Doing the unexpected with binary black holes ICERM Brown University - - PowerPoint PPT Presentation

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Doing the unexpected with binary black holes

ICERM Brown University

Steve Liebling

Work mentioned here with: John Estes (SUNY Westbury) Eric Hirschmann (BYU) Michael Kavic (SUNY Westbury) Luis Lehner (Perimeter) Matthew Lippert (SUNY Westbury) Carlos Palenzuela (UIB) John Simonetti (Virginia Tech.)

Long Island University, New York, USA

October 8, 2020

Steven L. Liebling Doing the unexpected with binary black holes 1 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Motivation

Testing GR

cosmic censorship GR alternatives exotic matter (scalar fields/axions, etc)

Understanding beyond standard model physics

dark energy quantum gravity

Understanding mysterious astrophysics

dark matter FRBs cosmology (PBHs, cosmic strings & monopoles)

Unclassified unknowns

Are we really “hearing” what we think or could it be something else? Any unknown degeneracies? Are we ready for more surprises? 2.6M⊙ compact object? concurrent EM event to BBH? Precursors?

Steven L. Liebling Doing the unexpected with binary black holes 2 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Motivation

Testing GR

cosmic censorship GR alternatives exotic matter (scalar fields/axions, etc)

Understanding beyond standard model physics

dark energy quantum gravity

Understanding mysterious astrophysics

dark matter FRBs cosmology (PBHs, cosmic strings & monopoles)

Unclassified unknowns

Are we really “hearing” what we think or could it be something else? Any unknown degeneracies? Are we ready for more surprises? 2.6M⊙ compact object? concurrent EM event to BBH? Precursors?

Steven L. Liebling Doing the unexpected with binary black holes 2 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

A few thoughts on “beyond GR”

Does anyone actually have faith in a particular GR alternative? Any particular theory seems simply a means to explore deviations (and perhaps test GR itself). The strongest motivation of any seem to be “low energy effective string theory” Exotic matter (the RHS of Einstein’s equations) is effectively a GR alternative (e.g. boson stars, gravastars, ECOs, BH mimickers generally) All these GR alternatives (DCS, EMD, EdGB, Horndeski) are classical theories. How do we model a quantum theory of gravity? Is there any ”low energy effective theory” that would find hydrogen’s electron states? spectral lines?

Steven L. Liebling Doing the unexpected with binary black holes 3 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

A few thoughts on “beyond GR”

Does anyone actually have faith in a particular GR alternative? Any particular theory seems simply a means to explore deviations (and perhaps test GR itself). The strongest motivation of any seem to be “low energy effective string theory” Exotic matter (the RHS of Einstein’s equations) is effectively a GR alternative (e.g. boson stars, gravastars, ECOs, BH mimickers generally) All these GR alternatives (DCS, EMD, EdGB, Horndeski) are classical theories. How do we model a quantum theory of gravity? Is there any ”low energy effective theory” that would find hydrogen’s electron states? spectral lines?

Steven L. Liebling Doing the unexpected with binary black holes 3 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

A few thoughts on “beyond GR”

Does anyone actually have faith in a particular GR alternative? Any particular theory seems simply a means to explore deviations (and perhaps test GR itself). The strongest motivation of any seem to be “low energy effective string theory” Exotic matter (the RHS of Einstein’s equations) is effectively a GR alternative (e.g. boson stars, gravastars, ECOs, BH mimickers generally) All these GR alternatives (DCS, EMD, EdGB, Horndeski) are classical theories. How do we model a quantum theory of gravity? Is there any ”low energy effective theory” that would find hydrogen’s electron states? spectral lines?

