studying fundamental physics using current and future gravitational-wave detectors · 2019. 7....
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Studying Fundamental Physics Using Current and Future Gravitational-Wave Detectors
Martin Hendry
Institute for Gravitational Research
SUPA School of Physics & Astronomy
University of Glasgow, UK
Gravitational waves are ripples in spacetime propagating atthe speed of light (according to GR)
Created by acceleration of massive compact objects
Gravitational Waves: the Story So Far
In General Relativity gravity is described by the curvature of space-time
◼Matter tells spacetime how to curve.
◼Spacetime tells matter how to move
Gravitational wave detectors measure changes inthe separation between free test masses in thisspacetime
L+L
L-L
◼
Interferometers monitor the position of suspended test masses separated by a few km
A passing gravitational wave will lengthen one arm and shrink the other arm; transducer of GW strain-intensity (10-18 m over 4 km)
Interferometric Detectors
41016m
10-5m
GEO600TAMA, CLIO
LIGO Livingston
LIGO Hanford
4 km2 km
600 m300 m100 m
4 km
VIRGO 3 kmLIGO Livingston
Ground-based network of detectors: 2002-2010
From Initial to Advanced LIGO
Developed
in Glasgow,
UK supplied:
fused silica
suspensions,
fibre-pulling,
bonding and
welding
10kg test masses on simplependulums become 40kgmonolithic suspensions inquadruple pendulums, withbetter quality optics
GW150914 – a burst of gravitational waves…
… matching a BBH inspiral and merger waveform from General Relativity
Abbott, et al., LIGO Scientific Collaboration and Virgo Collaboration,
“Properties of the binary black hole merger GW150914”,
https://arxiv.org/abs/1602.03840
Does General Relativity really fit?
Compton Wavelength of the GravitonPost-Newtonian Approximation to GR
• GW150914 was the first observation of a binary black hole merger
• Our best test of GR in the strong field, dynamical, nonlinear regime
• Constraints better than the binary pulsar system PSR J0737-3039
Abbott, et al., LIGO Scientific Collaboration and Virgo Collaboration, “Tests of general relativity with GW150914”,
https://arxiv.org/abs/1602.03841
Further tests of General Relativity: GW170104 Abbott, et al., “GW170104: Observation of a 50-solar binary black hole coalescence at redshift 0.2”https://arxiv.org/abs/1706.01812
Parameterised test of PN expansion
Modified dispersion relation
Lower limit on QG energy scale
With three or more interferometers we can triangulate the sky position of a
gravitational wave source much more precisely.
Source
location
From Aasi et al., https://arxiv.org/abs/1304.0670
Advanced Virgo joined O2 on Aug 1st 2017
Much better sky localisation
Abbott, et al., LIGO Scientific Collaboration and Virgo Collaboration, “GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence”, https://arxiv.org/abs/1709.09660
Antenna patterns Likelihood function
p(Tensor)
p(Vector)
p(Tensor)
p(Scalar)> 200 > 1000
See also Isi et al. arxiv:1703.05730 and Abbott et al. arxiv:1709.09203:
First search for non-tensorial continuous GWs from known pulsars
Polarisation tests: GW170814
Abbott et al., “GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Binary Mergers Observed by LIGO and Virgo During the First and Second Observing Runs”, http://arxiv.org/abs/1811.12907
Improved Tests of GR With the GWTC-1 BBHsAbbott, et al., “Tests of General Relativity with the Binary Black Hole Signals from the LIGO-Virgo Catalog GWTC-1”arxiv.org/1903.04467
Abbott et al., “Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A”, https://arxiv.org/abs/1710.05834
Constraining the speed of gravity: GW170817
Tests of GR, nuclear EoS with GW170817
Abbott et al., “Tests of General Relativity with GW170817”,https://arxiv.org/abs/1811.00364
Abbott et al., “GW170817: Measurements of Neutron Star Radii and Equation of State”, https://arxiv.org/abs/1805.11581
Schutz, “Determining the Hubble Constant from gravitational wave observation”Nature, 323, 310 (1986)
Cosmology with Standard Sirens
Independent route to the Hubble Constant
Freedman, “Cosmology at a Crossroads: Tension with the Hubble Constant”, https://arxiv.org/abs/1706.02739
Tension between:
• Measurement of H0 from
cosmic distance ladder
(e.g. SH0ES)
• Inference of H0 from CMBR /
LSS and cosmological
model (e.g. Planck)
Tension increases in e.g.
Riess et al. 1903.07603:
Abbott et al. “A Gravitational Wave Standard Siren Measurement of the Hubble Constant“ Nature, 551, 85 (2017)https://dcc.ligo.org/public/0145/P1700296/005/LIGO-P1700296.pdf
Maximum posterior value
minimal68% C.I.
Can compare EM and GW luminosity distance –these scale differently in many higher-D models.
