Equivalence
Principle| Equivalence
Principle |
In General, Versions > s.a. quantum
equivalence principle; variation
of constants.
* History: Heuristic
principle introduced by Einstein in 1907 as a primary motivation for general
relativity.
* Weak (idea): Gravity is like an inertial force, in that it affects
the linear motion of all (small) objects equally.
$ Weak (Galileo): All pointlike bodies fall in the same way in a (possibly
strong) gravitational field; mi 
mg – mass.
$ Weak (Newton): For (possibly extended) slowly moving bodies in weak
fields, mi mg – composition/form.
* Relationships: When all assumptions are satisfied, the two above
versions are equivalent.
$ Modern versions: The only long-range field with gravitational-strength
couplings to matter is a massless spin-2 field, the graviton; The PPN 
parameter is the same for all types of matter.
* And general relativity:
The wep is built into the theory.
* Remark: This principle
concerns the passive gravitational mass mpass,
but mact must be equal to mpass in
order for momentum to be conserved and Newton's third law to be valid, so an
exterior gravitational field
is independent of what type of matter produces it; This is more
than
just a statement on gravitational effects felt by matter.
* Strong (idea): All (small) objects are equally affected by gravity
in every respect; A stationary observer in a gravitational potential V is
indistinguishable
from one moving with acceleration –
V and no gravitational
field; All
gravitational effects can be locally transformed away and no local
measurement can detect a gravitational field; Requires that matter
be coupled to gravity only through gab and 
abc,
not the curvature.
* And general relativity:
It is not built in, and there are situations where it is not satisfied.
@ Strong version: Bertotti & Grishchuk CQG(90);
in Ohanian & Ruffini 94
[good];
Aldrovandi
et al FP(03)gq/02 [with
torsion].
Violations > s.a. Chameleon
Field; tests of the equivalence principle; modified
lorentz symmetry.
* Of wep: May occur if
there are s = 0 and 1 particles with gravitational
strength couplings [@ Maddox Nat(91)mar], such as those predicted
by some unified theories like string theory; The best known consequences are
variation
of "constants'', non-universality of free fall, and relative drift
of atomic
clocks; May also induce 
oscillations
without the need for a
mass (& P Halprin).
* Of sep: There are at
least two local effects (using infinitesimal-size objects) that can detect
gravitational fields, the tidal distorsion of an object,
and the precession of a spinning non-spherical gyroscope;
A gravitational
field implies an unambiguous, nonzero Rabcd;
The strong equivalence principle fails even in Newtonian gravity; Violated
in QED in curved
spacetime, with "faster than light" photons (> see causality
violations),
and by metric-affine theories that predict vacuum birefringence (> see phenomenology).
@ Of wep: Will PRL(89)
[in non-symmetric gravity]; Göklü & Lämmerzahl CQG(08)-a0801 [from
metric fluctuations].
@ From string dilaton: Damour gq/97-in, gq/97-in;
[Landau et al ap/03-wd].
@ Other situations: Ellis gq/03 [leptons];
Ellis et al IJMPA(04)gq/03 [from
spacetime foam];
Barrow & Scherrer
PRD(04)ap [fermions
vs bosons]; Hehl & Obukhov GRG(08)-a0705 [and
electromagnetic coupling, axion and dilaton]; Bertolami et al PLB(07),
Le Delliou et al AIP(07)-a0709
[dark energy–dark matter
interaction in A586]; Carroll et al PRL(09)-a0807 [dark-matter-induced];
Hui et al PRD-a0905 [cosmological,
from modified gravity].
References
@ General: in Dicke 64; Klein Sci(71)jan;
Rabinowitz IEEE(90)phy/07 [falling
bodies, history]; Hughes CP(93);
Iliev JGP(98)gq;
Camacho MPLA(99)gq [continuous
quantum measurement]; Rohrlich FP(00)
[critique]; Damour CRAS-gq/01
[rev]; Ghins & Budden SHPMP(01);
Nordtvedt gq/02 [special
relativistic]; Drake AJP(06)jan
[and special / general relativity transition]; Schücking & Surowitz gq/07 [Einstein
1907]; Fabbri a0905 [and the geometrization of gravity].
@ Geometric formulation: Coleman & Schmidt JMP(95); Iliev JPA(96)gq,
JPA(97)gq;
Wesson GRG(03) [5D, weak]; Iliev gq/06-in
[and geodesic deviation].
@ Criticisms: Logunov et al SPU(96); Ginzburg & Froshenko SPU(95),
SPU(96) [reply].
@ In other theories:
Olmo PRL(07)gq/06 [in f(R)
gravity theories]; Kraiselburd & Vucetich a0902 [Bekenstein's
theory]; > s.a. kaluza-klein
phenomenology, theories of gravitation ["ultra-strong" version].
@ For Casimir energy:
Fulling et al PRD(07)ht;
Milton et al JPA(07)-a0705,
JPA(08)-a0710-in,
a0810-in; Shajesh
et al JPA(08)-a0711-in.
@ Generalized: Lyre IJMPD(00)gq [for
gauge charges]; Chiao gq/02/PRL
[extended, and Kramers-Kronig relations]; Mensky PLA(04)
[from energy-momentum conservation]; Wiltshire PRD(08)-a0809 [cosmological].
@ Related topics: 't Hooft JGP(84)
[and black-hole radiation]; Kreinovich & Zapatrin gq/97 [operational];
Carlip AJP(98)may-gq/99 [and
kinetic energy]; Özer gq/99 [and
electromagnetism];
Rohrlich PRD(01)
[despite self-interaction]; Rodrigues & Sharif FP(01)mp/03 [and
local Lorentz invariance]; Maluf et al CQG(07)-a0704
[tetrads and energy in freely
falling frames].
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