Black-Hole Phenomenology |

**In General**
> s.a. gravitational phenomenology / astronomy;
higher-dimensional black holes; sources
of gravitational radiation.

* __History__: The idea of the
existence of black holes seemed reasonable only after the discovery of
pulsars in 1968.

* __Status__: 2005, Dozens of compact
objects with *M* > 3 *M*_{sun}
are known, and identified as black-hole candidates; Stellar ones, with
masses up to about 20 *M*_{sun}, are
found as unseen companions in low-mass X-ray binaries, the rest have masses
from a million to a billion *M*_{sun}
and are found in galactic nuclei; There is strong circumstantial evidence
that many of them have event horizons; 2017, So far observational proof
for black holes is impossible to come by.

* __Parameters__: The simplest
black hole parameter to measure is the mass; We do not expect to find black
holes with appreciable electric charge; A variety of methods are being tried
to estimate their spin parameters, such as the polarization of X-rays emitted
very close to the event horizon (in 1995 this was still not possible).

* __Remark__: The notion of
event horizon is a global one; The local analogs are those of trapped
surface, or isolated/dynamical horizon.

@ __Texts. Reviews__: Lasota SA(99)may;
Rees in(03)ap/04;
Cherepashchuk gq/05-conf [search];
van Putten 05;
Bilić PoS(06)ap [especially X-ray binaries];
Müller PoS(06)ap/07 [evidence];
Romero a0805-ln;
Czerny & Nikolajuk a0910-proc [masses];
Narayan & McClintock a1312-in [observational evidence];
Bailyn 14.

@ __Astrophysics__: Narayan NJP(05)ap;
Romero & Vila 14;
Merritt & Rezzolla ed-CQG(13)#24;
Haardt et al ed-16;
Bambi AdP(18)-a1711 [rev];
Capelo a1708-in;
Bambi a1906-conf [rev];
Bambi & Nampalliwar a1810-in;
Fabian & Lasenby a1911-in [rev];
Konoplya & Zhidenko a2001 [the parameters that matter].

@ __Falling in__: Tammelo & Kask GRG(97) [passage through horizon];
Krasnikov G&C(08)-a0804,
Augousti et al EJP(12) [pedagogical];
Creutz a2005-GRF [in different coordinates].

@ __Collisions, mergers__: Berti et al PRD(10)-a1003 [ultrarelativistic, scattering thresholds and gravitational radiation];
Gerosa & Berti PRD(17)-a1703 [and gravitational wave observations].

@ __ Rotating black holes__: Poisson PRD(09)-a0907 [tidal interactions];
Yang et al PRL(15)-a1402 [rapidly-spinning black holes, turbulent gravitational behavior];
Poisson PRD(15)-a1411 [tidal deformations];
Herdeiro & Radu IJMPD(15)-a1505-GRF [bound on rotation speed].

@ __Accelerating black holes__: Podolský et al PRD(03)gq [radiation, in Anti-de Sitter];
> s.a. c-metric.

@ __Nearly-extremal black holes__: Jacobson PRD(98)ht/97 [decay];
Garfinkle CQG(11) [infalling observers].

@ __Other types and theories__: Carballo-Rubio et al PRD(18)-a1809 [phenomenological parameters describing possible alternatives to black holes];
> s.a. brane-world gravity.

> __Types of phenomena__:
see binaries; matter and radiation near black holes
[including acceleration, jets, accretion disks]; gamma-ray astronomy.

**Stages in Black Hole Evolution**
> s.a. black-hole formation and radiation.

* __Evaporation__: After
black-hole formation, in addition to possible growth by accretion of
additional matter, the stages are (i) Balding, in which the black hole
loses its hair and becomes stationary; (ii) Hawking radiation, in which
the black hole shrinks; and (iii) Quantum gravity phase, about which we
still don't know much.

* __Hawking radiation__:
For small black holes, look for *γ*-rays over the background.

