In General > s.a. Ether; mathematics; Ontology; physics [ultimate theories]; quantum locality; Reality; Structural Realism.
* Idea: Scientific realism is a view about things, events, processes, that are unobservable either because they are tiny or because they are past; One can define a realist theory as one describing a closed system entirely by means of entities and concepts pertaining to the system (as opposed to operationalism).
* Microphysical realism: The view that the only real entities and properties are found at the most fundamental level of nature.
@ General references: Rohrlich FP(96); Schmelzer gq/97; Isham & Butterfield IJTP(98) [presheaf loophole]; Matzkin EJP(02)qp; Grangier qp/03 [and holism]; Wilholt SHPMP(08) [XIX-century debates over atomism]; Singh a0805-ch [history]; Sánchez-Guillén & Vázquez a0903 [realist world view]; Franson JPA(12)-a1004 [constraint on realistic theories]; d'Espagnat FP(11)-a1101 ['open realism' as restoring a mind-independent reality]; Gisin IJQI-a1401, Bolotin a1401 [possible definition]; Müller a1712, a1712 [the physical world as emergent]; Boughn a1903 [the term "reality" should be avoided]; Vickers BJPS(18)-a1912 [defense of realism].
@ Arguments re local realism: Caser PLA(84) [condition]; Hoffmann FP(90); Bernstein FP(99) [against, simplified GHZ]; Santos qp/01, SHPMP(05) [pro]; Lan IJTP(08)qp/03 [EPR, pro], IJTP(08)qp/03 [superpositions and mixtures], JRLR(05)qp/03 [GHZ, pro]; Adenier AJP(08)feb-a0705 [re Mermin's argument].
@ Elements of reality: Peres FP(92); Marchildon FP(08)-a0802 [Lorentz-invariant]; Grinbaum a1007 [criterion based on algorithmic complexity]; Khalidi PhSc(11) [challenges to microphysical realism].
@ Philosophical: Leplin 97; Psillos BJPS(00) [status]; Turner SHPS(04) [abductive arguments]; McMullin PhSc(03)jul [van Fraassen's], response van Fraassen PhSc(03)jul; Lyons BJPS(06) [and dividing systems into constituents]; Sankey 08; Stanford BJPS(09) [the problem of unconceived alternatives]; Bynum M&M-a1303 [on Informational Structural Realism]; Nanay BJPS(13) [singularist semirealism]; Del Santo a1807 [Einstein and Bohm]; > s.a. philosophy of science.