Steven L. Liebling Doing the unexpected with binary black holes 3 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Surprise: Fermi GBM Detection accompanying GW150914

Responding to aLIGO trigger, find sub-threshold, weak sGRB event 0.4 s after GW peak Duration of 1.0s with luminosity of 1049 erg/s Satellite not ideally situated for search Large swatch of sky to cover Not very convincing:

Not seen by other γ-ray detectors:

AGILE [1604.00955] INTEGRAL [1602.04180]

Statistical significance of coincidence less than three sigma No other candidate EM counterparts to BBH found since

Steven L. Liebling Doing the unexpected with binary black holes 4 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

BBH could still provide EM counterparts

[Ford,Fraschetti,Fryer,SLL,Perna,Shawhan,Veres,Zhang,1903.11116] reviews models which allow for such counterparts Better localization with improved detectors could find such counterparts Alternatively, the continued absence of counterparts can be used to argue for constraints on BH charge Instead of GW observations of BBH with no EM counterpart, perhaps there are EM observations without observed GW counterparts...

Steven L. Liebling Doing the unexpected with binary black holes 5 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

What is a Fast Radio Burst (FRB)?

Transient (few millisecond) radio burst 1043 ergs/s Dispersion suggests extragalactic (recent one localized to 3 billion lyrs away) Tens found to be repeating suggesting at least some subset of progenitors not cataclysmic Observations suggest a huge number of these

• ccurring (1 every 8 seconds somewhere in

sky) which tends to rule out ideas (unless one introduces multiple populations) Possible multi-messenger candidates for GW? 3G Detector source?

Steven L. Liebling Doing the unexpected with binary black holes 6 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

How could a black hole maintain a charge?

Dark matter might charge a black hole [Carodoso,etal,1604.07845] NS-BH binary might drive a current to BH, and then go supernova [Wald,PRD

1974]

BH w/ angular momentum J and external magnetic field B0 will charge to Q = 2B0J BHs might devour cosmological magnetic monopoles

[Stojkovic,Freese,hep-ph/0403248]

Steven L. Liebling Doing the unexpected with binary black holes 7 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

How could a black hole maintain a charge?

Dark matter might charge a black hole [Carodoso,etal,1604.07845] ...not clear how the hidden sector ultimately couples NS-BH binary might drive a current to BH, and then go supernova [Wald,PRD

1974] ...would quickly neutralize

BH w/ angular momentum J and external magnetic field B0 will charge to Q = 2B0J ...requires large external magnetic field BHs might devour cosmological magnetic monopoles

[Stojkovic,Freese,hep-ph/0403248] ...my favorite; cosmological implications

Steven L. Liebling Doing the unexpected with binary black holes 7 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Electromagnetic Luminosity of Charged BBHs

[SLL,Palenzuela,1607.02140]

Proposed by [Zhang,1602.04542] as source of hard X-rays from GW150914 & FRBs We studied evolution of equal mass, charged black hole coalescences Evolutions suggest q = Q/M ≈ 10−4 sufficient to power the Fermi Event (1049 ergs/s) and less for (non-repeating) FRBs (1043 ergs/s) Though relatively small, still absolutely big: Astrophysically such an electric charge difficult to sustain

Steven L. Liebling Doing the unexpected with binary black holes 8 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Luminosity of Magnetically Charged BBH in Force-Free Environment

10

• 8

10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

L LGW L EM

+ +

L EM

+0

L EM

+−

400 300 200 100 100

t/M

10

• 9

10

• 8

10

• 7

10

• 6

10

• 5

|φ2 |2

l,m

+, +l =1,m =0 +, +l =m =2 +,0l =1,m =0 +,0l =m =1 +,−l =m =1 +,−l =2,m =1

400 300 200 100 100

t/M

0.00 0.05 0.10 0.15 0.20 0.25

L15 ◦/L90 ◦ +, + +,0 +,−

Steven L. Liebling Doing the unexpected with binary black holes 9 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Einstein Maxwell Dilaton as a GR Alternative

[Hirschmann,Lehner,SLL,Palenzuela,1706.09875] [SLL,1910.12644]

Action (in the Einstein Frame): S =

• d4x√−g
• R − 2
• ∇φ

2 − e−2α0φF 2 φ — dilaton F — U(1) gauge field α0 — positive real constant coupling

