Probing high-energy physics with gravitational waves from neutron star inspirals - Tanja Hinderer
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Probing high-energy physics with gravitational waves from neutron star inspirals Tanja Hinderer ? DeltaITP / GRAPPA University of Amsterdam Lorentz Center Leiden Oct, 26 2018
Overview Gravitational waves (GWs): a new tool for science Can extract a lot of information carried by GWs for binary systems credit: Most readily measurable imprints of source physics beyond vacuum GR BHs on GWs during an inspiral neutron stars as testbeds for our understanding of high-energy physics in unexplored regimes Credit: ESA/NASA Outlook ? Credit: LSC 1
Interpreting GW signals from binaries via matched filtering Data (GW150814) Model Distance: 800 Mpc Total Mass: 200 Msun simplified: only total mass and distance vary 2
Interpreting GW signals from binaries via matched filtering Data (GW150814) Model Distance: 800 Mpc Total Mass: 150 Msun simplified: only total mass and distance vary 2
Interpreting GW signals from binaries via matched filtering Data (GW150814) Model Distance: 800 Mpc Total Mass: 65 Msun simplified: only total mass and distance vary very sensitive to the phase 2
Interpreting GW signals from binaries via matched filtering Data (GW150814) Model Distance: 420 Mpc Total Mass: 65 Msun simplified: only total mass and distance vary very sensitive to the phase 2
Approaches to computing template models Newtonian dynamics orbital separation (1/velocity) post-Newtonian theory black hole more test path to merger perturbation relativistic particle theory limit + multi-scale Numerical expansions relativity mass ratio 3
Approaches to computing template models Newtonian dynamics orbital separation Effective one body (EOB) approach (1/velocity) combines all information to compute complete waveforms post-Newtonian theory Binary problem Effective description effective particle MAP test m1 path to merger (reduced mass) m2 black hole particle [Buonanno, Damour perturbation limit 1999, 2000] theory effective spacetime total mass M, mass ratio /M Numerical relativity EOB Hamiltonian + waveforms, GW dissipation + merger-ringdown mass ratio 3
Imprints of objects’ internal structure on GWs black holes (aligned spins) What changes for non-black hole objects? 4
Imprints of objects’ internal structure on GWs black holes other objects complex merger regime echoes, ringdown, tidal disruption, ≈ point-masses, postmerger, same signals … [outside sensitive [~103 cycles for few-Msun band for few-Msun objects in LIGO] objects in LIGO] 4
Imprints of objects’ internal structure on GWs black holes other objects complex merger regime echoes, ringdown, tidal disruption, rotational absence of postmerger, ≈ point-masses, deformations horizon … same signals tidal effects (absorption) [outside sensitive [~103 cycles for few-Msun + tidal excitation of internal band for few-Msun objects in LIGO] oscillation modes objects in LIGO] 4
Dominant tidal effects in GWs: characteristic parameter Tidal field Q= E (from companion’s Weyl tensor) Induced quadrupole tidal deformability =0 for a black hole [e.g. Kol & Smolkin 2011] • quantities defined by the asymptotic spacetime • Calculated from Einstein’s equations (perturbations to equilibrium structure) [TH 2008, Flanagan & TH 2008] Straightforward extension to higher multipoles Damour, Nagar 2009, Binnington, Poisson 2009 5
Neutron stars (NSs) debris from a supernova ▸ densest stable material objects known in the universe explosion in 1054 ▸ 1939: theoretical description [Oppenheimer & Volkoff] ▸ thousands observed to date Credit: NASA/ESA ▸ masses ≳ 1-2 solar masses (?), radii ~ 8-16 km (?) Crab Pulsar (neutron star rotating at 30 rev/sec) crushed to neutron-star crushed compactness Credit: NASA Black hole What is the physics in such extreme conditions? 5
Phases of QCD early universe Cartoon illustration Cartoon picture RHIC, LHC quark-gluon Temperature plasma ? ? ? hadrons ? ? ? nuclear ? NS mergers experiments neutron stars Baryon Density Credit: F. Linde 6
