J. Garriga

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PAU training lectures on dark energy

• J. Garriga
• (U. Barcelona)

IFT, Madrid, December 2007
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(No Transcript)
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• Atoms
• Visible 1
• Invisible 3
• Photons 0.001
• Neutrinos lt1

Constrained by BBN
4 ordinary matter 96 unknown origin
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Decoupling
Cosmic acceleration
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Plan
1- Observational probes
Rulers and candles
Supernovae
CMB
Baryon acoustic oscillations in LSS
ISW-LSS cross-correlation
2- Theoretical musings
3- Dynamical dark energy
4- Infrared modifications of gravity
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Rulers and candles
Evolution of the scale factor is
tested by means of
Standard candles (e.g. supernovae)
LUMINOSITY DISTANCE
Standard rulers (e.g. something whose absolute
size is known)
ANGULAR DIAMETER DISTANCE
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1.a- rulers and candles
LOOKING OUT IN SPACE MEANS LOOKING BACK IN TIME
Proper time
Past light cone (this layer is all we see)
Proper size
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1.a- rulers and candles
INSTEAD OF TIME, WE USE REDSHIFT
Proper time
Proper length of the circle
Proper size
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1.a- rulers and candles
INSTEAD OF TIME, WE USE REDSHIFT
Proper time
Proper length of the circle
Proper size
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1.a- rulers and candles
INSTEAD OF TIME, WE USE REDSHIFT
Proper time
Proper size
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1.a- rulers and candles
INSTEAD OF TIME, WE USE REDSHIFT
Proper time
LUMINOSITY DISTANCE CONTAINS THE SAME
INFORMATION
Proper size
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Supernovae
Perlmutter et al, Riess et al 98
DECELERATION PARAMETER
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1.b- supernovae
Riess et al 2006 gold sample
In General Relativity
dark energy
Deceleartion parameter
(GongWang, 07)
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General Relativity
Well tested at solar system scale.
Homogeneity and isotropy
Gravity is attractive
there is DE, with
(causing a repulsive force)
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1.b- supernovae
Why is acceleration important at late time ?
(Friedmann equation)
for constant
Energy conservation
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Matter DM
Radiation
DE
Now
Big Bang
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1.b- supernovae
Riess et al 2006 gold sample
Astier et al 2005 SNLS 1st Yr
dark energy
Deceleartion parameter
(GongWang, 07)
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1.b- supernovae
gold sample
SNLS
(Alam et al 06)
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CMB
WMAP (Spergel et al. 2007)
Standard ruler at
SHIFT PARAMETER
(Wangmukherjee 06)
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Baryon acoustic oscillations
Eisenstein et al. 2005
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Courtesy of Wayne Hu
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1.d- Baryon acoustic oscillations
Two point correlation
Standard ruler at
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1.d- Baryon acoustic oscillations
Two point correlation
dr (c/H)dz
dr dAdq
Standard ruler at
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1.d- Baryon acoustic oscillations
Different models which fit the CMB equally well,
do not necessarily fit the baryon acoustic
oscillations
Evidence for dark energy even if SN and HST
ignored !
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SN BAO
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CONCORDANCE SN LSS CMB (vanilla w -1
)
WMAP vs. LSS
WMAP vs SN
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CONSTRAINTS ON A CONSTANT EQUATION OF STATE
PARAMETER w
Seems to be pretty close to a cosmological
constant !
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Need some parametrization
Alam, Sahni, Starobinsky 06
SNLS
Gold sample
GoldBAO CMB
BAO CMB
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A somewhat different parametrization of w(z)
GoldBAO CMB
GongWang 07
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ISW effect
The influence of dark energy on the cosmic
expansion slows the growth of inhomogeneities in
the dark matter and baryons.
This leads to the Integrated Sachs-Wolfe effect
in the CMB
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ISW leads to cross-correlation between CMB and LSS
This has been observed by several groups, and
leads to independent verification of
the existence of DE
(Pietrobon et al 2006)
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Where do we stand?
The case for dark energy is pretty strong
But what is it?
works remarkably well with very few parameters
Improved accuracy may show deviations
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Where do we stand?
The case for dark energy is pretty strong
But what is it?
works remarkably well with very few parameters
Improved accuracy may show deviations
-Improved H(z) diagrams

• Tests of structure growth history
• (gravitational lensing, cluster abundances,
• cross correlation of lensing and velocity fields)