α0 == 0 — Einstein Maxwell coupled to free scalar field α0 == 1 — low energy sector of string theory α0 == √ 3 — Kaluza-Klein α0 > √ 3 — not constrained

Steven L. Liebling Doing the unexpected with binary black holes 10 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Einstein-Maxwell-Dilaton (EMD) system

Inclusion of a scalar DOF allows for other (dipole) radiation channels not present in GR

Relevant quantity is the so called scalar monopole charge, φ1: φ − − − →

r→∞ φ0 + φ1

r

Expect binaries to tighten earlier than in GR:

...all else being equal... Energy radiated faster than GR Dilaton acts as something like a scalar gravity Extremal bound increases because of gravity plus dilaton balances electrostatic repulsion:Q2/M2 = 1 + α2

Steven L. Liebling Doing the unexpected with binary black holes 11 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Charged BBH in EMD

Initial data: quasicircular BBH, constant scalar field, BHs initially charged Q = 0.001 (mass ratios 1 and 1.5) For small charges, small differences Larger α regime numerically difficult, especially w/ magnetic charges Juli´ e predicts ‘steep scalarization’ with increased φ0 [1711.10769] GW PN predictions for BBH by Juli´ e [1809.05041] and Khalil, etal [1809.03109]

0.010 0.005 0.000 0.005 0.010

Re[rΨ2, 2

4 ]

2 4 6 8 10 12 14 16

%Diff|rΨ2, 2

4 |

[α0 = 1] − [α0 = 1000] [α0 = 1] − [α0 = 3000]

680 700 720 740 760 780 800 820

t/M

0.00 0.05 0.10 0.15

Mω

α0 = 1 α0 = 1000 α0 = 3000 Steven L. Liebling Doing the unexpected with binary black holes 12 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Looking for QG corrections Near BHs in BBHs

[SLL,Kavic,Lippert,1707.02299]

GR alternatives are still classical, but expect a quantum theory holds We want to be somewhat agnostic about what theory of gravity Nature has chosen But many constraints tell us that this true theory should be “close” to GR Many theories about near-horizon differences with GR. Not clear how best to model dynamically.

Steven L. Liebling Doing the unexpected with binary black holes 13 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Giddings-related work

Take as an example recent work by Giddings et al: [1602.03622] [1605.05341]

[1606.07814] [1701.08765] arguing/looking for effects of “corrections” near the

BH for EHT and LIGO Context is quantum gravity and the BH information paradox (e.g. fuzzballs and firewalls) Similar idea using Pulsar-BH binaries to test for such corrections [Estes,Kavic,Lippert,Simonetti, 1606.07814] Giddings proposes a general metric perturbation Hµν around the BH:

a spatial range, R, around the BH, comparable to BH radius a wavelength scale, L...soft (roughly size of horizon) a frequency ω = 1/ (8πM) or roughly inverse crossing time

Expects O (1) deviations from GR but only near BH

...compares to NS “modification” producing difference near merger

Steven L. Liebling Doing the unexpected with binary black holes 14 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Numerically Implementing These Fluctuations

Consider an equal mass, quasi-circular charged ++ BBH in electrovac 3 Parameters:

A — amplitude of perturbation R — radius of sphere of compact support from BH center ω — angular frequency of perturbation

Magnitude of perturbation: H = A exp−(

r− r1|2)

2/R2 sin (ωt)

where r1|2 denotes the location of the center of nearest BH Perturb diagonal components of metric: ˙ ˜ g00 → ˙ ˜ g00 (1 + H) ˙ ˜ gii → ˙ ˜ gii (1 − H)

Steven L. Liebling Doing the unexpected with binary black holes 15 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

10-7 10-6 10-5 10-4 10-3 10-2 10-1

|rΨ2, 2

4 |

0.08 0.06 0.04 0.02 0.00 0.02 0.04 0.06 0.08

Re[h]

300 250 200 150 100 50 50

t/M

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Mω

GR MΩ = 0. 1 MΩ = 0. 25 MΩ = 0. 5 MΩ = 0. 75 Steven L. Liebling Doing the unexpected with binary black holes 16 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Detectability