@ __General references__: Adams et al PLB(99) [effect of a cosmological constant on radiation];
Dalal & Griest PLB(00)ap [all eventually evaporate];
Ashtekar et al PRD(13)-a1306
[dynamics of horizon multipole moments and approach to the final state].

@ __Hawking radiation__:
Stephens PLA(89);
Rosu IJMPD(94)gq/96,
NCB(93)gq/95,
MPLA(93)gq/97,
MPLA(98),
G&C(01)gq/94.

**Detection and Observation**
> s.a. analogs [and mimickers]; binaries;
event horizons; types of black holes
[including microscopic]; supermassive black holes.

* __Observation__: A
stationary, isolated black hole, with no matter around it and no objects
in the background, cannot be seen; One with matter around it can be
identified by the behavior of the matter, although because of the infinite
gravitational redshift at the horizon, the horizon or the matter crossing
it will never be seen from the outside (what one can see instead is a
"frozen star"); One with objects behind it can be identified from its
lensing effects.

* __Candidates__: 2008,
There are many, in a range of masses from stellar ones to supermassive
ones in galactic cores, but no definitive evidence that they really are
black holes; Although some people say that it is possible to observe
effects arising from the presence of a horizon, the most convincing type
may be the detection of the specific frequencies predicted for quasinormal
modes, for example in ringdowns after mergers; 2016, We now know a few with
masses in the tens of solar masses, from gravitational-wave observations;
2020, The nearest of the couple dozen known black holes in our galaxy is
part of a triple system in Telescopium, 1000 ly away.

@ __Appearance__:
Ames & Thorne ApJ(68);
de Felice & Usseglio-Tomasset CQG(93) [orbiting];
Nemiroff AJP(93)jul-ap;
Stuckey AJP(93)may [surrounding objects];
Marck CQG(96)gq/95;
Zakharov et al gq/05-conf;
Vachaspati et al PRD(07)-gq/06 [from quantum collapse];
Zhang IJMPD(11)-a1003-conf [frozen stars];
Müller & Boblest AJP(11)jan [observer on a circular orbit around a Schwarzschild black hole];
Müller & Frauendiener EJP(12)-a1206 [thin disk around a Schwarzschild black hole];
Cardoso et al PRD(14)-a1406 [light rings as evidence];
news wired(14)oct [the movie *Interstellar*];
Nakao et al PRD(19)-a1809 [vs gravastars];
news sn(19)sep [visualizations];
Cardoso nRev(19)oct-a1910;
news sn(20)mar [photon subrings may be visible by telescopes in space];
Dokuchaev & Nazarova a2007 [M87* and SgrA*];
> s.a. black-hole geometry [interior].

@ __Imaging__: news sn(19)apr [using VLBI and the EHT],
sn(19)apr,
pt(19)apr [the black hole at the core of M87];
news Phys(20) [status].

@ __Radiation__: news cosmos(19)nov [from chaotic motion and reconnection of magnetic fields].

@ __Observation__: news cosmos(19)oct [the largest neutron star or smallest black hole seen];
news pw(20)may [nearest one];
Szybka a2011 [flyby].

@ __Determining black-hole spin__: Mukhopadhyay et al IJMPD(12)-a1210;
Pürrer et al PRD(16)-a1512 [from gravitational-wave observations].

@ __Testing the Kerr hypothesis__:
Bambi MPLA(11)-a1109,
PRD(12);
Bambi PRD(12)-a1204 [black-hole spin and power of steady jets];
Bambi JCAP(12)-a1205;
Bambi AR(13)-a1301 [with radio and X-ray data];
Li & Bambi JCAP(14),
Mizuno et al nAst(18)apr-a1804 [Kerr spin parameter and black-hole shadow];
Berti GRG-a1911 [topical collection].

@ __Shadows__: Abdolrahimi et al PRD(15)-a1502 [local];
Amarilla & Eiroa MG14(17)-a1512 [in alternative theories];
Younsi et al PRD(16)-a1607 [calculation method].

