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W.-T. Ni Department of Physics National Tsing Hua University, and

Determining the dark energy equation of state from gravitational-wave (GW) observations of binary inspira ls. W.-T. Ni Department of Physics National Tsing Hua University, and Shanghai United Center for Astrophysics Shanghai Normal University weitou@gmail.com. Outline. Introduction

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W.-T. Ni Department of Physics National Tsing Hua University, and

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  1. Determining the dark energy equation of state from gravitational-wave (GW) observations of binary inspirals W.-T. Ni Department of Physics National Tsing Hua University, and Shanghai United Center for Astrophysics Shanghai Normal University weitou@gmail.com Dark Energy Equation & Binary Inspirals W-T Ni

  2. Outline • Introduction • Binaries • Classification of GWs and methods of detection (Modern Physics Letters A25, 922, 2010; ArXiv 1003.3899) • GroundandSpace GW detectors • Dark energy equation of state • Outlook Dark Energy Equation & Binary Inspirals W-T Ni

  3. Introduction • No confirmed experimental evidence for dark matter except gravity deficiency (no confirmed positive results for ground and space experiments) • No confirmed evidence for deviation from general relativity with cosmological constants • Supernovae as distance standards has problems • No direct detection of GW (Only inspirals from GW radiation for binary pulsars [Hulse-Taylor Nobel prize 1992]) • However, we do expect to detect GW on earth in 2015-2020 • And GW from supermassive binaries in space after 2020 and experimental determining the dark energy equation Dark Energy Equation & Binary Inspirals W-T Ni

  4. Determining the Hubble constant from gravitational wave observationsBernard F. SchutzNature323, 310-311 (25 September 1986) • Rort here how gravitational wave observations can be used to determine the Hubble constant, H0. • The nearly monochromatic gravitational waves emitted by the decaying orbit of an ultra–compact, two–neutron–star binary system just before the stars coalesce are very likely to be detected by the kilometre–sized interferometric gravitational wave antennas now being designed1–4. • The signal is easily identified and contains enough information to determine the absolute distance to the binary, independently of any assumptions about the masses of the stars. • Ten events out to 100 Mpc may suffice to measure the Hubble constant to 3% accuracy. • Now SPACE interferometers for Dark Energy Dark Energy Equation & Binary Inspirals W-T Ni

  5. Dark Energy Equation & Binary Inspirals W-T Ni

  6. Nearby sources and Cosmological sources Dark Energy Equation & Binary Inspirals W-T Ni

  7. Dark Energy Equation & Binary Inspirals W-T Ni

  8. LIGO instrumental sensitivity for science runs S1 (2002) to S5 (present) in units of gravitational-wave strain per Hz1/2 as a function of frequency Dark Energy Equation & Binary Inspirals W-T Ni

  9. In addition to adLIGO and adVirgo, LCGT construction started this year Dark Energy Equation & Binary Inspirals W-T Ni

  10. Dark Energy Equation & Binary Inspirals W-T Ni

  11. Complete GW Classificationhttp://astrod.wikispaces.com/file/view/GW-classification.pdf (Modern Physics Letters A 25 [2010] pp. 922-935; arXiv:1003.3899v1 [astro-ph.CO]) Dark Energy Equation & Binary Inspirals W-T Ni

  12. Here performed a more careful analysis by explicitly using the potential Planck CMB data as prior information for these other parameters. • Find that ET will be able to constrain w0 and wa with accuracies w0 = 0.096 and wa = 0.296, respectively. • These results are compared with projected accuracies for the JDEM Baryon Acoustic Oscillations (BAO) project and the SNAP Type Ia supernovae (SNIa) observations. Dark Energy Equation & Binary Inspirals W-T Ni

  13. More massive binaries, lower frequency detectors: SensitivitiesofGroundandSpaceInterferometers in one diagram AI Dark Energy Equation & Binary Inspirals W-T Ni

  14. Massive Black Hole Systems: Massive BH Mergers &Extreme Mass Ratio Mergers (EMRIs) Dark Energy Equation & Binary Inspirals W-T Ni

