| Event Horizons
> s.a. black holes / boundaries and
holography in field theory; quantum spacetime;
Rigidity; Trapped Surface.
$ Of a world-line: The past
(future) event horizon is the boundary of the future (past) of the world-line.
$ Of a spacetime: The boundary
of the past of \(\cal I\)+, \(\cal H\)
= ∂(I −(\(\cal I\)+))
(the future event horizon is the boundary of the future of \(\cal I\)−);
It is a global concept, defining from which points one can reach (null) infinity.
* Relationships: Its existence is equivalent to
\(\cal I\)− (\(\cal I\)+)
being spacelike (> see de sitter spacetime).
* Properties: They are
always null hypersurfaces; Their area always increases; They either
coincide or are outside the apparent horizon (not true?).
* Remark: Being global
properties, they are in general difficult to calculate, except when they
can be shown to coincide with a Killing horizon or some other locally
defined surface. [Defined by retarded time u = ∞.]
Baccetti et al a1706-GRF [existence?].
Geometry and Topology
> s.a. black holes; black-hole
types [toroidal]; topology change [censorship]
Related Topics > s.a. Firewall;
Fuzzball; gravitational thermodynamics.
@ Geometry: Chruściel et al AHP(01)gq/00 [area],
CQG(06)gq/05 [no degenerate components].
Huang & Liang PLA(95) [torus];
@ Related topics: Booth & Martin PRD(10)-a1007
[geometrical measure of the distance between apparent and event horizons, and Vaidya spacetime];
Chung PRD(11)-a1011 [dynamics of diffeomorphism degrees of freedom];
[dynamic changes in a black hole horizon as it forms and settles];
Shi & Mei PRD(17)-a1611 [extended BMS-like symmetries];
Barceló et al a2003 [without trapped surfaces].
* Thermodynamics: Thermal properties
of a static horizon (like its entropy or heat content) can be obtained either from
the surface term of the Einstein-Hilbert action or by evaluating the Noether charge,
corresponding to the diffeomorphisms generated by the timelike Killing vector field.
* Alternatives: To resolve some puzzles
arising from properties of quantum field theory in the presence of horizons, some
physicists have proposed that the equivalence principle (or "no drama"
scenario) does not hold near the surface of a black hole and the event horizon is
replaced by a "firewall" (Almheiri, Marolf, Polchinski, and Sully) which
would cause any observer who reaches the firewall to burn and not be able to cross
to the other side, or a "fuzzball", motivated by string theory.
Gibbons & Hawking PRD(77);
Fulling & Ruijsenaars PRP(87);
comment Raychaudhuri CQG(90);
Jensen PRD(95) [stability];
Massar & Parentani NPB(00)gq/99;
Padmanabhan IJMPD(04)gq [and gravity as elasticity];
Zhou et al PLB(07) [second law in accelerating universe];
Majhi & Padmanabhan EPJC(13)-a1302 [from infinitesimal coordinate transformations];
Widom et al a1602
[and gravitational vacuum tension];
> s.a. horizons.
@ And particle motion: Oliveira a1107 [velocity of test particles at the event horizon, pedagogical].
@ Horizon wave functions: Casadio a1310-proc [and effective gup];
Casadio et al PLB(16)-a1509 [in various dimensions].
@ Quantum effects:
Sorkin in(96)gq/97 [wrinkling below threshold scale];
Chapline et al IJMPA(03)gq/00 [phase transition];
't Hooft gq/04-ln [and quantum information];
Bojowald et al CQG(11) [definitions in modified spacetime structures];
[and computational complexity];
Alonso-Serrano et al PRD(14)-a1410 [unitarity is not preserved in individual regions separated by horizons];
[quantum corrections on horizon scale];
> s.a. correlations;
quantum black holes.
@ Other properties: Bergamin et al CQG(06)ht/05 [physical-to-gauge-degree-of-freedom conversion];
[what happens at the horizon].
@ In modified gravity theories:
Berglund et al PRD(12) ["universal horizon" mechanics].
@ Numerical methods: Libson et al PRD(96);
> s.a. numerical simulations of black holes.
@ Cosmological: Kaloper et al PLB(04) [observational implications].
@ Observational evidence:
Barbieri & Chapline PLB(12) [experimental signature for the absence of an event horizon];
Bambi SWJ(13)-a1205 [non-observation of radiation vs ergoregion instability];
Visser PRD(14)-a1407 [(non-)observability];
> s.a. black-hole phenomenology [including gravitational-wave echoes].
– journals – comments
– other sites – acknowledgements
send feedback and suggestions to bombelli at olemiss.edu – modified 24 mar 2020