The Historical Development of Quantum Theory Jagdish Mehra Helmut Rechenberg The Historical Development of Quantum Theory VOLUME 6 The Completion of Quantum Mechanics 1926–1941 Part 2 The Conceptual Completion and the Extensions of Quantum Mechanics 1932–1941 Epilogue: Aspects of the Further Development of Quantum Theory 1942–1999 Subject Index: Volumes 1 to 6 LibraryofCongressCataloging-in-PublicationData Mehra,Jagdish. Thecompletionofquantummechanics,1926–1941/JagdishMehra,HelmutRechenberg. p. cm.—(Thehistoricaldevelopmentofquantumtheory;v.6) Includesbibliographicalreferencesandindex. ISBN0-387-95086-9(pt.1:alk.paper) 1. Quantumtheory—History. I. Rechenberg,Helmut. II. Title. QC173.98.M44 vol.6 530:12009—dc21 00-040039 Printedonacid-freepaper. (2001Springer-VerlagNewYork,Inc. 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PrintedintheUnitedStatesofAmerica. 9 8 7 6 5 4 3 2 1 ISBN0-387-95086-9 SPIN10771857 Springer-Verlag NewYork Berlin Heidelberg AmemberofBertelsmannSpringerScience(cid:135)BusinessMediaGmbH7 Contents—Part 2 Chapter IV The Conceptual Completion and theExtensions of Quantum Mechanics (1932–1941) 671 Introduction 671 IV.1 The Causality Debate(1929–1935) 678 (a) Introduction:ThePrincipleofCausalityinQuantumTheory 678 (b) Heisenberg’sDiscussionsConcerningthePositivismofthe‘Vienna Circle’(1929–1932) 683 (c) TheIndeterminacyRelationsforRelativisticQuantumFields (1929–1933) 692 (d) TheContinuationoftheDebateonCausalitywiththeBerlin Physicists(1929–1935) 703 IV.2 The Debateon the Completeness of Quantum Mechanicsand Its Description of Reality (1931–1936) 713 (a) Introduction 713 (b) FromInconsistencytoIncompletenessofQuantumMechanics: TheEPRParadox(1931–1935) 717 (c) TheResponseoftheQuantumPhysicists,Notably,Bohrand HeisenbergtoEPR(1935) 725 (d) ErwinSchro¨dingerJoinsAlbertEinstein:TheCatParadox(1935– 1936) 738 (e) RealityandtheQuantum-MechanicalDescription(1935–1936) 747 IV.3 New Elementary Particles in Nuclear and Cosmic-Ray Physics (1929–1937) 759 (a) Introduction:‘PureTheory’Versus‘ExperimentandTheory’ 759 (b) TheTheoreticalPredictionofDirac’s‘Holes’and‘Monopoles’ (1928–1931) 772 (c) TheDiscoveryofNewElementaryParticlesofMatterand Antimatter(1930–1933) 785 (d) QuantumMechanicsoftheAtomicNucleusandBeta-Decay (1931–1934) 801 (e) UniversalNuclearForcesandYukawa’sNewIntermediateMass Particle(1933–1937) 822 IV.4 Solid-State,Low-Temperature, and RelativisticHigh-Density Physics (1930–1941) 837 (a) Introduction 837 (b) NewAmericanandEuropeanSchoolsofSolid-StatePhysics (1933–1937) 840 vi Contents (c) Low-TemperaturePhysicsandQuantumDegeneracy(1928–1941) 857 (d) TowardAstrophysics:MatterUnderHighPressuresandHigh Temperatures(1926–1939) 877 IV.5 High-EnergyPhysics:Elementary Particles and Nuclear Reactions (1932–1942) 898 (a) Introduction 898 (b) BetweenHopeandDespair:ProgressinQuantum Electrodynamics(1930–1938) 902 (c) NewFieldsDescribingElementaryParticles,TheirProperties,and Interactions(1934–1941) 935 (d) NuclearForcesandReactions:Transmutation,Fusion,and FissionofNuclei(1934–1942) 964 Epilogue:Aspects ofthe Further Developmentof QuantumTheory (1942–1999) 1015 1. The ElementaryConstitution of Matter: Subnuclear Particles and Fundamental Interactions 1020 1.1 SomeProgress in Relativistic QuantumField Theory and the Formulation of the Alternative S-Matrix Theory (1941–1947) 