Probing strong gravity when gravity waves
Nicolás Yunes
Illinois Center for Advanced Studies of the Universe
Department of Physics
University of Illinois at Urbana-Champaign

December 1st, 2023

21st Extreme Universe Online Colloquium

Nagoya University

Nico’s Graviteers

Extreme Universe Colloquium

Probing strong gravity when gravity waves

Illinois Center for
Advanced Studies ofthe Universe2

What is it that you do?
Gravity
TheoryBlack Holes
Experimental
Relativity

Neutron Stars
Nuclear Physics

Compact
Binaries

Gravitational
Waves
Particle
Physics[see e.g. Yunes, Miller & Yagi, Nature Reviews
Physics (2022) or Miller & Yunes, Gravitational
Waves in Physics and Astrophysics, IOP (2022)]

What “fundamental” physics have we/will we learn from gravitational wave observations?
Extreme Universe Colloquium

Probing strong gravity when gravity waves

3Extreme Universe Colloquium

Probing strong gravity when gravity waves

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Probing strong gravity when gravity waves

5[Credit: Teresita Ramirez / Geoffrey Lovelace / SXS Collaboration / LIGO Virgo Collaboration]
Extreme Universe Colloquium

Probing strong gravity when gravity waves

6FactThe future is loudCredit: LIGO

Challenge
So what are you going to
do with all this data?
Credit: https://observing.docs.ligo.org/plan/

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Probing strong gravity when gravity waves

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ABC of GWs

Probing
Fundamental
Physics
Into theUnknown
Extreme Universe Colloquium

Probing strong gravity when gravity waves

8What are gravitational waves and how are they generated?
eXtreme Gravity:

where gravity is(a) non-linear and(b) dynamical

Gravitational Waves (GWs):
Wave-like perturbationof the gravitational field.
Generation of GWs: Accelerating masses(t-variation in multipoles)
Propagation of GWs:
Light speed, weaklyinteracting, 1/R decay.
Extreme Universe Colloquium<latexit sha1_base64="N3eiIIpKkN70AmZ0zR13lzAbGF4=">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</latexit>

GW Spectrum: Kepler 3rd Law!

Probing strong gravity when gravity waves

f=2⇡s

G mtot=3r12sc61⇠
28G2 mtot
mtot
ABC of GWs

9What are the sources of gravitational waves?
SMBH Mergers

Cosmic Strings
Relic radiation

BH andNS
Binaries

Supernovae

Supe

Extreme Mass Ratio
Inspirals

Supermassive BH Binaries

10-16 Hz
10-16 HzIn ation Probe

100 years

yeardays

10-9 Hz
10-7 HzPulsar timing

10-6 Hzhours
10-4 Hz
Space detectors

Spinning NS

seconds

Binary Mergers

milliseconds

101 Hz103 Hz
Ground interferometers

Credit:CornishflExtreme Universe Colloquium

Probing strong gravity when gravity waves

ABC of GWs

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How do you extract information from gravitational waves?
Modelling 1. Create template “filters”
DataAnalysis

2. Cross-correlate filters & data
3. Find filter that maximizes the likelihood function.
Fouriertransformof data

Likelihood
functionℒ∝einner product

Extreme Universe Colloquium

1− 2 (s − hs − h)=e−2 ∫s̃( f ) − h̃( f, λ)⃗detector noise (spectral noise density)

Probing strong gravity when gravity waves

Sn( f )

2dftemplate param thatcharacterize system

template (projection ofGW metric perturbation)

ABC of GWs

11

Searching for needles in a haystack…

[Credit: Rohit Chandramouli]
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Probing strong gravity when gravity waves

ABC of GWs

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Thein inmatchedfilteringis crucial
Themodelmodelused
used
matchedfilteringis crucial

InspiralMergerRingdown[Credit: SXS Collaboration]

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Probing strong gravity when gravity waves

ABC of GWs

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ABC of GWs

Probing
Fundamental
Physics
Into theUnknown
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Probing strong gravity when gravity waves

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What is fundamental physics?

