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

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

3. 0.Abstract 3 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 4

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.” 5 Wikipedia (A. Einstein, English) A. Einstein, S. B. Preuss. Akad. Wiss. (1916) 688.

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

7. 7 Interaction of gravitational wave is too weak ! Artificial generation is impossible ! No experiment 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. 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. 9 1.Gravitational wave Recent result J.M. Weisberg and J.H. Taylor, ASP Conference Series, 328 (2005) 25 (arXiv:astro-ph/0407149).

10. 10 1.Gravitational wave Web site of Nobel foundation

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

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

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

14. 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. 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. 16 2.Aims of detection (1) Burst source : Compact binary coalescence Neutron star, Black hole msec chirp signal coalescence quasi-mode oscillation -300Hz-1kHz K. Kuroda Fujihara seminar (2009) New standard candle for measurement of distance Equation of state at high density, formation black hole

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

18. 18 2.Aims of detection (3) Stochastic source (Background) (a)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. 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 – 10 8 Hz

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

21. 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. 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. 23 3.Outlines of detectors However, … 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. Theorists pointed out that our galaxy disappears in short period if center of galaxy emits so large energy.

24. 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. 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. 26 Exploler G. Pizzella, ET first general meeting (2008)

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

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

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

30. 30 Old but original resonators in Japan (Not bar and sphere) One of examples : Torsion detector (60 Hz) 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). 3.Outlines of detectors S. Kimura et al., Physics Letters A 81 (1981) 302. “Gravitational wave detection” Kyoto University Press (1998) Fig. 5-6. (Japanese)

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

32. 32 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. 3.Outlines of detectors

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

34. 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. 35 3.Outlines of detectors Sensitivity of interferometer 1 st generation (LIGO,VIRGO) 2 nd generation 3 rd generation 10 times 10 times ?

36. 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. 37 VIRGO (Italy and France) 3.Outlines of detectors 3 km, Pisa (Italy) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

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

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

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

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

42. 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. 43 3.Outlines of detectors AIGO (Australia) 8 km, Perth (Australia) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

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

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

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

47. World wide network for GW astronomy Adv. LIGO (under construction since 2008 ） TAMA/CLIO LCGT, Budget request LIGO(I) Hanford LIGO(I) Livingston GEO 600 Virgo AIGO (budget request) Adv. Virgo (design) ET (planed) A network of detectors is indispensable to position the source. LCGT By K. Kuroda (2009 May Fujihara seminar) GEO HF

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

49. 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. (1)Gamma ray burst (2) Crab pulsar (3) Stochastic background

50. 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. Nobody knows what they are and how much distances from Earth are. Gamma ray bursts appear suddenly and disappear soon.

51. 51 4.Recent results in observation (1) Gamma ray burst Revolutions in 1997 BeppoSAX (Italy, Netherlands) Wikipedia, English Identification of optical counterpart Measurement of distance (order of billion light years !) J. van Paradijs et al., Nature 386 (1997) 686. D.E. Reichart, Astrophysical Journal 495 (1998) L99. However, central engine is still unknown.

52. 52 4.Recent results in observation (1) Gamma ray burst There are two categories. Long gamma ray burst (more than 2 sec) Short gamma ray burst (less than 2 sec) Central engine of short gamma ray burst Compact binary coalescence ? Neutron star – Neutron star, Black hole – Neutron star If so, short gamma ray bursts generate gravitational wave !

53. 53 4.Recent results in observation (1) Gamma ray burst GRB070201 (1 February 2007) Direction : Andromeda galaxy (M31) 0.77Mpc (about 2 million light years) Only LIGO interferometers were in operation. B. Abbott et al., Astrophysical Journal 681 (2008) 1419.

54. 54 4.Recent results in observation (1) Gamma ray burst No signal was found ! This conclusion does not exclude current model in M31. However, some parameter regions are excluded. If GRB070201 is in M31, 1 solar mass < m 1 < 3 solar mass 1 solar mass < m 2 < 40 solar mass This parameter region is excluded at >99% confidence. B. Abbott et al., Astrophysical Journal 681 (2008) 1419.

55. 55 4.Recent results in observation (2) Crab pulsar Crab nebula Wikipedia, English Rotating neutron star in Crab nebula (Supernova in 1054) Spin down : Loss of rotation kinetic energy Upper limit of gravitational wave Asymmetry of pulsar generates gravitational wave. h<1.4*10 -24 One of the largest upper limits in pulsars

56. 56 4.Recent results in observation (2) Crab pulsar Crab nebula Wikipedia, English LIGO interferometers 9 months data (Nov. 2005 - Aug. 2006) h<2.7*10 -25 No signal was found ! Upper limit of gravitational wave Loss due to gravitational wave is less than 4% of total loss. 5 times smaller upper limit than that of spin-down B. Abbott et al., Astrophysical Journal 683 (2008) L45.

57. 57 4.Recent results in observation (3) Stochastic background Cosmological stochastic background gravitational wave could be generated in early universe. After that, D, He, Li were generated (in first three minutes of universe). We can observe quantity of generated these elements. Their quantities depend on the speed of universe expansion. If energy density of stochastic background gravitational wave was too much, speed of universe expansion was different from our expectation.

58. 58 4.Recent results in observation (3) Stochastic background So, energy density of stochastic gravitational wave background (around 100 Hz) must be 1.1*10 -5 times smaller than average density of universe. Big Bang nucleosynthesis

59. 59 4.Recent results in observation (3) Stochastic background LIGO interferometers : about 2 years data (Nov. 2005 - Sep. 2007) Correlation between 2 interferometers No correlation was found ! So, energy density of stochastic gravitational wave background (around 100 Hz) must be 6.9*10 -6 times smaller than average density of universe. 1.6 times smaller upper limit than that of Big Bang nucleosynthesis Some models of early universe are ruled out. B.P. Abbott et al., Nature 460 (2009) 990.

60. 60 5.Summary Nobody has detected gravitational wave directly. There are two kinds of motivation for direct detection; physics and astronomy. Resonant and interferometric detectors were constructed on Earth and are operated for observation. Some scientific null results have already been obtained. In near future, gravitational wave will be detected directly !

61. 61 Thank you for your attention ! Vi ringrazio molto per la vostra attenzione !