Many-Worlds
Interpretation of Quantum
Theory |

**In General** > s.a. locality.

* __Idea__: Each of the possible
histories that contributes to the quantum amplitude for a process really exists,
so the wave function is a '"physical
thing" and provides a complete description of the system; Relatively
conservative interpretation, although it is not very intuitive and has some
conceptual problems.

* __Advantage__: It does not
need a wave-function-collapse postulate, and avoids the measurement problem by
considering every term in a quantum superposition as actual; With its elegant treatment of apparent wave function "collapse," it set the stage for applications of quantum theory such as decoherence, quantum computing, and quantum information.

* __Probability issue__:
If a history branches into finitely many possibilities (like an electron branching
into two outcomes of a Stern-Gerlach experiment) and each branch is "real," what
does it mean to say that it is more or less likely than another? Why doesn't
the simple counting measure work? If there are infinitely many branches and
any given one has probability zero,
why is it there at all? Some proposals have been made.

* __Branching issue__: How
does the branching work in a covariant view?

* __History__: 1957, initially
proposed in the PhD dissertation of Hugh Everett III, a student of Wheeler's, as the "relative state" formulation of quantum mechanics, for quantum cosmology, because of difficulties
with the standard interpretation (Wheeler
later changed his mind), and based on a frequentist interpretation of
probabilities;
Resurrected by DeWitt in 1970 and refined by Hartle, who related the probabilities to an inner
product structure;
1995, Saunders and the relationship between amplitudes and
probabilities;
1999, Deutsch and decision theory approach to deal with the
issue of probabilities.

* __And literature__: It appears
in short stories by Borges, and in F Hoyle's *October the First Is Too Late*
(and in *Star Trek*).

**Phenomenology** > s.a. quantum
computing; semiclassical quantum mechanics [including macroscopic
objects].

@ __General references__: Zeh FP(73)qp/03 [and
the København interpretation]; Plaga FP(97)qp/95;
Page qp/99 [consequences].

@ __Cosmology__:
Yurov & Yurov ht/05;
Aguirre & Tegmark PRD(11)-a1008 [infinite
universe]; Bousso & Susskind PRD(12)-a1105 + news tele(11)jun [and the multiverse]; Barrau EJTP-a1412; > s.a. multiverse
cosmology; quantum
cosmology.

@ __And experiment__: Deutsch in(86); Yun a1405 [double slit]; Gerig a1406 [proposed tests]; Deutsch a1508 [elimination of probabilistic concepts]; Päs IJQF-a1609 [probe in psychology?].

**References** > s.a. hidden variables; measurement in quantum theory [including quantum field theory].

@ __General__: Everett RMP(57);
Wheeler RMP(57);
DeWitt in(68); Cooper & van Vechten
AJP(69)dec;
DeWitt & Graham ed-73; Everett in(73); Geroch Nous(84);
Healey Nous(84); Smolin in(84); Stein Nous(84);
Mukhanov in(85); Whitaker JPA(85);
Fraïssé HPL(87); Tegmark FdP(98)qp/97 [vs
others]; Ben-Dov AJP(90)sep;
Wallace SHPMP(02)qp/01 [world-view],
SHPMP(03)qp/01 [and
indefiniteness]; issue Nat(07)jul
[50th anniversary]; Saunders et al ed-10; Barrett & Byrne ed-12; Marchildon SHPMP(15)-a1504 [spectrum of opinions]; Chen a1504 [mathematical formalism]; Sudbery a1601-in; Boughn a1801.

@ __History__:
Allori et al BJPS(11)-a0903 [Schrödinger's
first quantum theory as a precursor].

