In General > s.a. causality violations ["time machines"]; spacetime topology; wormhole solutions.
* Idea: Einstein-Rosen "bridges" or "handles," connecting either (i) different universes or regions of one universe (relativists' view), or (ii) two timelike related regions of a universe, representing the transient phenomenon of emission and reabsorption of a baby universe (hep theorists); Usually studied in the Euclidean regime.
* Motivation: Important because they represent non-perturbative features of quantum gravity; Interesting for two reasons,
- Macroscopic: Time travel (need exotic matter –enormous negative pressures– but could be made stable);
- Microscopic: They fix the constants of nature (Hawking – Consequences are unpredictable changes in the constants, loss of information down the holes; Coleman – Consequence is the big fix of the constants, in particular the cosmological constant; Unruh – All wrong, one must include more paths in the calculations).
* Remark: Wormholes appeared in an episode of "Star Trek: the Next Generation", 03.1990.
@ I: issue disc(89)jun; Halpern 92; in Thorne 94; Al-Khalili 11; news guard(13)jun [Kip Thorne and upcoming film]; news pbs(13)dec [microscopic channels between particles?].
@ II: Redmount NS(90)apr28; Clarke Nat(90); Simon PW(94)dec; Visser 95.
@ III: Bronnikov & Rubin 12.

Phenomenology > s.a. gravitational lensing; neutron stars; particle models.
* Possible observation: Bursts associated with their instability, or microlensing with unusual signature.
@ General references: Frolov & Novikov PRD(93) [as probes of black-hole interiors]; Kardashev et al IJMPD(07)ap/06; Damour & Solodukhin PRD(07)-a0704 [mimicking black holes]; Hyun et al a0705-wd [formation from gravitational collapse]; Dzhunushaliev et al JCAP(11)-a1102 [inside a star]; news sn(11)mar [Folomeev's proposal of phantom-matter-supported stellar wormholes]; Savelova & Kirillov a1405 [generation of an artificial wormhole]; James et al AJP(15)-a1502 [visualization].
@ And galaxies: Bambi PRD(13)-a1304 [and galactic centers]; Rahaman et al EPJC(14)-a1307 [in the galactic halo?].
@ Quasinormal modes: Konoplya & Zhidenko PRD(10)-a1004 [and scattering properties]; Konoplya & Zhidenko a1606 [ringing, vs black holes].
@ Particle and field propagation: González-Díaz PRD(97)gq [on electromagnetic waves]; Strokov & Repin a0709/G&C [perihelion precession and light deflection]; Shatskiy PU(09)-a0809 [characteristic features of images]; Pozanenko & Shatskiy G&C(10), a1007 [search for observational evidence in GRBs, soft-gamma repeaters]; Sarbach & Zannias AIP(12)-a1204; Tsukamoto et al PRD(12)-a1207 [lensing and Einstein-ring systems, vs black holes]; Li & Bambi PRD(14)-a1405 [using orbiting hot spots to distinguish black holes and wormholes]; > s.a. black-hole formation; types of dark matter.

Classical and Semiclassical Aspects > s.a. casimir effect; gravitational self-force; holography; quantum field theory effects [negative energies].
* Traversibility: It is accompanied by unavoidable violations of the weak energy condition ("exotic matter").
@ Framework: Friedman et al PRD(90) [Cauchy problem]; Hayward IJMPD(99)gq/98, gq/03-conf [dynamical laws].
@ And time machines: Frolov & Novikov PRD(90); Echeverría et al PRD(91); Antonsen & Bormann qp/96-proc; Aref'eva & Volovich IJGMP(08)-a0710 [production at the LCH].
@ Thermodynamics: Hong & Kim MPLA(06) [T < 0]; Martín-Moruno & González-Díaz CQG(09) [laws, thermal emission]; Bandyopadhyay et al IJTP(15)-a1211.
@ Other theoretical effects: Hochberg & Visser PRL(98)gq [null energy condition violation]; Cox et al a1109 [statistical mechanics of a gas of wormholes]; Olmo et al a1601-proc [as a cure for black-hole singularities]; Bejarano et al a1607 [and energy conditions].
@ Quantum field theory on wormhole background: Khatsymovsky PLB(94); Bezerra et al PRD(10) [massive scalar, vacuum stress-energy].
@ Semiclassical: Hawking NPB(91) [effective action]; Hochberg et al PRL(97)gq; Khusnutdinov & Sushkov PRD(02)ht [massive scalar]; Khusnutdinov PRD(03); Garattini CQG(05)gq [self-consistent to graviton 1-loop]; Buniy & Hsu PLB(06)ht/05 [instability]; Garattini & Lobo CQG(07)gq [phantom].
@ And chronology protection: Visser PRD(97)gq.

Quantum Aspects > s.a. entanglement in quantum field theory; kaluza-klein models [higher-dimensional dyons].
* Motivation: Used to explain the smallness of the cosmological constant, and as a mechanism for loss of coherence.
@ General references: Visser PRD(91), MPLA(91) [Planck-size throat]; González-Díaz MPLA(93); Hochberg PRD(95)gq [Lorentzian].
@ And constants of nature: Hawking NPB(90); > s.a. quantum gravity and cosmology [including cosmological constant].
@ And quantum gravity: Hawking MPLA(90), MPLA(90) [baby universes]; Kunstatter et al PRD(10), PRD(11)-a1010 [Einstein-Rosen throat]; Kuhfittig IJPAM(13)-a1301 [in non-commutative geometry]; > s.a. FLRW quantum cosmology; minisuperspace; quantum regge calculus; spacetime foam.
@ Black hole pair creation: Garattini NCB(98)gq/96; González-Díaz IJMPD(97)gq/96.
@ Related topics: Coleman & Lee NPB(90); Hawking & Page PRD(90) [spectrum]; González-Díaz PRD(90) [coherence]; Ellis et al PLB(90), Moss Nat(90)feb [in SQUIDs]; Garfinkle & Strominger PLB(91) [instanton for pair of Reissner-Nordström black holes]; Coleman & Hughes PLB(93) [global charge]; Cavaglià MPLA(94) [Kantowski-Sachs]; Lee & Kim PLB(04) [2D dilaton + ghost Klein-Gordon]; Santini qp/07-MGXI, EPL(07)qp [as origin of EPR correlations]; Garattini CQG(07) [traversable, and equation of state]; Engelhardt et al PRD(15)-a1504 [electric fields threading quantum wormholes].

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