For this talk: “fundamental physics” are deviations from general relativity
that can be probed with gravitational waves

Extreme Universe Colloquium

Probing strong gravity when gravity waves

Probing Fundamental Physics

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Why probe “fundamental physics” when gravity waves?
Curvature
Strength

ExtremeGravity Tests

WeakField
Tests

Field
Strength

GWs probe eXtreme Gravity
Extreme Universe Colloquium

Probing strong gravity when gravity waves[Will, Liv. Rev., 2005, Psaltis,Liv. Rev., 2008, Baker, et al,Siemens & Yunes, Liv. Rev.
2013, Yunes, et al PRD 2016]
Probing Fundamental Physics

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How do we probe the modified gravity bestiary?

[Credit: Tessa Baker]
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Probing strong gravity when gravity waves

Probing Fundamental Physics

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A page
pagefrom
fromthethepastpast…
NordtvedtBekensteine.g. Shapiro timedelay δtmeasured

setHellingsNordtvedt
δt(γ, dclosest /R)= δtmeasured
Brans- and constrain γ
Dicke

BergmannWagoner

WillNordtvedt

Rastall

Model Vector-Tensor
MaIndependent Solar to c ppin
gonstraγ<System Test
10 −5into ωisDATA

Scalar-Tensor

Pure ScalarParametrized
Einsteinpost-Newtonian
WithdrowFrameworkMurduch[Nordtvedt & Will,1970s]

Ni

Papapetrou

Extreme Universe Colloquium

Bimetric

Modified Gravity

NordströmppN parameters
EinsteinNordström
affect observables
Fokkerδt(γ, dclosest /R)

LightmanLee

Rosen

BD >

mappe
40,d000

PageTupper
LittlewoodBergman
Rosen
YilmazProbing strong gravity when gravity waves

Stratified
LeeLightmannNi

Ni

Probing Fundamental Physics

18Tamingthethebestiary
Tamingbestiary
Do parameter
estimation andconstrain βppE

GW strain h+ and hDynamical×

Chern-Simons

Model
Independent
Gravitational
Wave Test

DATA

ppE parameters affect
GW observable
h+,×(m1, m2, …, βppE)(αsMa
to c ppin
gonsβptra
pE <in1−02mappiseGB 1/2 d to)<1.7 kmParametrized
post-EinsteinianFramework[Yunes & Pretorius,PRD 79 (2009)]

Extreme Universe Colloquium

Probing strong gravity when gravity waves

Probing Fundamental Physics

19Effectivelydeforming
deformingawaygeneralrelativity
Effectively
awayfromfrom
GeneralRelativity
Principle ofEquivalence

masslessspin-2 field

One example:

S=<latexit sha1_base64="(null)">(null)</latexit>

Z

Lorentz
InvariancepParity
Invarianceh2Diffeomorphism
Invariance

DispersionlessPropagation⇤g R + (@ ) + F ( ) (R R + GB + . . .)…

i

Test properties of General Relativity by constructing
theories that violate its pillars
Dynamical Chern-Simons

Scalar-tensor theories

Einstein-dilaton-Gauss-Bonnet[Yunes & Pretorius, PRD 80 (’09)][Endlich, Gorbenko, Huang, Senatore, JHEP 09 (’17)][Yunes & Siemens, Liv. Rev. in Rel (’13)]
Extreme Universe Colloquium

Probing strong gravity when gravity waves

Einstein-AEther theory

Horava gravity
Massive gravity…
Probing Fundamental Physics

20Calculate
observable theory
throughdeformationsof GR
Inspiral
withppE
post-Newtonian
outsideGeneral Relativity
I. Parametrically deform the Hamiltonian.
II. Parametrically deform the RR force.
III. Deform waveform generation.

H = HGR + δH

δH = αH v⃗ = F⃗⃗F RR+δF
RR,GRRRaH

δF ⃗aRR⃗
RR = α RRvh = F + h + + F⇥ h ⇥ + F s h s + . . .

IV. Parametrically deform g propagation.

22 4ã
E g = pg c + ↵˜ pg<latexit sha1_base64="(null)">(null)</latexit>

Result: To leading PN order and leading GR deformationah̃(f ) = h̃GR (f ) (1 + ↵f ) ei fb[Yunes & Pretorius, PRD 80 (’09)
Mirshekari, Yunes & Will, PRD 85 (’12)
Chatziioannou, Yunes & Cornish, PRD 86 (’12)]

Parameterized post-Einsteinian Framework
Extreme Universe ColloquiumProbing strong gravity when gravity wavesProbing Fundamental Physics

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Parameterized
post-EinsteinianParameterized
post-Einsteinian
test theoryah̃(f ) = h̃GR (f ) (1 + ↵f ) ei fb[Yunes & Pretorius, PRD 80 (’09)]

