. Wiss. (1916) 688. Wikipedia (A. Einstein, English)

6. 1.Gravitational wave Gravitational wave Speed is the same as that of light. Transverse wave and two polarizations http://spacefiles.blogspot.com

7. 1.Gravitational wave Interaction of gravitational wave is too weak ! Artificial generation is impossible ! Noexperiment which corresponds to Hertz experiment for electromagnetic wave Astronomical events Strain [(Change of length)/(Length)] : h ~ 10-21 (Hydrogen atom)/(Distance between Sun and Earth) No direct detection until now

8. 1. Gravitational wave Indirect detection of gravitational wave Binary pulsar (R.A. Hulse and J.H. Taylor, Astrophysical Journal 195 (1975) L51.) Generation of gravitational wave Energy emission Change of period of binary Observed change of period agrees with theoretical prediction by radiation formula of gravitational wave. J.H. Taylor et al., Nature 277 (1979) 437.

9. 1.Gravitational wave Recent result J.M. Weisberg and J.H. Taylor, ASP Conference Series, 328 (2005) 25 (arXiv:astro-ph/0407149). 9

10. 1.Gravitational wave Web site of Nobel foundation

11. 2.Aims of detection No direct detection until now What is the motivation ? Physics : Experimental tests for theory of gravitation Astronomy : New window for astronomical observation

12. 2.Aims of detection Physics : Experimental tests for theory of gravitation (1) Speed : Alternative theories of gravitation predict the difference of speed between gravitational wave and light. C.M. Will, “Theory and experiment in gravitational physics”(1993) Cambridge University Press.

13. 2.Aims of detection (2) Polarization : Alternative theories of gravitation predict the 6 kinds of polarizations (General relativity : 2).

14. 2.Aims of detection Astronomy : New window for observation Gravitational wave astronomy Gravitational wave sources (1) Burst source (2) Periodic source (3) Stochastic source

15. 2.Aims of detection • (1) Burst source : Supernova Mechanism of the core-collapse SNe still unclear Shock Revival mechanism(s) after the core bounce. GWs generated by a SNe should bring information from the inner massive part of the process and could constrains on the core-collapse mechanisms. M. Punturo, GWDAW Rome 2010

16. 2.Aims of detection (1) Burst source : Compact binary coalescence Neutron star, Black hole quasi-mode oscillation coalescence chirp signal -300Hz -1kHz K. Kuroda Fujihara seminar (2009) msec New standard candle for measurement of distance Equation of state at high density, formation black hole

17. 2.Aims of detection (2) Periodic source : Pulsar Rotating neutron star Asymmetry of shape Structure of interior M. Punturo, GWDAW Rome 2010

18. 2.Aims of detection (3) Stochastic source (Background) • Astronomical sources • Compact binary (b) Cosmological sources (Early universe) Cosmic Gravitational wave Background ? Quantum fluctuation in inflation Phase transition at early universe (Grand Unified Theory(cosmic string), Electroweak, QCD, …)

19. 3.Outlines of detectors There are a lot of kinds of detectors ! Resonant detector Interferometer (on Earth) Interferometer (Space) Doppler tracking Pulsar timing Polarization of cosmic microwave background and so on … Frequency range : 10-18 Hz – 108 Hz

20. 3.Outlines of detectors Resonant detector Gravitational wave excites resonant motion of elastic body. Weber bar (most popular one) “300 years of gravitation” (1987) Cambridge University Press Fig. 9.8 Diameter : several tens cm Length : a few meters Resonant frequency : about 1 kHz

21. 3.Outlines of detectors Joseph Weber (1919-2000) Pioneer of gravitational wave detection He is one of persons who proposed the concept of laser. Other persons (C.H. Townes, N.G. Basov, A.M. Prokhorov) won Nobel prize in Physics (1964). He started development of resonant detector. J. Weber, Physical Review 117 (1960) 306.

22. 3.Outlines of detectors Weber event J. Weber, Physical Review Letters 22 (1969) 1302. “Evidence for discovery of gravitational radiation” Coincidence between two detectors (Distance is 1000 km) Direction of sources : Center of our galaxy

23. 3.Outlines of detectors However, … Theorists pointed out that our galaxy disappears in short period if center of galaxy emits so large energy. No experimentalists could confirm Weber event even if they used detectors with better sensitivity ! We do not know what caused Weber event, but gravitational wave did not.

24. 3.Outlines of detectors First generation (room temperature) University of Maryland (U.S.A.) … Second generation (4 K) Explorer (Italy, CERN), Allegro (U.S.A.), Niobe (Australia), Crab (Japan) … Third generation (< 100 mK) Nautilus (Italy), Auriga (Italy), Mini-Grail (Netherlands), Mario Schenberg (Brazil) … This is not a perfect list !

