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 . 6 M ⊙ 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 . 6 M ⊙ 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 10 49 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 10 43 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 occurring (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 B 0 will charge to Q = 2 B 0 J 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 B 0 will charge to Q = 2 B 0 J ...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 (10 49 ergs/s) and less for (non-repeating) FRBs (10 43 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 L EM -3 L GW 10 +0 + , + L EM L EM -4 10 + + + − + , 0 0.25 -5 10 + , − L -6 10 -7 0.20 10 -8 10 L 15 ◦ /L 90 ◦ + , + l =1 ,m =0 + , 0 l = m =1 + , − l = m =1 0.15 + , + l = m =2 + , − l =2 ,m =1 + , 0 l =1 ,m =0 -5 10 0.10 -6 10 l,m | φ 2 | 2 -7 10 0.05 -8 10 -9 10 0.00 400 300 200 100 0 100 400 300 200 100 0 100 t/M t/M 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): d 4 x √− g � � 2 − e − 2 α 0 φ F 2 � � � S = R − 2 ∇ φ φ — dilaton F — U (1) gauge field α 0 — positive real constant coupling α 0 == 0 — Einstein Maxwell coupled to free scalar field α 0 == 1 — low energy sector of string theory √ α 0 == 3 — Kaluza-Klein √ α 0 > 3 — not constrained Steven L. Liebling Doing the unexpected with binary black holes 10 / 23
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