the dark side of gravity and our universe
DESCRIPTION
The Dark Side of Gravity and our Universe. Frédéric Henry-Couannier CPPM/RENOIR Marseille www.darksideofgravity.com. Motivations for alternative theories of gravity. Anomalous gravity effects?: Pioneer effect Anisotropies in CMB quadrupôle - PowerPoint PPT PresentationTRANSCRIPT
Frédéric Henry-Couannier
CPPM/RENOIR Marseille
www.darksideofgravity.com
The Dark Side of Gravity and our Universe
Motivations for alternativetheories of gravity
Anomalous gravity effects?:
Pioneer effect
Anisotropies in CMB quadrupôle
Cosmology ?=? GR+ Dark matter + Inflation + Dark energy + … ?!?!
Local PN gravity tests dont tell us that GR is right in the cosmological domain !
From non gravitational theory to GR
1. Requirement: equations should be invariant under general coordinate transformations
2. Covariantisation program: new field g(and derivatives)
3. gis not only a pseudoforce but describes a genuine interaction: gravity
1. & 2. &3. & simplicity GR: satisfies by construction the equivalence principle.
GR: a geometric theory ?1. GR equations: atoms&photons interact with g
field gravity affects the measured space and time intervals.
2. ghas the properties of a metric
The Geometrical viewpoint:
1.+2. gis the metric of space-time. The geometrical properties of gtell us about the geometry of space-time (Deformations, Curvature) Trajectories = geodesics
The non geometrical viewpoint
gis just a field, spacetime is a flat and static manifold with true metric . many possibilities:
1. Keep GR: the covariant theory of g
is not observable (not in the equations!)
2. « Multimetric » theories : 1. Introduce two or more independent gtype fields (Petit, Linde,
Damour…)
2. Introduce in equations: (Rosen)
3. Introducethrough g gis a Janus field: Respect the symetry between the two faces Dark Gravity (mimics
class 1.)
DG: Gravity with its Dark side
DG mimics bigravity theories: Our side Srandard Model lives in
gravity Other side Standard Model lives in
gravity is dark from our side viewpoint
Two gravities are related
anti-gravitational connection between 2 worlds
g
g
DG rehabilitates global space-time symmetries
Spacetime is flat as in QFT with metric we recover
Global Lorentz-Poincaré invariance Noether currents Global space-time discrete symmetries and Lorentz group
« bad » representations (negative energies, tachyons…)
DG cosmological solution satisfies
Two faces of our universe are conjugate under time reversal !
( ) ( ) ( )T
g t g t g t
DG equations
T
New equations
RG RGS S Extremum action
& eliminate
g
Global space-time symmetries freeze degrees of freedom
‘Isotropic form:’
Symmetry between space and time (links tachyons to bradions) 2 theories:
and
B A1/B A
1
1
1
1
1
1, ,
1
1
B B
A Ag g
A A
A A
Cosmology
GW
Gravity
Pioneer effect
Local gravity
As in Petit theory:
Objects living in the same gravity attract each other Objects living in different gravity reppel each other
2 22 /
2
2 2 3 32 /
00 2 3
( ) 1 2 2
1 4( ) 1 2 2
3
MG rii
MG r
MG M Gg r A e
r r
MG M G M Gg r e
A r r r
DG: RG:
Schwarschild Gravity
4 2 2
2
2
2 2 3 3
00 2 2 3
3( ) 1 1 2
2 2
132( ) 1 2 22
12
ii
MG MG M Gg r
r r r
MGMG M G M Grg rr r rMG
r
Cosmology in DG
CosmologyNo source term (exact compensation) symmetries completely determine the universes global gravity : Spatially flat universesNo Big Bang singularity in conformal cooOne universe is now constantly
accelerated in comoving coordinates Negligible expansion rate in early universeOur universe is twice older than in SM
Universe A(t)(dt2-d2)
GR:
Reversing time
=
Going backward in time
Time reversal
Dark gravity:
Reversing time
=
Jumping into hidden face of universe
1
A(t)~ t -2
A-1(t)
t=0: Big Bang
t → + ∞
t → + ∞- ∞←t
A(t)~e-t
Universe A(t)(dt2-d2)
Magnitude vs redshiftSNA test (SCP 2003)
Fit a(t) t∝
= 1.6±0.3(stat)
OK with constant acceleration
=2
From the CMB to large scale structures
Universe expansion rate negligible relative to fluctuations growing rate
Baryonic matter only, same density as in SM
Exponentially growing fluctuations early reach the nonlinear regime
No need for Dark Matter ?
Universe twice older: 26 billion years
Oldest galaxies (z=5): 17 billion years
Repelling gravity each galaxy creates a void in conjugate universe equivalent to a Halo
Other predictions of DG
Longitudinal spin0 gravitational waves
Different Schwarzschild solution (different PPN parameters, no BH)
Pioneer effect (postdiction)
Possibly new frame-dragging effects
Gravitational discontinuity effects
Conclusion
DG is essentially the other option of a binary choice at the level of the conceptual fondations of GR
DG has no coincidence problem, no epicyclesDG is a stable theory with repelling gravity DG is OK with all local tests of gravity and explains the Pioneer anomalyDG provides a promissing framework to compete with the cosmological SM but DG needs detailed simulations to see if it can actually compete with (do better than SM?).
RG vs DGThe metric is the object one must use to raise andlower indices on any tensor field
RG: is the metric
RG is the theory of
DG: is the metric
DG is the theory of non independent and
g
1g g g g g
1g g g g g
g
g g
La symétrie x/t
Forme la plus générale de
If , C viole la symétrie x/t
2 2 21d C Adx dt
A
2 2 21 1d dx Adt
C A
2 2 21 d Adx dt
A
A i
g
La symétrie x/t (II)
Si A=i:
Symétrie x/t OK
2 2 2d C dx dt
2 2 21d dx dt
C
2 2 2ˆd C dt dx
2 2 21ˆd dt dx
C
2 2 2 ˆ,d C dx dt g g
Discontinuities in gravity ?
Discontinuity could have trapped 3.106 solar masses < 0
in twin universe:
mimics a central BH
Conjugate universe void dominates: idem dark
matter HaloMatter dominates r
v
?A star