@ __And probabilities__: Ballentine FP(73)
[re derivation of statistical postulate]; Tappenden BJPS(00);
Vaidman qp/01-conf;
Wallace SHPMP(03),
BJPS(06);
Rubin FP(03);
Saunders in(05)qp/04;
Van Wesep AP(06)qp/05 [all phenomenological features of quantum observation are derivable from the many-worlds premise];
Hanson PRS(06)
[mangled worlds scenario and Born rule]; Price qp/06;
Wallace BJPS(06),
SHPMP(07)
[satisfactory]; Lewis SHPMP(07)
[uncertainty cannot be the ground for probability]; Baker SHPMP(07)
[Deutsch-Wallace argument is circular]; Hemmo & Pitowsky SHPMP(07)
[unsatisfactory]; Price a0802-conf
[criticism of Deutsch-Wallace]; Rae SHPMP(09)-a0810 [and
the Born rule]; Blood a0901;
Simon a0908 [conscious
observers]; Sudbery AIP(11)-a1009; Blood a1107; Hsu MPLA(12)-a1110 [intro]; Wilson BJPS(13) [avoiding the incoherence problem]; Carroll & Sebens ch(14)-a1405 [derivation of the Born Rule]; Saunders a1609-in [chance]; Mandolesi a1704; > s.a. Born Rule.

@ __Basis problem__: Ben-Dov FPL(90);
Stapp CJP(02)qp/01.

@ __In support__: Chalmers (96); Vaidman qp/96;
Sakaguchi gq/97;
Vaidman qp/00;
Tipler qp/00 [and
locality]; Tegmark Nat(07)-a0707;
Saunders & Wallace BJPS(08),
comment Tappenden BJPS(08),
reply BJPS(08)
[branching and diverging, meaning of uncertainty]; Tappenden BJPS(11); Bevers SHPMP(11); Wallace in(10)-a1111 [many worlds as emergent from the underlying theory through decoherence]; Duhamel & Raymond-Robichaud a1111; Page a1212 [theological argument]; Vaidman a1602-proc; Frauchiger & Renner a1604 [single-world interpretations cannot be self-consistent].

@ __Against__: Wheeler in(86); Kent IJMPA(90)gq/97;
Byrne & Hall PhSc(99); Singh IJMPD(08)-a0705 [falsified
by quantum gravity non-linearity]; Kent in(10)-a0905
[attempts at coherent accounts of probability]; Blood a1010 [fatally flawed]; Jeknić-Dugić et al a1012; Schwindt a1210; Edlam SHPMP(14)-a1504 [incoherence, the problem of confirmation]; Drezet a1502.

@ __And pilot-wave
interpretation__: Ben-Dov NCB(90); Valentini in(10)-a0811,
comment Brown a0901.

@ __And modal interpretation__: Domenech et al JMP(09)-a0904
[formal comparison]

@ __Related topics__: Squires FPL(88)
[and paranormal effects]; Barvinsky & Kamenshchik G&C(95)
[symmetries]; Rubin FPL(04)qp/03 [no
basis ambiguity]; Van Esch qp/05 [wave-function
collapse]; Rubin FP(06)
[spatial degrees of freedom]; Mallah a0902 [re
quantum immortality and quantum
suicide]; Mitra a0902-FQXi
[changing the past by forgetting]; Bondoni a1006-wd [concept of possibility]; Bradley BJPS(11) [and measurement]; Carter in(11)-a1203 [classical limit, and the anthropic principle]; Zeh NQ-a1211 [role of the observer]; Marchildon proc-a1704 [and spacetime]; > s.a. anthropic
principle.

> __Online resources__:
Wikipedia page;
Stanford Encyclopedia of Philosophy page.

**Variations**

@ __Many-minds__: Donald qp/97, qp/99;
Zeh FPL(00)qp/99;
Hemmo & Pitowsky
BJPS(03)qp/01 [probability
and non-locality].

@ __Other__: Squires EJP(87)
[many views of one world]; Mallah a0709 ["many
computations"]; Page a1102 ["many perceptions"]; Conroy SHPMP(12) [relative-facts interpretation]; Aerts & Sassoli de Bianchi FS(15)-a1406 ["many measurements"]; Hall et al PRX(14)-a1402 + news nat(14)oct ["many interacting worlds"]; Suarez a1712 ["all-possible-worlds", a unified reformulation of many-worlds and Copenhagen].

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jan 2018