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: Does not need a wave function collapse postulate.
* 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 developed by Everett and Wheeler for quantum cosmology, because of difficulties with the standard interpretation (Wheeler later changed his mind), based on a frequentist interpretation of probabilities; 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: Appears in short stories by Borges, and in F Hoyle's October the First Is Too Late (and in Star Trek)

Phenomenology > s.a. multiverse cosmology; quantum cosmology; quantum computing; semiclassical quantum mechanics [including macroscopic objects].
@ References: Zeh FP(73)qp/03 [and København]; Plaga FP(97)qp/95; Page qp/99 [consequences]; Yurov & Yurov ht/05 [cosmology].

References > s.a. measurement.
@ General: Everett RMP(57); Wheeler RMP(57); DeWitt in(68); Cooper & van Vechten AJP(69); 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); Deutsch in(86) [and experiment]; Fraïssé HPL(87); Tegmark FdP(98)qp/97 [vs others]; Ben-Dov AJP(90); Wallace SHPMP(02)qp/01 [world-view], SHPMP(03)qp/01 [and indefiniteness]; issue Nat(07)jul [50th anniversary].
@ And probabilities: Ballentine FP(73) [re derivation of statistical postulate]; Tappenden BJPS(00); Vaidman qp/01-in; Wallace SHPMP(03), BJPS(06); Rubin FP(03); Saunders qp/04; Van Wesep AP(06)qp/05; 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 [criticism of Deutsch-Wallace].
@ 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.
@ Against: Wheeler in(86); Kent IJMPA(90)gq/97; Byrne & Hall (99); Singh IJMPD(08)-a0705 [falsified by quantum gravity non-linearity].
@ Related topics: Squires FPL(88) [and paranormal effects]; Ben-Dov NCB(90) [and pilot wave]; 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]; > s.a. anthropic principle.

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"].

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Send feedback and suggestions to bombelli at olemiss.edu – Modified 21 jun 2008