the physics of inflation and dark energy 1.3 dark energy: some evidence (short list) ages of glob....
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The physics of inflation and dark energy
1.3 Dark energy: some evidence (short list)
•Ages of glob. clusters/galaxies at z~2-3: m 0.6
•SN Ia: - m 0.3
•CMB: + m 1.0
•Large scale motions: 0.15 m 0.4
•Cluster mass function: m 0.3
Bottom line: many indep. hints that m 0.35
0.65
0.0)
The physics of inflation and dark energy 2. How to achieve acceleration
•Newtonian physics ?DENIED
...only mass is a source for gravity in Newtonian physics
•Einstein’s theory ?
APPROVED...energy density and pressure are components of a tensor (the stress-energy
tensor Tab) and both are sources for gravity
2.1 Physical basis
=> gravity is always attractive...
=> gravity can be “repulsive” (cosmologically) if pressure is sufficiently negative !
The physics of inflation and dark energy
2.2 Einstein, Friedman, de Sitter...
22
2
2222
1)( dr
Kr
drtadtdsFRW geometry:
a
a
abab TGG 8
jiji pTT
00
p<-/3: acceleration
p>-/3: decceleration
22
a
aH 23
8
a
KG
)3(3
4p
G
Friedman equations:
The physics of inflation and dark energy
2.3 Can pressure ever be negative?
0 v:Dust pc
31 :like-Vacuum p
31 v:Radiation pc
General equation of state: pX = wXXwXwX t
The physics of inflation and dark energy
2.4 Pressure and energy density conservation
dVpdE
dE )( Vd dVdV 0)(
dVpdV 0)(1
pdt
dV
Vdt
d
Energy conservation law in FRW: 0)(3
XXX pa
a
)(3 taV
0)w1(3
XXX a
a
wX constant:
)w1(3
00
X
a
aX
)w1(3
2
00
X
t
taa
If X is dominant:
wRad = 1/3wDust = 0w= -1wX = ...
The physics of inflation and dark energy
2.5 Life in an accelerating spacetime
s
00
t
taa
v = c
v = c
v = c
v = c
31- w 1s
:onAccelerati
Horizon:Rhorizon = H-1