Conjectured Neutron Star (NS) structure [iron~10 g/cm3] crust ~ km neutron rich ions, ~106 g/cm3 inverse -decay Cartoon picture free neutrons ? ~1011 g/cm3 neutron drip outer core uniform liquid deep core ~1015 g/cm3 ~2-10x nuclear density exotic states of matter? deconfined quarks? signatures of new physics? ▸ many theoretical difficulties ▸ far extrapolations from known physics 6
Properties of NS matter reflected in global observables QCD phases Perturbations ? Equilibrium To equilibrium ? ? ?? ? R 8 NS matter models Mass vs. radius tidal deformability vs. mass (equations of state) 68 10 8 parameterλ λ(10 g cm s ) ■■■ 2 2 ■ ■■ ■ ■ ■■ ■■■■■■■ 2.5 ■■■■■ ■ 1 ■■■ 46 log [pressure] ■■■ mass (Msun) 36 ■ ■■ 6 ■ ■■ 2.0 ■ 0.100 ■ ■ 24 tidalparameter ■ 4 ■ 0.010 ■ 1.5 ■ 21.0 1.5 2.0 2.5 2 tidal 0.001 mass (Msun) ■■■ ■■■■ 1.0 ■■■ 1 5 10 10 11 12 13 14 1.0 1.5 2.0 2.5 log [density above nuclear] radius (km) 1.0 1.5 2.0 2.5 mass (Msun) mass (Msun) 2 = k2 R 5 dimensionless [TH+ 2010] 3 Love number 7
Effect of a phase transition to quark matter Perturbations QCD phases To equilibrium ? Equilibrium ? ? ?? ? R ⇤= m5NS Mass-radius Mass- Pressure-density [Paschalidis+ 1712.00451] + expect signatures in oscillation modes that can get tidally excited during inspiral 7
Influence on the GWs ▸ Energy goes into deforming the NS ⌦ ▸ moving tidal bulges contribute to gravitational radiation QNS = E tidal tidal (M ⌦)10/3 ▸ Imprint in GW phasing: GW ⇠ M5 M = m1 + m2 ▸ for NS-NS: most sensitive to the weighted average: [Flanagan & TH, 2008, Vines+ 2011] ✓ ◆ ✓ ◆ 1 m2 m1 ˜ = ⇤ 1 + 12 1 + 1 + 12 2 26 m1 m2 ▸ More sophisticated models incl. more details of NS’s tidal response available [Damour, Nagar, Bini, Faye, Bernuzzi, + , Steinhoff+/Hinderer+, Maselli+, Dietrich+, Kawaguchi+] 8
Measurements of tidal deformability for GW170817 ▸ Distance: ~40 Mpc, total mass: ~ 2.74 Msun ▸ Results for dimensionless tidal deformability ⇤ = m5NS Λ2 Λ1 Different GW models Λ2 LVC arXiv:1805.11579 90% contours Λ1 9
EoS results using restrictive assumptions low-spin priors
Examples of broader uses of tidal deformability ▸ nuclear equation of state, quark matter ▸ Other observables: ? ▸ astrophysics: NS radius ▸ Nuclear experiments: neutron skin thickness of lead 208 [Fattoyev+ 1711.06615] ▸ exotic objects [e.g. Cardoso, Pani,+, Sennett+, Johnson-McDaniel+, …] ▸ axions [e.g. Baumann+1804.03208, Brito+ 2018,…] ▸ dark matter halos [e.g. Nelson + arXiv:1803.03266v1] 11
Examples of new uses of cont.: QCD vacuum energy [Csaki+ arXiv:1802.04813] ▸ premise: cosmological constant originates from vacuum energy (VE) of QFT ▸ jumps at every phase transition by ~(Tc)4 ▸ Difficult to test in cosmology ▸ test with phases of the standard model with different vacuum expectation value of fields, e.g. QCD with CFL and non-CFL phases Effect on tidal deformabilities VE Different of smaller mass VE Vacuum energies ? CFL VE VE of larger mass 12
How sure are we that GW170817 was a NS-NS? New NR simulations ‣ Joint analysis of GW + EM counterpart information [F. Foucart,T.Vincent,+]: One-to-one comparison NS-BH Mass ratio Disfavored by nuclear physics NS-NS NS radius (km) TH, Nissanke, Foucart, Hotokezaka+ arXiv:1808.03836 relies on Foucart, TH, Nissanke 1807.00011 ‣ Only 60% of posterior probability distribution incompatible with NS-BH 13
Outlook ▸ Anticipated detector improvements ~2020: ▸ observe binary NSs ~ 2x further away (or at same distance with better accuracy) ▸ Improve high-frequency sensitivity by ~ factor of 5 ▸ Populations ▸ Measure subdominant effects? ? ? ? ? ? ▸ Oscillation modes - asteroseismology? ? ▸ Observe merger/postmerger, tidal disruption? ▸ Third-generation detectors: e.g. Einstein Telescope (possibly in NL) ~ 10x better sensitivity Expect a wealth of new insights in the coming years Will require significant further advances (modeling, analysis) 14
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