  15. 0.1mHz-1 Hz ~10Hz-kHz Dark Energy Equation & Binary Inspirals W-T Ni

  16. LISA LISA consists of a fleet of 3 spacecraft 20º behind earth in solar orbit keeping a triangular configuration of nearly equal sides (5 × 106 km). Mapping the space-time outside super-massive black holes by measuring the capture of compact objects set the LISA requirement sensitivity between 10-2-10-3 Hz. To measure the properties of massive black hole binaries also requires good sensitivity down at least to 10-4 Hz. (2020) Dark Energy Equation & Binary Inspirals W-T Ni

  17. S/C 1 (L4) 60 地球 (L3) S/C 2 L1 L2 60 S/C 3 (L5) ASTROD-GW Mission Orbit • Considering the requirement for optimizing GW detection while keeping the armlength, mission orbit design uses nearly equal arms. • 3 S/C are near Sun-Earth Lagrange points L3、L4、L5，forming a nearly equilateral trianglewith armlength260 million km（1.732AU）. • 3 S/C ranging interferometrically to each other. Earth Sun Dark Energy Equation & Binary Inspirals W-T Ni

  18. Weak-Light Phase Locking • To 2pWA.-C. Liao, W.-T. Ni and J.-T. Shy, On the study of weak-light phase-locking for laser astrodynamical missions, Publications of the Yunnan Observatory 2002, 88-100 (2002); IJMPD 2002. • To 40 fWG. J. Dick, M., D. Strekalov, K. Birnbaum, and N. Yu, IPN Progress Report42-175 (2008). Dark Energy Equation & Binary Inspirals W-T Ni

  19. Time-delay interferometry for ASTROD-GW • Using Planetary Ephemeris to numerically calculate the various solutions of Dhurandhar, Vinet and Rajesh Nayak for time-delay interferometry of ASTROD-GW to estimate the residual laser noise and compare. (G. Wang and W.-T. Ni) • Second generation solution (Dhrandhar, Vinet and Nayak): (i) n=1, [ab, ba] = abba – baab (ii) n=2, [a2b2, b2a2]; [abab, baba]; [ab2a, ba2b] (iii) n=3, [a3b3, b3a3], [a2bab2, b2aba2], [a2b2ab, b2a2ba], [a2b3a, b2a3b], [aba2b2, bab2a2], [ababab, bababa], [abab2a, baba2b], [ab2a2b, ba2b2a], [ab2aba, ba2bab], [ab3a2, ba3b2], lexicographic (binary) order Dark Energy Equation & Binary Inspirals W-T Ni

  20. Numerical Results (Wang & Ni) a - b [a, b] Dark Energy Equation & Binary Inspirals W-T Ni

  21. Numerical Results (Wang & Ni) [ab, ba] [abba, baab] Dark Energy Equation & Binary Inspirals W-T Ni

  22. Massive Black Hole Systems: Massive BH Mergers &Extreme Mass Ratio Mergers (EMRIs) Dark Energy Equation & Binary Inspirals W-T Ni

  23. A candidate sub-parsec supermassive binary blackhole system (Nature 2009)Todd A. Boroson & Tod R. Lauer • quasar SDSS J153636.221 044127.0 separated in velocity by 3,500 km/s. • A binary system of two black holes, having masses of 10^7.3 and 10^8.9 solar masses • Separated by 0.1 parsec with an orbital period of 100 years. Dark Energy Equation & Binary Inspirals W-T Ni

  24. Dark Energy Equation & Binary Inspirals W-T Ni

  25. Dark Energy Equation & Binary Inspirals W-T Ni

  26. NANOGrav: Science OpportunityExploring the Very-Low-Frequency GW Spectrum (The North American Nanohertz Observatory for GWs) • What is the nature of space and time? local spacetime metric is perturbed by the cumulative effect of gravitational waves (GWs) emitted by numerous massive black hole (MBH) binaries. the energy density of GWs? • How did structure form in the Universe? whether MBHs formed through accretion and/or merger events. • What is the structure of individual MBH binary systems? • What contribution do cosmic strings make to the GW background ? • What currently unknown sources of GW exist in the Universe? (Every time a new piece of the electromagnetic spectrum has been opened up to observations (e.g. radio, X-rays, and γ-rays), new and entirely unexpected classes of objects have been discovered.) Dark Energy Equation & Binary Inspirals W-T Ni

