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Bridging the Gap between Terrestrial Detectors and LISA

Bridging the Gap between Terrestrial Detectors and LISA. Elba 2002 May 24, 2002 Seiji Kawamura National Astronomical Observatory of Japan. Contents. Introduction What is DECIGO ? Science obtained by DECIGO Sensitivity of DECIGO Current Status of DECIGO Summary. 10 -18. 10 -20.

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Bridging the Gap between Terrestrial Detectors and LISA

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  1. Bridging the Gap between Terrestrial Detectors and LISA Elba 2002 May 24, 2002 Seiji Kawamura National Astronomical Observatory of Japan

  2. Contents • Introduction • What is DECIGO? • Science obtained by DECIGO • Sensitivity of DECIGO • Current Status of DECIGO • Summary

  3. 10-18 10-20 10-22 10-24 Gap between Terrestrial Detectors and LISA LISA Terrestrial Detectors Strain [Hz-1/2] (e.g. LCGT) Gap 10-4 102 100 104 10-2 Frequency [Hz]

  4. Importance of Bridgingthe Gap New window brings new science! • Observe inspiral sources that have moved above the LISA band • Observe inspiral sources that have not yet moved into the ground-based detector band • Completely new sources could be detected • Completely new science could be obtained

  5. How to bridge the gap? • Improve the low-frequency sensitivity of terrestrial detectors • Improve the high-frequency sensitivity of LISA • Build a detector suitable for the gap frequency  DECIGO

  6. 10-18 10-20 10-22 10-24 What is DECIGO? • Deci-hertz Interferometer Gravitational Wave Observatory • Space Antenna with short arm length LISA Terrestrial Detectors Strain [Hz-1/2] (e.g. LCGT) DECIGO (Sensitivity: Arbitrary) 10-4 102 100 104 10-2 Frequency [Hz]

  7. DECIGO • Named by T. Nakamura in the PRL paper by N. Seto, S. Kawamura, and T. Nakamura • Potential candidate for the future Japanese space antenna • Study of DECIGO just started; still primitive

  8. 10-18 10-19 10-20 10-21 102 100 10-4 10-2 Relationship between Sensitivity and Arm Length x100 f1 f-2 LISA Strain [Hz-1/2] DECIGO Force Noise: f0 f0:1/L (Arm Length: f0 XFN/L∝1/L 1/100 of LISA) x100 Shot Noise (f<f0): XSN/L∝P-1/2/L∝(L-2) -1/2/L=L/L Frequency [Hz]

  9. Advantages of DECIGO No confusion limiting noise above 0.1Hz (From the LISA report)

  10. Acceleration of Expansion of the Universe Expansion＋Acceleration? DECIGO GW NS-NS (z～1) Output Template (No Acceleration) Strain Real Signal ? Phase Delay～1sec (10 years) Time Seto, Kawamura, Nakamura, PRL 87, 221103 (2001)

  11. 10-18 10-20 10-22 10-24 10-4 102 100 104 10-2 10-26 Ultimate Sensitivity of DECIGO DECIGO (LISA Technology L=5×107m) LISA Terrestrial Detectors (e.g. LCGT) Strain [Hz-1/2] Ultimate DECIGO × 1000 (Necessary for acceleration measurement) Ultimate DECIGO (Quantum noise limited M=100kg, L=5×108m) Frequency [Hz]

  12. In the Paper, we said… The ultimate sensitivity of a space antenna in the far future could be, however, 310-27 around 0.1 Hz in terms of strain, assuming the quantum limit sensitivity for a 100 kg mass and an arm length of 1/10 of LISA. We name this detector DECIGO. This requires an enormous amount of effective laser power, and also requires that the other noise sources, such as gravity gradient noise, thermal noise, practical noise, etc. should be all suppressed below the quantum noise. Here we assume that such an antenna may be available by the end of this century.

  13. How to Improve Sensitivity? • Increase effective power - Increase the laser power - Increase the diameter of mirror • Use shorter wavelength? • Reduce other sensing noise • Reduce force noise • Solve confusion limiting noise problem

  14. DECIGO Working Group • NAOJ does not have a definitive plan after ALMA. • Convened in 2002 as one of WGs to study the future project candidates for NAOJ • 1st Meeting held on May 9, 2002 • 80 members currently involved • To be discussed in the 2nd Symposium (June 4-5, 2002) for NAOJ future projects

  15. Summary • It is important to bridge the gap between terrestrial detectors and LISA. • DECIGO is a candidate for the Japanese space antenna. • There is no WD-WD confusion limiting noise above 0.1 Hz. • DECIGO could measure the acceleration of expansion of the Universe. • DECIGO-WG has just started investigating the possibility.

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