In Quantum Theory > s.a. classical limit; foundations; hidden variables; histories in quantum mechanics; interpretations; relationship with classical mechanics.
* Idea: Realism in quantum mechanics is the view that physical objects have properties that exist even before they are measured.
* The problem: Local realism is untenable, because the Kochen-Specker theorem asserts the impossibility of assigning values to quantum observables (hidden variables) in a way that preserves functional relations between them (unless the state space is 2D).
* Loopholes, way out: One question is whether one can formulate a non-local, contextual, holistic one (see Bell's theorem); It has been claimed that realistic interpretations are wrong because some predictions derived from a mixture are different from the corresponding ones derived from a superposition state [but @ see Lan IJTP(08)qp/03]; Then there is the failure of Bell's theorem for Clifford algebra-based local variables.
* Tests: It has been argued that local realism can be tested by considering electroweak CP-violation parameters values in neutral pseudoscalar meson (K0) systems.
@ General references: in von Neumann 55; Gleason JMM(65); Bell RMP(66); Van der Merwe et al ed-88; d'Espagnat FP(90), qp/98; Home & Selleri JPA(91) [and kaon physics]; Reid PRA(00)qp, PRL(00)qp, qp/01 [and macroscopic fluctuations]; Dieks FP(05) [possibilities]; Belousek FP(05) [underdetermination in quantum mechanics]; Giuliani NCB(07)qp/05; Norsen FP(07)qp/06 [against the phrase 'local realism']; Stairs & Bub FP(06) [points of view and apparent conflicts]; Accardi & Khrennikov qp/06-proc [adaptive realism]; Vernette & Caponigro qp/06 ["physical quantity" and "physical reality"]; Gomatam a0708 [connection with observations]; Chaves & Fritz PRA(12) [entropic approach]; Vongehr a1207 [Randi challenge]; Cabello ch(16)-a1612 [non-realism as the key to quantum thory]; Freire & Angelo a1904 [degree of reality for continuous variables].
@ Realism is untenable: Leggett RPP(08); Bednorz NJP(15)-a1411; Lapiedra & Pérez a1503 [contradiction without inequalities]; Saldanha BJP(20)-a1805 [example].
@ Realism is tenable: Burgos FP(87) [in defense of realism]; Hájíček & Tolar a0802 [quantum mechanics does not contradict philosophical realism]; Laudisa FP(08)-a0811 [non-local]; Karakostas JGPS(12)-a1202; Hemmick & Shakur 12; Dorato & Laudisa a1401-in [various forms of realism, and instrumentalism]; Griffiths a1512; Hobson a1810, a1901 [realistic analysis of quantum issues]; Belinsky a1905; Raymond-Robichaud a2010 [local realistic model]; > s.a. realist interpretations.
@ Realism vs locality: Heywood & Redhead FP(83) [impossibility of reconciling]; Chiao & Garrison FP(99)qp/98; Chen & Zhu a0711; Jeong et al PRL(09)-a0806; Gisin FP(12)-a0901; Wechsler a0903-wd [and non-locality]; Hansson PRI(12)-a1104 [proposed test based on the Ruelle-Takens reconstruction method]; > s.a. quantum locality.
@ Hardy's theorem: Clifton & Niemann PLA(92) [and entangled spin-s particles]; Pagonis & Clifton PLA(92) [n spin-1/2 particles]; > s.a. relativistic quantum mechanics.
@ And measurement: Leggett & Garg PRL(85); Ballentine PRL(87), comment Leggett & Garg PRL(87); Percival & Garraway PLA(07)-a0706.
@ Other loopholes: Kracklauer qp/98 [abandon projection postulate]; Hess & Philipp PNAS(01) [time-correlated], comment Gill et al PNAS(02), Suarez qp/02; Malley PRA(04)qp [observables must commute]; Christian qp/07, qp/07, a0707 [Clifford algebra-based variables].
@ Tests: Genovese EPJC(05)qp [using CP-violation parameters]; Gröblacher et al Nat(07)-a0704 + pw(07)apr [non-local]; Suarez a0708 [non-local realism and before-before experiment]; Wilms et al PRA(08) [minimum detector efficiency to see violation]; Zhang et al PRA(13) [quantification]; Arora & Asadian PRA(15)-a1508 [with phase space measurements]; Shalm et al al PRL(15)-a1511 [loophole-free test].
@ Relativistic: Nikolić IJQI-a1002 [non-local reality compatible with relativity]; Kent PRA(14)-a1311, PTRS(14)-a1411, PRA(17)-a1608 [realist, one-world, relativistic framework]; Butterfield & Marsh JPCS(19)-a1902.
@ Related topics: Bohm & Hiley PRL(85) [in pilot-wave interpretation]; Jabs BJPS-a1212 [epistemological realism]; Miller PLA(96) [and t symmetry]; Vaidman FP(99)qp/98 [GHZ proof]; Nagata et al PRL(04) [constraints from rotational invariance]; Nagata JPSJ-a0705 [local realism and single qubit]; Stairs & Bub SHPMP(07) [and commutativity]; Morgan a0810 [random classical fields vs quantum fields]; Le Bihan SHPMP(09) [Bell inequalities and Fine's theorem]; Gisin a1012-conf [realism and randomness]; Lyre a1408 [Berry phase and ontic structural realism]; Dieks FP(19)-a1905 [Busch's 'unsharp quantum reality'].

Macroscopic Objects > s.a. macroscopic quantum systems.
* Macrorealism: A viewpoint which rests on two assumptions in conflict with quantum theory: An object of sufficiently large size is always in one place at a time (macroscopic superpositions can't exist) and the object's location can be determined without disturbing it; Leggett & Garg showed that if it were true, measurements performed at different times on an object could only be statistically correlated up to a certain degree, a relation they expressed mathematically through the Leggett-Garg inequality; Experimental results that violated this inequality would clearly show macrorealism to be false; Their work inspired a number of experiments; Later analyses have exposed loopholes in the Leggett-Garg argument, and provided other arguments against macrorealism.
@ General references: Reid & Deuar AP(98); Mohrhoff IJQI(04)qp [and spacetime]; Reid PRA(18)-a1612.
@ Macrorealism: Leggett & Garg PRL(85); Robens et al PRX(15) + Knee Phys(15); Clemente & Kofler PRA(15)-a1501; Allen et al Quant(17)-a1610 [no-go theorem].

main pageabbreviationsjournalscommentsother sitesacknowledgements
send feedback and suggestions to bombelli at – modified 29 oct 2020