1024 (a) E.C.G.Stueckelberg:‘NewMechanics(1941)’ 1024 (b) ThePrincipleofLeastActioninQuantumMechanics(Feynman andTomonaga,1942–1943) 1024 (c) Heisenberg’sS-Matrix(1942–1947) 1030 1.2 The Renormalized Quantum Electrodynamics (1946–1950) 1033 (a) TheShelterIslandConference(1947) 1033 (b) HansBetheandtheInitialCalculationoftheLambShift(1947) 1038 (c) TheAnomalousMagneticMomentoftheElectron(1947) 1043 (d) ThePoconoConference(1948) 1051 (e) VacuumPolarization(1948) 1057 (f) TheMichiganSummerSchool:FreemanDysonatJulian Schwinger’sLectures(1948) 1059 (g) TheImmediateImpactofSchwinger’sLectures(1948) 1062 (h) Schwinger’sCovariantApproach(1948–1949) 1064 (i) GaugeInvarianceandVacuumPolarization(1950) 1074 (j) TheQuantumActionPrinciple(1951) 1081 (k) TomonagaWritestoOppenheimer(April1948) 1085 (l) Tomonaga’sPapers(1946–1948) 1086 (m) Feynman’sPreparationsupto1947 1088 (n) RichardFeynmanaftertheShelterIslandConference(1947– 1950) 1091 (o) FreemanDysonandtheEquivalenceoftheRadiationTheories ofSchwinger,Tomonaga,andFeynman(1949–1952) 1099 (p) TheImpactofDyson’sWork 1104 (q) FeynmanandSchwinger:CrossFertilization 1106 1.3 New Elementary Particles and TheirInteractions (1947–1964) 1107 1.4 The Problems of Strong-InteractionTheory: Fields, S-Matrix, Currents, and the Quark Model (1952–1969) 1118 Contents vii 1.5 The ‘Standard Model’ and Beyond(1964–1999) 1125 (a) The‘ElectroweakTheory’(1964–1983) 1126 (a1) The‘IntermediateWeakBoson’ 1126 (a2) SpontaneousSymmetry-BreakingandtheHiggsMechanism 1127 (a3) TheWeinberg–SalamModelandItsRenormalization 1127 (a4) NeutralCurrentsandtheDiscoveryoftheWeakBosons 1128 (b) QuantumChromodynamics(QCD)(1965–1995) 1130 (b1) TheDiscoveryofPhysicalQuarks 1130 (b2) AsymptoticFreedomofStrongInteractionForces 1131 (b3) QuantumChromodynamics 1132 (b4) TheCompletionofQCD 1133 (c) BeyondtheStandardModel(1970–1999) 1134 2. Quantum E¤ects in the PhysicalLaboratory and in theUniverse 1138 2.1 The Industrialand Celestial Laboratories (1947–1957) 1139 (a) TheTransistorintheIndustrialLaboratory(1947–1952) 1139 (b) TheCelestialLaboratory(1946–1957) 1143 2.2 The Application of Known QuantumE¤ects (1947–1995) 1145 (a) TheCasimirE¤ectandItsApplications(1947–1978) 1145 (b) TheMaserandtheLaser(1955–1961) 1153 (c) TheBose-EinsteinCondensation(1980–1995) 1156 2.3 Superfluidity, Superconductivity,andFurther Progress in Condensed Matter Physics (1947–1974) 1159 (a) RotonsandOtherQuasi-Particles(1947–1957) 1159 (b) TheSolutionoftheRiddleofSuperconductivity(1950–1959) 1163 (c) CriticalPhenomenaandtheRenormalizationGroup(1966–1974) 1170 2.4 New Quantum E¤ects in Condensed Matter Physics (1958–1986) 1173 (a) TheMo¨ssbauerE¤ect(1958) 1173 (b) ExperimentalProofofMagneticFluxQuantization(1961) 1175 (c) TheJosephsonE¤ect(1962) 1176 (d) SuperfluidHeliumIII:PredictionandVerification(1961–1972) 1177 (e) TheQuantumHallE¤ectandLowerDimensionalQuantization (1980) 1179 (f) High-TemperatureSuperconductors(1986) 1181 2.5 Stellar Evolution, the NeutrinoCrisis, and 3 K Radiation (1957– 1999) 1183 (a) StellarEvolutionandNewTypesofStars(1957–1971) 1185 (b) TheSolarNeutrinoProblemandtheNeutrinoMass(1964–1999) 1187 (c) 3KRadiationandtheEarlyUniverse(1965–1990) 1190 3. New Aspectsof the Interpretationof Quantum Mechanics 1193 3.1 The Copenhagen InterpretationRevisitedand Extended (1948– 1966) 1197 3.2 Causality, Hidden