Adopt simple phenomenological model:
Number of spacetime dimensions: GW170817 Abbott et al., “Tests of General Relativity with GW170817”,https://arxiv.org/abs/1811.00364
Proximity of GW170817 limits effectiveness of constraints so far, but watch this space(-time)!…
Computed Bayesian posterior on D, fixing EM luminosity distance to Planck or SHoESHubble constant
Computed Bayesian posterior on D, for different fixed values of the screening scale
Pardo et al., “Limits on the number of spacetime dimensions from GW170817”, https://arxiv.org/abs/1811.00364
We can also use “dark sirens” – no explicit EM counterpart
We ‘marginalise’ over the redshifts of possible host galaxies
Soares-Santos et al., “First measurement of the Hubble constant from a dark standard siren using the Dark Energy Survey galaxies and the LIGO/Virgo binary black hole merger GW170814”, http://arxiv.org/abs/1901.01540
Useful ‘proof of concept’
GEO600 (HF)
Advanced LIGO
Hanford
Advanced LIGO
Livingston
Advanced
Virgo
LIGO-India
KAGRA
Network of advanced detectors
Coming attractions…
Nissanke et al., “Determining the Hubble constant from gravitational-waveobservations of merging compact binaries”, https://arxiv.org/abs/1307.2638
Coming attractions…
Chen et al., “Precision Standard Siren Cosmology”,https://arxiv.org/abs/1712.06531
Cowperthwaite et al., “Joint Gravitational Wave and Electromagnetic Astronomy with LIGO and LSST in the 2020s”, https://arxiv.org/abs/1712.06531
Third Generation GW Network
Aimed at having excellent sensitivity from ~1 Hz to ~104 Hz.
US-led project: “Cosmic Explorer” http://www.cosmicexplorer.org/
FP7 European design study: the
Einstein Telescope (ET).
Goal: 100 times better sensitivity
than first generation instruments.
See http://www.et-gw.eu/
See also Dwyer et al. arxiv: 1410.0612
https://gwic.ligo.org/3Gsubcomm/
~106 NS-NS mergers observed by 3G networks
Different models for spatial distribution,
source evolution
Cosmological constraints from 3G detectors
z
zwwzw a
++=
1)( 0
GW constraints similar to those from BAO, SNIe.
BUT assumes z known for ~1000 sources, z < 2
Significant ‘multi-messenger’ challenge
BNS: ET-D + CE
Zhao & Wen: http://arxiv.org/abs/1710.05325
See also Zhao et al. http://arxiv.org/abs/1009.0206
Assume we can measure flexion from
galaxy surveys, giving better estimate of
matter density on small angular scales.
EELT
Shapiro et al (2010): Shear varies spatially
Gradient of shear → arcing, or flexion
Correcting for Weak Lensing?...
Euclid
GW sources will be (de-)magnified by weak lensing due to LSS No correction
Shear map only, ELT
Shear + flexion, ELTShear + flexion,
ELT + Space
→ 1.8% at
→ 1.4% at EELT
LD 2=z
LD 1=z
Shapiro et al. arxiv:0907.3635
Space detectors
The Gravitational Wave Spectrum
Adapted from M. Evans (LIGO G1300662-v4)
10-9 Hz 10-4 Hz 100 Hz 103 Hz
Relic radiation
Cosmic Strings
Supermassive BH Binaries
BH and NS Binaries
Binaries coalescences
Extreme Mass Ratio
Inspirals
Supernovae
Spinning NS
10-16 HzInflation Probe Pulsar timing Ground based
Long tail due to
parameter degeneracies
Holz and Hughes 2005Colpi et al. 2019
LISA will ‘see’ very high-SNR massive black hole
binary mergers to z > 20
• Exquisite tests of GR from waveforms
• Standard siren Hubble diagram to high redshift
Extreme Mass Ratio Inspirals
• Among the most interesting and important low-frequency sources, probing fundamental physics, astrophysics and cosmology:
➢ Study immediate environment of MW-like MBHs at low redshift
➢ Perform precision tests of GR
➢ Explore multipolar structure of MBH gravitational fields
➢ Test GW propagation properties
➢ Measure cosmic expansion rate with GW observations alone (“dark sirens”)
➢ Probe dynamics of dense nuclear star clusters
Long, complex waveforms; major data analysis challenge!
Constraining extra-D models with LISA
Corman and Hendry (in prep.)
Realistic LISA data constrain well and .
But for better with steep transition.
Bayes factors strongly depend on errors,
weakly depend on MBH formation model
Heavy ‘seeds’, no delay
Strong Lensing of GWs?...
…Not yet, but clear future potential
For example: diagnostic of wave dark matter
Schive et al. “Cosmic structure as the quantum interference of a coherent dark wave”, arxiv:1406.6586
arxiv:1901.02674
A. Herrera Martin (2018)
“Wave dark matter as a gravitational lensfor electromagnetic and gravitational waves”
http://theses.gla.ac.uk/9027/
See also e.g. these arxiv papers on constraints from lensed GW+EM systems : 1901.10638; 1809.07079; 1703.04151; 1612.04095; 1508.05000
GWs and Primordial Black Holes?
Carr et al., https://arxiv.org/abs/1607.06077
arxiv:1603.00464
Abbott et al., http://arxiv.org/abs/1811.12907
Possible mass window in LIGO BH mass range?...
Useful discriminator could be isotropy of BH spins:• Random alignment for PBH origin models• Aligned distribution for other scenarios
Summary: Lots of coming attractions....
• Improved tests of GR:
➢ P-N orders; Compton wavelength➢ polarisation constraints (from ➢ speed of gravity – EM arrival, dispersion➢ EMRI mapping spacetime around SMBHs➢ joint GW-EM observations of lensed sources
• Constraining non-standard cosmologies:
➢ Hubble diagram of sirens; event rates➢ Primordial BHs – strong constraints from spin distribution➢ Strong lensing by DM haloes: probe of wave DM?➢ ????