@ __Related topics__: Firouzjaee et al GRG(12)-a1010 [mass];
Fender et al MNRAS(13)-a1301 [how to search for the closest black holes];
Middleton ch(16)-a1507 [spin, theory and observation];
Lu et al MNRAS(17)-a1702 [evidence for event horizons];
> s.a. black-hole geometry [interior].

> __And other theories of gravity__:
see astrophysical tests of general relativity;
detection of gravitational waves;
massive gravity.

**Other Effects and Properties**
> s.a. astrophysics; matter
in kerr backgrounds [including overspinning]; spacetime subsets.

* __Rotating black holes__:
According to a calculation by K Thorne, the maximum value of *a*
allowed for a rotating (Kerr) black hole spun up by accreting matter is
0.998; This is a conservative bound, however, and more recent simulations
suggest that the limit is at most 0.93.

* __Retro-MACHOs__: A black hole
may act as a retro-lens which, if illuminated by a powerful light source,
deflects light ray paths to large bending angles, allowing us to detect
the black hole.

@ __Quantum gravity effects__: Flambaum gq/04 [particle and radiation phenomena];
Marolf GRG(10)-a1005-GRF [microphysics outside extreme or nearly extreme black holes];
Giddings PRD(14)-a1406 [possible observational windows];
Chen et al IJMPA(14)-a1410 [rev];
Giddings CQG(16)-a1602 [gravitational-wave tests];
> s.a. quantum black holes.

@ __General references__: Ruffini ap/98-proc [electromagnetic particle production];
Dimopoulous & Landsberg PRL(01)
+ pn(01)sep [in the lab?];
Jacobson & Sotiriou a1006-FQXi [on whether it is possible to destroy the event horizon];
Berti BJP(13)-a1302-TX [fundamental physics and strong-field gravity].

@ __As retro-MACHOs__: Holz & Wheeler ApJ(02)ap [Schwarzschild];
De Paolis et al A&A(04)ap,
Zakharov et al ap/04/A&A [Kerr].

@ __Frame dragging__:
Wex ap/99-conf;
Konno et al PRD(08)-a0807 [in Chern-Simons-modified gravity];
Herdeiro et al PRD(09)-a0907 [back-reaction];
Karas et al JPCS(12)-a1202 [on magnetic fields].

@ __Magnetosphere__: Ghosh MNRAS(00)ap/99;
Nathanail & Contopoulos ApJ(14)-a1404;
Lupsasca et al JHEP(14)-a1406 [force-free electrodynamics];
> s.a. kerr.

@ __Gravitational wave echoes__:
Cardoso & Pani a1707,
nAstr(17)-a1709 [evidence for horizons];
Cardoso et al a1902;
Saraswat & Afshordi a1906 [and fast scrambling];
Abedi & Afshordi a2001 [update on observational searches];
> s.a. black-hole geometry [firewall]; gravitational-wave
analysis [post-merger binaries].

@ __Related topics__:
Hsu PLB(02) [parity];
Gott & Freedman ap/03/PRD [life preserver];
Bekenstein in(03)gq [preparing a desired black hole];
news pw(08)apr [blazars];
Crane & Westmoreland a0908 [black-hole-powered spaceships];
Dokuchaev & Eroshenko AHEP(14)-a1403 [black-hole atoms];
Porto FdP(16)-a1606 [and the nature of spacetime];
Sorce & Wald PRD(17)-a1707 [black hole destruction];
> s.a. vacuum [vacuum decay nucleation sites].

> __And cosmology__:
see multiverse; variation of constants.

> __Related black-hole topics__: see black-hole geometry
[interior]; black-hole uniqueness; Mass Inflation.

> __Other related topics__:
see fine-structure constant;
Gyromagnetic Ratio; particle models;
quantum cloning; wormholes.

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