Variables, and Locality (1952–1968) 1208 (a) TheHiddenVariablesandvonNeumann’sMathematical DisproofRevisited(1952–1963) 1212 viii Contents (b) TheEPRParadoxRevisited,Bell’sInequalities,andAnother ReturntoHiddenVariables(1957–1968) 1216 (c) TheAharonov–BohmE¤ect(1959–1963) 1222 3.3 Further Interpretationsand Experimental Confirmation of the Standard QuantumMechanics (1957–1999) 1224 (a) TheMany-WorldInterpretationandOtherProposals(1957–1973) 1224 (b) TestsofEPR-TypeGedankenexperiments:HiddenVariablesor Nonlocality(1972–1986) 1229 (c) TheProcessofDisentanglementofStatesandSchro¨dinger’sCat: AnExperimentalDemonstration(1981–1999) 1235 Conclusion: Four Generations of QuantumPhysicists 1244 References 1255 AuthorIndex 1441 Subject Index for Volumes 1to 6 1469 Chapter IV The Conceptual Completion and the Extensions of Quantum Mechanics (1932–1941) Introduction The invention of quantum and wave mechanics and the great, if not complete, progress achieved by these theories in describing atomic, molecular, solid-state and—to some extent—nuclear phenomena, established a domain of microphysics in addition to the previously existing macrophysics. To the latter domain of clas- sicaltheoriescreatedsincethe17thcenturyapplied—principally,themechanicsof Newton and his successors, and the electrodynamics of Maxwell, Hertz, Lorentz, and Einstein. The statistical mechanics of Maxwell, Boltzmann, Gibbs, Einstein, and others indicated a transition to microphysics; when applied to explain the behaviour of atomic and molecular ensembles, it exhibited serious limitations of theclassicalapproach.Classicaltheorieswerecloselyconnectedwithacontinuous description of matter and the local causality of physical processes. The micro- scopic phenomena exhibited discontinuities, ‘quantum’ features, which demanded changes fromthe classical description. In the standard scheme of quantum theory that emerged between 1926 and 1928, notably in Go¨ttingen, Cambridge, and Copenhagen,thefollowing descriptionarose: (i) Microscopicnaturalphenomenacouldbetreatedonthebasisofthetheoriesof matrix and wave mechanics, i.e., formally di¤erent but mathematically equiva- lentalgebraicandoperatorformulations. (ii) Thequantum-mechanicaltheoriessatisfiedtheknownconservationprinciplesof energy,momentum,angularmomentum,electricchargeandcurrent,etc. (iii) Thevisualizable(anschauliche)particleandwavepicturesoftheclassicaltheories had to be replaced by ‘dualistic’ or ‘complementary’ aspects of microscopic objectswhichexhibitedsimultaneousparticleandwavefeatures. (iv) The causal structure known from the classical laws—i.e., the di¤erential equa- tions—remained valid for the quantum-mechanical laws, but the behaviour of quantum-mechanicalobjectsdeviatedfromthoseofclassicalones. (v) BasedonBorn’sstatisticalinterpretationofthewavefunctionandHeisenberg’s uncertainty (or indeterminacy) relations, Bohr (on the physical side) and von Neumann (on the mathematical side) proposed a subtle formalism that ac- counted for the measurement of microscopic properties by macroscopic instru- ments (and observers), in which the classical subject–object relation introduced 300yearsearlierbyRene´ Descarteswasreplacedbyadi¤erentone. The completed physical theory of microscopic phenomena that thus arose,and wassooncharacterizedasthe‘Copenhageninterpretationofquantummechanics,’