Variation of Physical Constants  

In General > s.a. cosmology [future of the universe]; gravitational phenomenology; modified gravity.
* History: Predicted by a number of theories, such as Kaluza-Klein; 1912, Einstein worked on variable-c gravity; 1937, Dirac proposed that α could vary; 1955, Landau proposal; Bimetric theories predict a variation of c; 2009, Variations of constants of nature and acceleration of the universe could be related and governed by the evolution of a single field.
@ Reviews, status: Carilli pw(01)oct; Chiba gq/01-proc; Martins PTRS(02)ap; Uzan ap/04-proc; Olive & Qian PT(04)oct; Barrow & Webb SA(05)jun; Barrow PTRS(05)ap; news SFN(05)dec, space(06)jul; Dent AIP(07)hp/06; Flambaum IJMPA(07)-a0705; Melnikov G&C(07); Fritzsch NPPS(10); Peik NPPS(10); Berengut & Flambaum JPCS(11)-a1009; Chiba PTP(11)-a1111; Calmet & Keller a1410; Solà MPLA(15)-a1507; Levshakov a1603-proc [astrophysical methods]; Martins RPP(17)-a1709.
@ General references: Belinchón & Alfonso-Faus IJMPD(01)gq/04 [\(\hbar\)c = const]; Armendáriz-Picón PRD(02) [model]; Langacker IJMPA(04)hp/03-conf [and extra dimensions]; Buchalter ap/04 [c, G, h, cosmology]; Ignatiev & Carson PLA(04) [e, \(\hbar\), c: constraints]; MacGibbon ap/06, PRL(07)-a0706 [maximal rate allowed by second law of thermodynamics]; Flambaum AIP(06)phy; Martins ap/06-proc [and dark energy]; Shaw gq/07 [possible seasonal changes]; Nea RPP(07) [comparisons of atomic frequency standards]; Fritzsch MPLA(08); Uzan a0907-proc, LRR(11)-a1009 [general relativity extensions, cosmology]; Dent a1005-MG12; Levshakov et al ApJ(11)-a1106 [use of methanol lines as tracers]; Monteiro et al a1309-proc, Thompson a1602-MG14 [and fundamental physics].
@ Theory: Barrow gq/97-ln; Dzuba et al PRL(99)phy/98; Vilenkin PRL(98)ht; Barrow & O'Toole MNRAS(01)ap/99 [in space]; Duff ht/02; Uzan RMP(03)hp/02; Rich AJP(03)oct-phy/02 [consequences]; Barrow ASS(03)gq/02-proc; Vucetich AIP(03)ap/02 [models]; Marion et al PRL(03)phy/02, Fischer et al PRL(04)phy/03 [lab experiment]; Dent et al PRD(08)-a0808; Flambaum PRL(09)-a0808 [critique of black-hole bounds], reply MacGibbon PRL(09)-a0810; Dent et al PRD(09)-a0812 [comparison of bounds]; Damour SSR(09)-a0906-conf [and the equivalence principle]; Flambaum & Berengut IJMPA(09); Thompson MNRAS(12)-a1202 [in slow-roll quintessence]; Duff a1412; Fritzsch et al EPJC(17)-a1605 [in running vacuum models]; Hassan et al a1807 [from non-perturbative matter-gravity theories]; > s.a. early-universe nucleosynthesis.
@ And other physics: Gleiser & Taylor PRD(85), PRD(86) [and Kaluza-Klein theory]; Nunes et al a0910-proc [and cosmological acceleration]; Kozlov & Levshakov AdP(13)-a1304 [and molecular transitions]; Ivashchuk & Melnikov G&C(14)-a1401 [in 10D "Friedmann-Calabi-Yau" superstring cosmology]; Thompson Univ-a1702-proc [constraints on particle physics parameters].

Specific Constants > s.a. electron [mass]; fine-structure constant; variation of newton's gravitational constant.
* Variation of c: It can be produced in at least two different ways, a classical mechanism arising from the coupling of the electromagnetic field to other fields, and a quantum one arising from the interaction of photons with virtual charged-particle pairs in possibly different vacua.
* Variation of e/p mass ratio: Given that gluons, not quarks, make up most of the proton's mass, variations in μ = mp / me could arise if the strong nuclear force changes in time, as some theorists have speculated; 2015, No evidence of variation over a look-back time of 11.4 Gyr.