Mapping between
ppE parameters(β, b) to specificmodified theories[Cornish et al PRD 84 (’11), Gair & Yunes PRD 84 (’11), Chatziioannou et al PRD 86 (’12), Sampson et al PRD 87 (’13), Sampson, et al PRD 88 (’13), Sampson etal PRD 89 (’14), Huwyler et al PRD 91 (’14), Yunes, Yagi & Pretorius PRD 94 (’16), Tahura & Yagi PRD 98 (’16), Quiao et al PRD 100 (’19), Zhang et al PRD 100(’19), Moore & Yunes CQG 37 (’20), Bonilla, Kumar & Teukolsky (’22), Mezzasoma & Yunes PRD (’22), …]
Extreme Universe Colloquium

Probing strong gravity when gravity waves

Probing Fundamental Physics

22ppEconstraints
constraints with gravitational waves
ppE
Almostthesameas βh̃( f ) = h̃GR( f ) eiβfb

PN order (related to b)[LIGO, PRD 100 ’(19)]Anomalous

Acceleration

Extreme Universe Colloquium

Scalar Dipole
Radiation

Probing strong gravity when gravity waves

Lorentz
Violation

ParityViolation[Yunes, Yagi, Pretorius, PRD
94 ’(16), Editor’s suggestion]
Probing Fundamental Physics

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MappingppE
ppE
constraints
to specific
Mapping
constraints
to constraints
on theories
theories

Marginalized
posterior
distribution ofαEdGBFirst constraints on quadratic
gravity with gravitational waves!
p<latexit sha1_base64="/TP7scBDtAb5e7peswURslkVZVg=">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</latexit>

90% confidence
limit

αEdGB
for validity ofsmall coupling
approximation

Extreme Universe ColloquiumMax

Probing strong gravity when gravity waves↵EdGB  1.7 km[Nair, Perkins, Silva & Yunes,Phys.Rev.Lett. 123 (2019) 19, 191101,Perkins, Nair, Silva & Yunes,
Phys.Rev.D 104 (2021) 2, 024060,
Lyu, et al, Phys.Rev.D 105 (2022]

Probing Fundamental Physics

24ABC of GWs

ProbingFundamentalPhysics
Into theUnknown
Extreme Universe Colloquium

Probing strong gravity when gravity waves

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0PN

Understanding-0.5PN

0.5PN
1PN-1PN-1.5PN

1.5PN
EDGB-2PNh̃BD (f ; ~ GR ,LVh̃LV (f ; ~ GR , LV )2PN
MGBDBD )GR-2.5PN

CS

2.5PN
3PN

Gdot-3PNh̃D>4 (f ; ~ GR ,pp
E

D>4 )

h̃ppE (f ; ~ GR , ~ ppE )3.5PN-3.5PN
4PN-4PN
0”◆ ”

26

Beyond ppE tests of general relativity

Extreme Universe Colloquium

Probing strong gravity when gravity waves

Into the Unknown

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Neural post-Einsteinian (NPE) framework

Create training
set from ppEmodels

Encode into
D-reduced
latent space

Decode tominimize overlap
with training set

VAE-ppE should be able to:(i) detect (leading-PN order) ppE deviations ef ciently,(ii) detect untrained higher-PN order deviations,[Xi, Narayan &(iii) detect untrained non-polynomial deviations.
Yunes, in prep]
Probing strong gravity when gravity waves

Into the Unknown
fi

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NPE in action[Xi, Narayan & Yunes, in prep]
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Probing strong gravity when gravity waves

Into the Unknown

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Bayesian Parameter Estimation with NPE

distance from GR
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Probing strong gravity when gravity waves

type of GR deviation
Into the Unknown

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Summary and Outlook
Gravitational waves are beginning to place strong constraints on“fundamental” physics in extreme gravity

But what’s next?

Many more detections (stacking)Detectors with higher
sensitivity(2021-2028)

Look for new physics(e.g. screening mechanisms)
Look for physics in new sources(e.g. dipoles in EMRIs)

A few very loud detections(SNRs in low 100s)

Look at new agonistic tests(e.g. polarization tests)
and much more!

Extreme Universe Colloquium

Probing strong gravity when gravity waves

Into the Unknown

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Extreme Universe Colloquium

Probing strong gravity when gravity waves

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