  27. NANOGrav and PTA expectations Dark Energy Equation & Binary Inspirals W-T Ni

  28. BH Coevolution with galaxies • S. Sesana, A. Vecchio and C. N. Colacino, Mon. Not. R. Astron. Soc.390, 192-209 (2008). • S. Sesana, A. Vecchio and M. Volonteri, Mon. Not. R. Astron. Soc.394, 2255-2265 (2009). Dark Energy Equation & Binary Inspirals W-T Ni

  29. Demorest et al white paper Summary • Given sufficient resources, we expect to detect GWs through the IPTA within the next five years. • We also expect to gain new astrophysical insight on the detected sources and, for the first time, characterize the universe in this completely new regime. • The international effort is well on its way to achieving its goals. With sustained effort, and sufficient resources, this work is poised to offer a new window into the Universe by 2020. Dark Energy Equation & Binary Inspirals W-T Ni

  30. probing the black hole co-evolution with galaxies Dark Energy Equation & Binary Inspirals W-T Ni

  31. ASTROD-GW has the best sensitivity in the 100 nHz – 1 mHz band and fills the gap ASTROD-GW Dark Energy Equation & Binary Inspirals W-T Ni

  32. Dark Energy Equation & Binary Inspirals W-T Ni

  33. Space GW Detectors • Space interferometers (LISA,28 ASTROD,29,30 ASTROD-GW,12,14 Super-ASTROD,31 DECIGO,32 and Big Bang Observer33,34) for gravitational-wave detection hold the most promise with signal-to-noise ratio. • LISA28 (Laser Interferometer Space Antenna) is aimed at detection of low-frequency (10-4 to 1 Hz) gravitational waves with a strain sensitivity of 4 × 10-21/(Hz) 1/2 at 1 mHz. • There are abundant sources for LISA, ASTROD and ASTROD-GW: galactic binaries (neutron stars, white dwarfs, etc.). Extra-galactic targets include supermassive black hole binaries, supermassive black hole formation, and cosmic background gravitational waves. • A date of LISA launch is hoped for 2020. More discussions will be presented in the next section. Dark Energy Equation & Binary Inspirals W-T Ni

  34. LISA LISA consists of a fleet of 3 spacecraft 20º behind earth in solar orbit keeping a triangular configuration of nearly equal sides (5 × 106 km). Mapping the space-time outside super-massive black holes by measuring the capture of compact objects set the LISA requirement sensitivity between 10-2-10-3 Hz. To measure the properties of massive black hole binaries also requires good sensitivity down at least to 10-4 Hz. (2020) Dark Energy Equation & Binary Inspirals W-T Ni

  35. Dark Energy Equation & Binary Inspirals W-T Ni

  36. Dark Energy Equation & Binary Inspirals W-T Ni

  37. Space GW detectors as dark energy probes • Luminosity distance determination to 1 % or better • Measurement of redshift by association • From this, obtain luminosity distance vs redshift relation, and therefore equation of state of dark energy Dark Energy Equation & Binary Inspirals W-T Ni

  38. Space GW detectors and Dark energy • In the solar system, the equation of motion of a celestial body or a spacecraft is given by the astrodynamical equation a=aN + a1PN + a2PN + aGal-Cosm + aGW + anon-grav • In the case of scalar field models, the issue becomes what is the value of w() in the scalar field equation of state: w() = p() / ρ(), where p is the pressure and ρ the density. • For cosmological constant, w = -1. • From cosmological observations, our universe is close to being flat. In a flat Friedman Lemaître-Robertson-Walker (FLRW) universe, the luminosity distance is given by dL(z) = (1+z) ∫0→z (H0)-1 [Ωm(1+z′)3 + ΩDE(1+z′)3(1+w)]-(1/2) dz′, where w is assumed to be constant. Dark Energy Equation & Binary Inspirals W-T Ni

  39. Summary • Binaries as distance indicators • Detection, LCGT, adLIGO, adVirgo: 2017 PTAs: about 2020 • ET sensitivities • Space detectors for Gravitational Waves • BHs coevolution with galaxies & PTAs • Dark energy equation via binary GW observations • Bright future with a lot of works Dark Energy Equation & Binary Inspirals W-T Ni

  40. Thank you! Dark Energy Equation & Binary Inspirals W-T Ni

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