@ Variation of c: Dicke RMP(57) ['electromagnetic' theory of gravitation]; Tiwari in(80)gq/02; Ellman phy/98; Moffat ap/98-fs; Coule MPLA(99); Albrecht AIP(99)ap; Manida gq/99; Clayton & Moffat PLB(99)ap/98, PLB(00), PLB(01)gq/01 [bimetric]; Carlip PRD(03)gq/02 [and black-hole thermodynamics]; Magueijo 03, RPP(03)ap; Ellis & Uzan AJP(05)mar-gq/03; Bel gq/03; Jafari & Shariati IJMPD(04)gq/03 [as reformulations of special relativity];
Ellis GRG(07)ap [requirements on theories], comments Magueijo & Moffat GRG(08)-a0705; Iorio GRG(09)-a0901 [planetary tests]; Izadi & Shojai CQG(09) [in extended-gravity theories]; Qi et al PRD(14)-a1407; Coumbe a1509-MG14 [and dimensional reduction]; Salzano et al PRD(16)-a1511 [with future galaxy surveys]; > s.a. mach's principle; vacuum phenomenology.
@ Variation of c and G: Avelino & Martins PLB(99)ap [cosmology].
@ Variation of G and Λ: Sharif & Kausar JKPS(09)-a0911 [Bianchi III and Kantowski-Sachs cosmologies].
@ Varying-speed-of-light cosmology: Barrow PRD(99); Magueijo PRD(09)-a0807 [bimetric, primordial fluctuations]; Roshan et al PLB(09)-a0901 [solutions]; Afshordi & Magueijo PRD(16) + news csm(16)nov [bimetric, critical geometry and scalar perturbations].
@ e/p mass ratio: Barshay & Kreyerhoff ap/07 [and a small cosmological constant]; Dent EPJST(08)-a0802-ln; Avelino PRD(08) [and α]; Malec et al MNRAS(10)-a1001, in(09)-a1001 [optical molecular transitions]; Landau & Scóccola A&A(10)-a1002 [and α]; Landau et al APP(12)-a1010 [depending on the local value of the Weyl tensor]; van Weerdenburg et al PRL(11)-a1104; Bagdonaite et al ApJ(14)-a1308, PRL(13); Mohamadnejad MPLA(19)-a1806 [from variation of Higgs VEV with cosmic time].
@ Coupling constants: Chamoun et al PLB(01) [strong coupling constant]; Kostelecký et al PRD(03) [and Lorentz violation]; Shaw & Barrow PRD(05)gq/04 [electroweak, quantum corrections]; Bambi & Drago APP(08)-a0711 [bounds from GRBs]; Ferrero & Altschul PRD(10) [Fermi constant GF]; Ferreira & Martins PRD(15)-a1506 [stability].
@ QCD parameters: Dmitriev & Flambaum PRD(03)ap/02 [\(m^~_q/\Lambda^~_{\rm QCD}\)]; Beane & Savage NPA(03)hp/02 [\(m^~_q\) and nuclear physics]; Damour & Donoghue CQG(11)-a1104 [and lunar laser ranging]; Fischbach et al a1505-proc [indications of time-varying nuclear decay constants].
@ Planck's constant: Seshavatharam1 & Lakshminarayana IJA(13); Mangano et al IJMPA(15)-a1509 [theory]; de Gosson & Mohageg a1612 [dependence of quantum states on h]; de Gosson a1706 [consequences for transitions between pure and mixed quantum states].
@ Other constants: Bekenstein & Sagi PRD(08)-a0802 [\(G\) and Milgrom's \(a^~_0\) MOND parameter]; Scherrer a0903 [time variation of π :-)]; Milgrom PRD(15)-a1412 [MOND parameter].
> Various theories: see brane cosmology; cosmological constant; dark matter; FLRW models; gravitation ["variable lightcone"]; inflationary phenomenology; quantum cosmology; quantum geometrodynamics; relativistic cosmology; renormalization; types of gauge theories [with varying effective charge].

Bounds and Phenomenology > s.a. cosmic acceleration; modified lorentz symmetry; scalar-tensor gravity; spacetime singularities.
* c, status: 2002, P Davies et al say examination of black holes and thermodynamics suggests that \(\dot\alpha/\alpha\) is due to \(\dot c\).
* e/p mass ratio, status: 2006, Evidence from extreme UV lines of H for a 0.002% change over 12 Gyr, at the 3.5-σ level; 2007, Stronger upper bound of (−1 ± 3) × 10−16/yr [from the inversion spectrum of ammonia]; 2008, Upper bound (−3.8 ± 5.6) × 10−14/yr; 2009, Integrated Δμ/μ measured is (−7 ± 8) × 10−6; 2011, New bound (0.3 ± 3.2stat ± 1.9sys) × 10−6 from z = 2 to current time; 2013, Tighter bounds; 2014, \(\dot\mu/\mu\) = 0.2(1.1) × 10−6/yr.
