1. Extracting Fundamental Physics from GW150914 (et al.)
A world-shaking discovery (literally)
Earth expands and contracts by the diameter of an atomic nucleus: cm

2. Gravitational Wave Spectrum

3. Probing Gravity: the Parameter Space
Size
Potential

4. Binary Pulsar Measurements
Particle Data Group

5. Fusion of two massive black holes
A new horizon in the study of the Universe
What does it tell us about fundamental physics?

6. GW150914: What was observed Very similar signals in the 2 detectors
In agreement with gravitational-wave predictions

7. The Gravitational Chirp …
… heard around the world
Frequency increases with time during inspiral
Consistency with general relativity  waves of different frequencies have same speed

8. GW150914 Constraint on Graviton Mass
Infall signal varies over range of frequencies O(100) Hz
Structure of signal maintained after propagation over ~ 400 Mpc
Gravitons of different frequencies ω propagate at same speeds v
: mg < 1.2 ✕ eV
Much less sensitive than indirect constraints from the dynamics of Galaxy clusters and weak lensing observations:
mg < 6 ✕ eV
More direct!
LIGO
PDG

9. The Graviton Mass = 0 in String Theory
Mass could be induced by dilaton tadpoles
Proof at one-loop level that these can be cancelled by tree-level counter-term
(Fischler-Susskind mechanism)
Formally, cancellation of dilaton tadpoles to all orders may be achieved, using complete normal ordering procedure applied to two-dimensional world-sheet field theory formulated on (resummed) higher-genus world-sheet surfaces
Minahan,1990
No need for supersymmetry!
JE, Mavromatos & Skliros, arXiv: & to appear

10. Direction in Sky (LIGO)
Search for electromagnetic counterpart
Direction in Sky (LIGO)

11. Direction in Sky (Fermi)
Search for electromagnetic counterpart
Direction in Sky (Fermi)

12. Electromagnetic Counterpart?
Many experiments looked for electromagnetic counterpart (light, radio, γ rays, X rays, …
All results negative
except for Fermi satellite
γ rays > 50 keV
Astrophysical puzzle
Tells us speeds of light
and gravitational waves
same to 10-17
JE, Mavromatos & Nanopoulos, arXiv: , …

13. Other Constraints on Graviton Velocity
Absence of gravitational Čerenkov radiation constrains velocity > light:
> c:
< c:
> c:
< c:
Yunes, Yagi & Pretorius, arXiv:

14. Space-Time Foam?

15. Nature of Quantum Gravity Vacuum
Expect quantum fluctuations in fabric of space-time
In natural Planckian units:
ΔE, Δx, Δt, Δχ ~ 1
Fluctuations in energy, space,
time, topology of order unity
“Space-time foam”
Induce Lorentz violation?
J.A.Wheeler

16. Probes of Lorentz Violation for Photons
Linear effect: Δv ~ E/EQG
Time delay from distant object:
Compare arrivals of photons of different energies from astrophysical source with small intrinsic δt
Gamma-Ray Bursters, pulsars, active galaxies, …
Typical
sensitivities:
Amelino-Camelia, JE, Mavromatos,
Nanopoulos + Sarkar: 1997

17. Fermi Collaboration: arXiv:0908.1832 [astro-ph]
Fermi Analysis of GRB
Redshift z = ± 0.003
γ energies up to 31 GeV
No hint of energy-dependent time delay
Lower limit on mQG depends sensitively on assumptions
mQG > 1.2 to 102 mP
Fermi Collaboration: arXiv: [astro-ph]

18. HESS Analysis of AGN Flareχ2
Search for linear Lorentz violation in Markarian 501 Flare in 2014
mQG > 2.3 mP
HESS Collaboration, arXiv:

19. Lorentz Violation in Graviton Propagation?
Probe linear dependence of graviton velocity on energy (frequency) ~ E, ω/M1
Simple-minded estimate - maximal effect on GW similar to that of graviton mass:
Order-of-magnitude result:
Many orders less sensitive than for γ, electron
But first constraint
Can be improved in merger of smaller objects
JE, Mavromatos & Nanopoulos, arXiv:

20. General Constraints on Lorentz Violation
General power-law modification of graviton dispersion relation:
Time delay
Between
LIGO sites
ω/M1
mg2
No cosmic-ray
Čerenkov rad’n
Yunes, Yagi & Pretorius, arXiv:

21. GW150914, GW & LVT151012
LIGO & Virgo, arXiv:

22. The Second Gravitational Chirp …
LIGO & Virgo, arXiv:
GW151226
Higher frequency: less sensitive to graviton mass
More sensitive to Lorentz violation:
JE, Mavromatos & Nanopoulos, arXiv: v2

23. Expected Masses, LIGO Sensitivity
Giudice, McCullough & Urbano, arXiv:
Expected Masses, LIGO Sensitivity
Expected masses
LIGO Sensitivity
GW151226
Seeing BH mergers first was to be expected

24. Inferred Black-Hole Masses
GW150914
GW151226
LIGO & Virgo, arXiv:

26. Area Law and Energy Conservation
Giudice, McCullough & Urbano, arXiv:
Area Law and Energy Conservation
Relation between area and black-hole mass:
Area (entropy) theorem:
Energy conservation:
Data consistent with
constraints:
GW150914
& LVT151012 O
Also GW151226 O

27. Could Black Holes be the Dark Matter?
Capela, Pshirkov & Tinyakov, arXiv:
Could Black Holes be the Dark Matter? NO

28. Exotic Compact Objects?
Giudice, McCullough & Urbano, arXiv:
Exotic Compact Objects?
LIGO Sensitivity depends
on compactness
C = M/R
Made of bosons
or fermions?
Free bosons:
Interacting bosons:

29. Super-Radiant Axion Emission?
Theoretically forbidden range in (M,J)
Distribution including measurement errors
Arvinataki, Baryakhtar, Dimopoulos, Dubovsky & Lasenby, arXiv:

30. Shear Viscosity of Empty Space?
Goswami, Mohanty & Prasanna, arXiv:
Shear Viscosity of Empty Space?
Could suppress propagation of gravitational waves over cosmological distances
Bound from GW150914:
Cf, Dark Matter model calculation:

31. Fundamental Physics from Ringdown
Extra damping?
Constrain magnitude as function of frequency and damping time
Gravastar?
Giudice, McCullough & Urbano, arXiv:

32. Detecting Gravitational Memory?
Detectable with enough events?
Residual strain after merger event
Lasky. Thrane, Levin, Blackman & Chen, arXiv:

33. Observe Horizon of a Black Hole?
Sagittarius A* black hole at galactic centre
Event Horizon Telescope can image shadow
(Very Long Baseline radio Interference array)
Test no-hair theorem via shape of shadow
Quantum effects near horizon of M87 BH?
Broderick, Johanssen, Loeb & Psaltis, arXiv:
Giddings & Psaltis, arXiv:

34. Towards Probes of Quantum Gravity?
Probe quantum fluctuations in metric near horizon of M87 BH?
Quantum fluctuations in emissions of pulsars passing near BH horizon?
Giddings & Psaltis, arXiv:
Estes, Kavic, Lippert & Simonetti, arXiv:

35. Future Step: Interferometer in Space

36. Search for Quantum Gravitational Waves
Generated by ‘Hawking radiation’ in quasi-de Sitter state during cosmological inflation

37. Was that you I heard just now, or was it two black holes colliding?