GRAVITATIONAL WAVES. Eanna E. Flanagan Cornell University. Presentation to CAA, 30 April 2003 [Some slides provided by Kip Thorne]

Transcription

1 GRAVITATIONAL WAVES Eanna E. Flanagan Cornell University Presentation to CAA, 30 April 2003 [Some slides provided by Kip Thorne]

2 Summary of talk Review of observational upper limits and current and planned detectors. What are the science goals and opportunities of gravitational wave astronomy?» Ground based / space based» Near term / long term 2

3 Summary of Science Goals Probe gravity» Number of polarizations» Speed of waves» Mass of graviton» Frame dragging, tails» Bound scalar couplings Neutron star physics» Nuclear equation of state» Formation dynamics» Measure ellipticity» Crust/core coupling Other» Identify γ-ray burst sources?» Discover unexpected sources Probe of black holes» Population studies: M,a» Map geometry» Nonlinear dynamics of gravity Cosmology» Measure energy scale of inflation / disprove inflation» Probe dark energy?» Probe structure formation» Detect early Universe phase transitions, cosmic strings, Goldstone modes 3

4 Physical Nature of Gravitational Waves Ripples of curvature in the fabric of spacetime L / L = h Notation: Ω = 1 ρ d ln( de f ) d x f 100 Hz ( h ) 2 crit

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6 Overview of High Frequency Sources Neutron Star & Black Hole Binaries» inspiral» merger Spinning NS s» LMXBs» known pulsars» previously unknown NS Birth (SN, AIC)» tumbling» convection Stochastic background» big bang» early universe 6

7 Neutron Star / Neutron Star Inspiral (our most reliably understood source) 1.4 Msun / 1.4 Msun NS/NS Binaries Event rates» V. Kalogera et al, astro-ph/ ~10 min 20 Mpc 300 Mpc ~10,000 cycles ~3 sec Initial IFOs» Range: 20 Mpc» 1 / 3000 yrs to 1 / 3yrs Advanced IFOs -» Range: 300Mpc» 1 / yr to 2 / day 7

8 Science From Observed Inspirals: NS/NS, NS/BH, BH/BH Relativistic effects are very strong -- e.g.» Frame dragging by spins precession modulation» Measure wave tails, limit Branse-Dicke coupling, graviton mass Information carried:» Masses (a few %), Spins (?few%?), Distance [not redshift!] (~10%), Location on sky (~1 degree) M chirp = µ 3/5 M 2/5 to ~10-3 Search for EM counterpart, e.g. γ-burst. If found:» Learn the nature of the trigger for that g-burst» deduce relative speed of light and gw s to ~ 1 sec / 3x10 9 yrs ~

9 Neutron Star / Black Hole Inspiral and NS Tidal Disruption 1.4Msun / 10 Msun NS/BH Binaries Event rates» Population Synthesis [Kalogera] Initial IFOs» Range: 43 Mpc <~» 1 / 2500 yrs to 1 / 2yrs 43 Mpc inspiral 140 Mpc 650 Mpc Initial estimates suggest NS Radius measurable to 15%; infer eqn of state NS disrupt Advanced IFOs» Range: 650 Mpc <~» 1 / yr to 4 / day 9

10 Black Hole / Black Hole Inspiral and Merger 10Msun / 10 Msun BH/BH Binaries Event rates» Based on population synthesis Initial IFOs» Range: 100 Mpc <~» 1 / 300yrs to ~1 / yr Advanced IFOs -» Range: z=0.4 <~» 2 / month to ~10 / day 100 Mpc inspiral z=0.4 inspiral merger merger 10

11 BH/BH Mergers: Exploring the Dynamics of Spacetime Warpage 11

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13 Spinning NS s: Pulsars NS Ellipticity:» Crust strength e e < 10-6 ; possibly 10-5 ~ Crab Spindown Upper Limit Known Pulsars:» First Interferometers: e >~ 3x10-6 (1000Hz/f) x (distance/10kpc)» Narrowband Advanced e >~ 2x10-8 (1000Hz/f) 2 x (distance/10kpc) Unknown NS s - All sky search:» Sensitivity ~5 to 15 worse e = 10-5, 10kpc e = 10-6, 10kpc e = 10-7, 10kpc 13

14 Rotation rates ~250 to 700 revolutions / sec» Why not faster?» Bildsten: Spin-up torque balanced by GW emission torque Spinning Neutron Stars: Low-Mass X-Ray Binaries If so, and steady state: X-ray luminosity GW strength Sco X-1 Combined GW & EM obs s information about:» crust strength & structure Signal strengths for 20 days of integration 14

15 Neutron Star Births: Tumbling Bar; Convection Born in:» Supernovae» Accretion-Induced Collapse of White Dwarf If very fast spin:» Centrifugal hangup» Tumbling bar - episodic? (for a few sec or min)» If modeling gives enough waveform information, detectable to: Initial IFOs: ~5Mpc (M81 group, ~1 supernova/3yr) Advanced IFOs: ~100Mpc (~500 supernovae/yr) If slow spin:» Convection in first ~1 sec.» Advanced IFOs: Detectable only in our Galaxy (~1/30yrs)» GW / neutrino correlations! 15

16 Low Frequency Sources 16

17 Waves from Very Early Universe 17

18 Waves from Very Early Universe 18

19 Early Universe Waves Sources» Parametric amplification: inflation, bounce cosmologies» Preheating» Phase transitions» Cosmic strings» Kibble mechanism» Extra dimensions, branes.. Observational Handles» Energy spectrum» Detection of bursts» Non-Gaussianity» Non-stationarity» Non-isotropy 19

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22 Sensitivity to Dark Energy? Require recent (z<=1-2) GW sources Coalescing binaries are standard candles:» LISA can measure luminosity distance to SMBH binaries to 1%» Combine with electromagnetic measurement of redshift» Subject to systemic errors due to lensing. Alternative method: time variation of redshifts» Loeb (1998) showed dz/dt encodes cosmological information» Sato et. Al. (2001) suggested LISA follow on mission could measure dz/dt for many NS/NS binaries» Analog of lensing noise reduced by (v/c)^2. 22

23 Conclusion: Science Goals Probe gravity» Number of polarizations» Speed of waves» Mass of graviton» Frame dragging, tails» Bound scalar couplings Neutron star physics» Nuclear equation of state» Formation dynamics» Measure ellipticity» Crust/core coupling Other» Identify γ-ray burst sources?» Discover unexpected sources Probe of black holes» Population studies: M,a» Map geometry» Nonlinear dynamics of gravity Cosmology» Measure energy scale of inflation / disprove inflation» Probe dark energy?» Probe structure formation» Detect early Universe phase transitions, cosmic strings, Goldstone modes 23