@ General references: Sisterna & Vucetich PRD(90); Nordtvedt IJMPA(02)gq [and equivalence principle]; Olive et al PRD(02); Chengalur & Kanekar PRL(03)ap, Kanekar et al PRL(05) [using OH lines]; Rich AJP(03)oct-phy/02 [consequences]; Shaw & Barrow PRD(06)gq/05, PLB(06)gq/05, PRD(06)gq, Barrow & Shaw GRG(07)gq/06 [local effects]; Kanekar MPLA(08)-a0810 [techniques]; Landau et al PRD(08) [fine-structure constant, Higgs vacuum expectation value, electron mass]; Shaw & Barrow a1002-proc [constraints from seasonal variations]; Kanekar et al ApJ(10) + news ns(10)jun [from conjugate radio-wave absorption and emission lines in gas cloud spectrum]; Rellergert et al PRL(10); Curran et al A&A(11)-a1108; Kanekar et al ApJL(12)-a1201; Levshakov et al A&AL(12)-a1203; Rahmani et al MNRAS(12)-a1206 [using 21-cm absorbers]; Leite & Martins PRD(16)-a1607 [constraints on Bekenstein-type models]; Hart & Chluba MNRAS(18)-a1705; Amendola et al JCAP(18)-a1712 [Planck mass, from direct detection of gravitational waves]; Pašteka et al PRL(19) [monitoring the size of solids].
@ Spatial variation: Barrow PRD(05)ap [cosmological bounds]; Levshakov et al A&A(10)-a1004 [\(\alpha^2/(m_e/m_p)\) in the Milky Way galaxy]; Berengut et al PRD(11)-a1009; Iorio MNRAS(11)-a1104 [orbital effects].
@ Dependence on gravitational potential: Dent PRL(08) [Eötvös-type bounds]; Bagdonaite et al PRL(14)-a1409 [e/p mass ratio].
@ And nucleosynthesis: Ichikawa & Kawasaki PRD(02); MacDonald & Mullan PRD(09)-a0904 [strong force and anthropic principle]; Coc et al a1301-proc.
@ And inflation: Martins ap/00-conf; Chamoun et al IJMPD(07)ap/06 [strong coupling constant].
@ Planck's constant: Kentosh & Mohageg PRL(12)-a1203, comment Berengut & Flambaum PRL(12)-a1203 [from GPS clock-correction data]; Calmet PTRS(15)-a1504 [energy scale dependence, bounds]; Huang PRD(16)-a1511 [observational effects].
@ e/p mass ratio: Tzanavaris et al PRL(05)ap/04, MNRAS(07)ap/06 [21-cm + UV lines]; Barrow & Magueijo PRD(05)ap [cosmological constraints]; Ivanchik A&A(05)ap; Reinhold et al PRL(06) + pn(06)apr [evidence]; Chiba et al PRD(07); Flambaum & Kozlov PRL(07) + pw(07)jun; Shelkovnikov et al PRL(08) [lab constraint]; Murphy et al Sci(08)jun + sr(08)jun, King et al PRL(08)-a0807 [quasar spectra]; Thompson et al ApJ(09)-a0907 [consistent with no change over 11.5 Gyr]; Levshakov et al IAU-a0911; Beloy et al PRA(10) [diatomic molecules]; King PhD(11)-a1202 [quasar absorption lines]; King et al MNRAS(11)-a1106 [H2 transitions in quasar spectra]; Bagdonaite et al Sci(12)dec + news at(12)dec [ethanol torsional spectrum]; Levshakov et al a1307-proc; Wendt AN(14)-a1310 [based on H2 observations]; Huntemann et al PRL(14), Godun et al PRL(14) [atomic clock measurements]; Kanekar et al MNRAS(15)-a1412 [methanol lines]; Bagdonaite et al PRL(15); Daprà et al MNRAS(15)-a1509 [from H2 absorption]; Owens et al MNRAS(15) [from vibrations of hydronium, protonated water]; Ubachs et al RMP(16)-a1511 [with H2 quasar absorption method]; Ubachs SSR(18)-a1709-conf.
@ Variation of c: Albrecht & Magueijo PRD(99) [cosmology]; Bekenstein ap/03 [and lab spectroscopy].
> Related topics: see torsion and physical theories [constraints on f(T) gravity].

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