O(1, 2) = max 1|2

• 1|12|2

1|2 = Re ∞

−∞

˜ h1(ω)˜ h∗

2(ω)

S(ω) Overlap O for A MΩ M = 6M⊙ M = 20M⊙ M = 60M⊙ 0.05 0.1 0.997 0.996 0.996 0.1 0.1 0.999 0.999 0.999 0.5 0.1 0.694 0.764 0.827 0.5 0.25 0.757 0.802 0.840 0.5 0.5 0.492 0.599 0.692 0.5 0.75 0.517 0.616 0.702

Table : The overlap O between the GR waveform and the perturbed waveforms with amplitudes A and frequencies MΩ. Two waveforms are distinguishable by aLIGO if O 0.97.

Steven L. Liebling Doing the unexpected with binary black holes 17 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

BBH with superradiant axion clouds

[Kavic,SLL,Lippert,Simonetti,1910.06977]

If ultralight scalar field exists in Nature, highly spinning black hole will create superradiant cloud This cloud will subsequently decay via GW If in a binary, Its mass loss will tend to drive outspiral If large orbit, outspiral wins over inspiral from binary GW emission LIGO BBH mergers could constrain axions if we can establish that component BH was highly spinning in large orbit LISA offers potential to watch large orbits

Steven L. Liebling Doing the unexpected with binary black holes 18 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Superradiance

Probe BSM...existence of ultralight scalar fields Rotating BHs unstable to population

• f surrounding cloud if massive fields

exist Formation of cloud spins BH down until instability turns-off (saturation) Scalar cloud self-annihilates to GWs Existence of spinning BHs can exclude regions of parameter space...Regge plane

[Brito,et al,1501.06570]

Steven L. Liebling Doing the unexpected with binary black holes 19 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Motivation for Ultralight Fields

Fuzzy Dark Matter QCD Axions (e.g. Peccei-Quinn mechanism...breaking a global symmetry) String theory Axions (“axiverse” moduli compactification populates a mass spectrum) Hidden Sector: photons, massive gravitons Light (≪ eV), Bosonic, weakly coupled to SM

Steven L. Liebling Doing the unexpected with binary black holes 20 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Can one observe this in a BH-PSR?

Previous work with BH losing mass: ˙ a = −a

˙ MBH MBH+Mp

Using Pb = 10hours, MBH = 3M⊙, Mp = 1.4M⊙ Kepler’s 3rd Law: ˙ Pb = 2Pb

a ˙

a ˙ Pb = 0.04ms y−1

MBH+MP 4.4M⊙

−1

Pb 10h

α

0.07

16 0.04ms y−1 ≈ 1.4 × 10−12s/s which is about 103 times larger than precision with Hulse-Taylor binary Just GW emission would produce ˙ Pb = −0.0076ms y−1 Sensitive to 10−12eV ≤ µc2 ≤ 10−11eV

Steven L. Liebling Doing the unexpected with binary black holes 21 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Magnetized Primordial Black Holes In preparation by: Estes, Kavic, SLL, Lippert, Simonetti

Maldacena recently discusses magnetically charged BHs [Maldacena,2004.06084 For large charge, can restore electroweak symmetry in nearfield Much more stable than electrically charged:

Won’t be discharged by normal ambient matter Harder to pair produce magnetic monopoles because heavier

Near-extremal BHs greatly enhanced Hawking radiation proportional to charge Q

Brings the BH back to extremal Temperature decreases back to zero Opposite thermal behavior of Schwarzschild

Steven L. Liebling Doing the unexpected with binary black holes 22 / 23

Motivation Charged BBH Einstein-Maxwell-Dilaton BBH w/QG BBH w/axions mPBHs

Possible Implications of mPBHs

Standard model physics, but potentially expose high energy and quantum effects Interactions with stellar objects such as NSs? Engine for FRBs?

Steven L. Liebling Doing the unexpected with binary black holes 23 / 23