A xion S uperradian T instabilities BLASTs João G Rosa Aveiro University w ith Tom Kephart Vanderbilt University Phys Rev Lett 120 231102 2018 Editors Suggestion ID: 915697
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Slide1
B
lack hole
L
asers powered by Axion SuperradianT instabilities
BLASTs
João G. RosaAveiro Universitywith Tom Kephart (Vanderbilt University)Phys. Rev. Lett. 120, 231102 (2018) (Editors’ Suggestion)[arXiv:1709.06581 [gr-qc]]PACTS 2018, Tallinn, 21 June 2018
Gr@v
Slide2Lasers and stimulated emission
Kerr black hole
having a BLAST:
superradiant
instability
stimulated
axion decay
Slide3Black hole
superradiance
[
Zeldovich
(1966)]
Low frequency waves can be amplified by scattering off a Kerr black hole, extracting its energy and spin:
Slide4Klein-Gordon equation
in Kerr
space-time:
Separation of variables:stationary
and axisymmetric
spheroidal harmonicsSuperradiance for scalar waves
Slide5Schrodinger-like radial equation
:
where
ergoregion
event
horizonSuperradiance for scalar waves
Slide6I
II
General
solutions
:
Boundary conditions:Reflection coefficient: Toy model for superradiance
Slide7I
II
Toy model for
superradiance
In
the superradiant regime: negative phase velocity: positive group velocity:Waves carry negative energy into the BHEnergy and spin extraction from BH
Slide8Massive
fields can
become bound to the black hole:
“gravitational atoms”
[Arvanitaki et al. (2009)]gravitational potentialMassive black hole bombs
Slide9I
II
Bound
states
satisfy:In the limit :
Superradiant
instability
Toy model for superradiant instabilities
Slide10Superradiant instability
Massive scalar fields form
Hydrogen-like bound states
in Kerr BH:Exponentially growing field for leads to scalar cloudMain cloud properties:
[see review by
Brito, Cardoso & Pani (2015)]
Slide11QCD axion
Pseudo-scalar particle predicted by the
Peccei
-Quinn solution to the strong CP problemDecays into photon pairs:Can account for cold dark matter
(coherent oscillations, etc)
Slide12Stimulated decay important in dense axion clusters
[Tkachev (1987); Kephart
& Weiler (1987,1995)]
Boltzmann equation for axion decay/inverse decay:
where:
Axionic lasers
Slide13BH-axion-photon
system
Simplified model:
toroidal axion cloud (non-relativistic, flat space) homogeneous and isotropic phase space distributions
superradiance
spontaneous decayphoton escapestimulated decayphoton annihilation
Slide14Numerical
solution
Slide15Constraints
1. Critical cloud mass/spin for lasing:
PBHs born with no spin but can merge into spinning PBHs
2. Non-linear self-interactions quench instability (‘bosenova’)
Primordial BHs(dark matter?)[Kodama & Yoshino (2012-2015)]
Slide16BLAST phenomenology
Schwinger electron-positron pair production
increases photon plasma mass and quenches BLAST:
We should expect single lasing bursts:
Fast Radio Bursts?
[e.g. Chatterjee et al. (2017)]
Slide17BLAST phenomenology
Primordial BH merger rates (clustered scenario):
May have up to a few new
BLASTs formed per year in the sky!BLASTs
repeat every few hours after e+e- annihilation, yielding up to 10
8 FRBs before superradiance shuts downUp to 104 -105 active BLAST FRBs per day across the sky Other astrophysical signatures: e+e- annihilation/ positronium afterglows GWs from bosenova collapse in between bursts[Garcia-Bellido & Clesse (2016)]
Slide18Look for 10-5
eV QCD axion dark matter in the laboratory
+ DM axion-photon conversion in galactic B-field @ SKA
[Kelley & Quinn (2017)] ADMX, X3, CULTASK, MADMAX, ORPHEUS, …
Slide19Thank you!