25. 3.Outlines of detectors First generation (room temperature) University of Maryland (U.S.A.) … Second generation (4 K) Explorer (Italy, CERN), Allegro (U.S.A.), Niobe (Australia), Crab (Japan) … Third generation (< 100 mK) Nautilus (Italy), Auriga (Italy), Mini-Grail (Netherlands), Mario Schenberg (Brazil) …

26. Exploler G. Pizzella, ET first general meeting (2008)

27. NAUTILUS INFN - LNF G. Pizzella, ET first general meeting (2008)

28. 3.Outlines of detectors AURIGA Padova G. Pizzella, ET first general meeting (2008)

29. 3.Outlines of detectors About 3 kHz Mini-Grail Mario Schenberg O.D. Aguiar et al., Classical and Quantum Gravity 25 (2008) 114042. http://www.minigrail.nl/

30. 3.Outlines of detectors Old but original resonators in Japan (Not bar and sphere) One of examples : Torsion detector (60 Hz) “Gravitational wave detection” Kyoto University Press (1998) Fig. 5-6. (Japanese) Best upper limit of continuous gravitational wave from Crab pulsar h<2*10-22 (Until 2008) T. Suzuki, “Gravitational Wave Experiments” World Scientific p115 (1995). S. Kimura et al., Physics Letters A 81 (1981) 302.

31. 3.Outlines of detectors Interferometer (on Earth) Gravitational wave changes length difference of two arms. Frequency : 10 Hz – 10 kHz

32. 3.Outlines of detectors Brief early history of interferometer “300 years of gravitation”(1987) Cambridge University Press Idea or suggestion F.A.E. Pirani (1956), Gertsenshtein and Pustovoit (1962), J. Weber (mid-1960’s) Detailed design and feasibility study R. Weiss (1972) First interferometric detector G.E. Moss, L.R. Miller, R.L. Forward, Applied Optics 10 (1971) 2495.

33. 3.Outlines of detectors All current interferometers have Fabry-Perot cavities.

34. 3.Outlines of detectors First generation (Current) LIGO (U.S.A.), VIRGO (Italy and France), GEO (Germany and U.K.), TAMA (Japan), CLIO (Japan) Second generation (Future) Advanced LIGO, Advanced VIRGO, AIGO(Australia), LCGT (Japan) Third generation (Future) Einstein Telescope (Europe)

35. 3.Outlines of detectors Sensitivity of interferometer 1st generation (LIGO,VIRGO) 10 times 2nd generation 10 times ? 3rd generation

36. 3.Outlines of detectors LIGO (U.S.A.) 4 km, Hanford and Livingston (3000 km distance) (U.S.A.) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

37. 3.Outlines of detectors VIRGO (Italy and France) 3 km, Pisa (Italy) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

38. 3.Outlines of detectors GEO (Germany and U.K.) 600 m, Hannover (Germany) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

39. 3.Outlines of detectors TAMA (Japan) 300 m, Tokyo (Japan) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

40. 3.Outlines of detectors CLIO (Japan) 100 m, Kamioka (Japan) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

41. 3.Outlines of detectors What will happen in future ? Before second generation … GEO-HF (High Frequency) Upgrade of GEO600 Observation : 2011-2015 H. Lueck et al., Journal of Physics: Conference Series Coming soon (arXiv:1004.0339). Injection of squeezed light (smaller quantum vacuum fluctuation of light) Henning Vahlbruch et al., Classical and Quantum Gravity 27 (2010) 084027. (GWIC thesis prize in 2008)

42. 3.Outlines of detectors Second generation Observation : 2015 ? – We can expect first detection ! Advanced LIGO, Advanced VIRGO Upgrade of LIGO and VIRGO AIGO (Australia) Similar to Advanced LIGO LCGT (Japan) Cryogenic technique Underground site (small seismic motion)

43. 3.Outlines of detectors AIGO (Australia) 8 km, Perth (Australia) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

44. Location of LCGT 3 km, Kamioka (Japan) LCGT is planed to be built underground at Kamioka, where the prototype CLIO detector is placed. By K. Kuroda (2009 May Fujihara seminar)

45. 3.Outlines of detectors CLIO (Japan) Prototype for LCGT (cryogenic technique, same underground site) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001. 45

46. 3.Outlines of detectors Third generation Observation : 2025 ? – Einstein Telescope (Europe) 30 km vacuum tube in total Cryogenic technique Underground site (small seismic motion)

47. World wide network for GW astronomy GEO600 GEO HF LIGO(I) Hanford LCGT Adv. LIGO (under construction since 2008） TAMA/CLIO LCGT, Budget request Virgo Adv. Virgo (design) LIGO(I) Livingston AIGO (budget request) ET (planed) A network of detectors is indispensable to position the source. By K. Kuroda (2009 May Fujihara seminar)

48. 3.Outlines of detectors M. Punturo et al., Classical and Quantum Gravity 27 (2010) 084007.

49. 4.Recent results in observation Future interferometers can detect gravitational wave. Current interferometers have never detected ! However, current interferometers have already provided scientific results in astronomy and cosmology. • Gamma ray burst • (2) Crab pulsar • (3) Stochastic background

50. 4.Recent results in observation (1) Gamma ray burst Gamma ray flashes with huge energy 1963 : Vela satellite (U.S.A.) found gamma ray burst. R. Klebesadel et al., Astrophysical Journal 182 (1973) L85. Gamma ray bursts appear suddenly and disappear soon. Nobody knows what they are and how much distancesfrom Earth are.