Observing evolving Dark
Energy while Living in the
cold spot
Wessel Valkenburg, ITTK, RWTH Aachen
References:
WV, arXiv:1104.1082
Starobinsky, WV, in preparation
Outline
• How can structure mimic DE?
• The Cold Spot is there: what do we see
from its inside?
• GR solution the problem
• Effect on apparent w
l(z) / lFLRW(z)
Mimicking Λ
5
1
r/L
2
1
0
00
0.5 11 0 0 0.5
0.5 1 1
0.5
r/L
r/L
r/Lr/L
[Biswas, Notari, WV, 2009]
l(z) / lFLRW(z)
Mimicking Λ
5
1
r/L
2
1
0
00
0.5 11 0 0 0.5
0.5 1 1
0.5
r/L
r/L
r/Lr/L
[Biswas, Notari, WV, 2009]
The Cold Spot
The Cold Spot
The Cold Spot
• d (CMB) = 14 Gpc / radian (co-moving)
A
The Cold Spot
• d (CMB) = 14 Gpc / radian (co-moving)
• Diameter ~ 5
A
o
The Cold Spot
• d (CMB) = 14 Gpc / radian (co-moving)
• Diameter ~ 5
• 14 Gpc / rad x 5 ≈ 1.1 Gpc (co-moving)
A
o
o
The Cold Spot
• d (CMB) = 14 Gpc / radian (co-moving)
• Diameter ~ 5
• 14 Gpc / rad x 5 ≈ 1.1 Gpc (co-moving)
(adiabatic)
• Sachs-Wolfe:
A
o
o
The Cold Spot
• d (CMB) = 14 Gpc / radian (co-moving)
• Diameter ~ 5
• 14 Gpc / rad x 5 ≈ 1.1 Gpc (co-moving)
(adiabatic)
• Sachs-Wolfe:
• The Cold Spot is over-dense.
A
o
o
Lemaître-Tolman-Bondi
Each ‘isoradial shell’ obeys its own FLRW equation.
Einstein equations
Einstein equations
Einstein equations
Einstein equations
Solved!
[WV, arXiv:1104.1082]
And the spatial
derivative
[WV, arXiv:1104.1082]
bl / l (t0) = 0.4
bl / l (z=1089)
0.0004
0.0003
0.0002
0.0001
0
-0.0001
0
0.5
1
1.5
degrees
2
bl / l (t0) = 0.4
0
-20
6T (µK)
-40
-60
-80
-100
-120
-140
0
0.5
1
1.5
degrees
2
Make Mock SN based
on ΛCDM + Spot
Mock SN data
46
177.0 µK
RCDM
-152.6 µK
44
µ
42
45.3
40
45
38
44.7
36
34
1.3
0
0.5
1.4
1
1.5
z
1.5
2
2.5
Fit wΛCDM
1
1DE
0.9
0.8
0.7
0.6
0.5
-200 -150 -100 -50 0 50 100 150 200
6T (µK)
[Starobinsky, WV, in preparation]
Fit wΛCDM
-0.5
w
-1
-1.5
-2
-200 -150 -100 -50 0 50 100 150 200
6T (µK)
[Starobinsky, WV, in preparation]
Summary
Summary
• Large local void is ad-hoc
Summary
• Large local void is ad-hoc
• Living in the Cold Spot:
Summary
• Large local void is ad-hoc
• Living in the Cold Spot:
• Cold Spot is there: not so ad-hoc
Summary
• Large local void is ad-hoc
• Living in the Cold Spot:
• Cold Spot is there: not so ad-hoc
• w could be off by 10%
Summary
• Large local void is ad-hoc
• Living in the Cold Spot:
• Cold Spot is there: not so ad-hoc
• w could be off by 10%
• Developed exact spherical collapse in
ΛCDM on the way