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•Introduction to cosmology
•Today results on dark energy
•Future experiments
Search for dark energy
Introduction to cosmology(1)
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Univers is described by general relativity:
Geometry of Universe is fully described by its energy content:
Critical total energy density for which Universe is spatially flat
Matter relative energy density
Radiation relative energy density
Total relative energy density
Cosmological constant or vacuum relative energy density
Introduction to cosmology(2)
Each cosmological fluid is characterized by a state equation:
zwwp
zwX
XX .)( 10
)1(334320
101 )1()1()1()1()( wwzwXrmk zezzzHzH
The Hubble parameter (expansion rate) reads simply:
w0=0
w1=0
w0=1/3
w1=0
w0=-1/3
w1=0
w0=?
w1=?
))(( )1
,0
,,,,(
0
log*5.2 wXmkz wF
FHDfm L
With Supernovae the Hubble parameter can be measure through the magnitude
z=redshift
Dark energyw0=-1
w1=0
The last SN1a result: Vacuum density energy non zero
2002: clusters
2003: WMAP
2003 :SCP+ 11 SNIa HST
1999: SCP/ High z
Today status:The concordance model
SNAP
Après l’inflationl’expansion
expa
nsio
n
SNFactory (300 SNe)
CFHTLS (700 SNe)
Mesure de w a 10 % (limitation sol)
SNAP (2000 SNe) mesure w à 0.02 et w1 à 0.1
What can we expect for the future(SNLS/SNAP)
data analysis physics
The SN method
Images
Spectra
+ identification.
Ia
magnitude z(redshift)
galaxy
Hubble
SN1a=Are considered as standard candle
With which instrument ?
SNAP 2014: USA/French coll.
shutter
Focal plane
Spectrograph
electronics
Focal plane: Light curvespectrographe
0.61 Gigapixel
•36 CCD’s 10.5 m 3.5 x 3.5k ( 0.34 sq. deg.)
•36 HgCdTe’s 18 m l 2k x 2k ( 0.34 sq. deg.)
Sky scanSky scan
Spectrograph
x
y
Cutting out on the
slices
x
y
Re-arrangement
dispersion
Pixelised image in 3 dimensions
-Whole light conservd-no slit to position - very stable stable-easy to calibrate=> adapted for space
SNAP original spectrograph
Expected SNAP results for SN
flatStat seule
68 %
Simulation cppm
Comparative results
Weak Lensing by Large-Scale Structure
Distortion Matrix:
Direct measure of the distribution of Dark Matter in the universe
jij
iij zgdz
2
)(
Weak Lensing + CMB
Expected results for SNAP
Contrôle des systématiqueset des dégénérescences
Combiner avec d’autres méthodes•cisaillement gravitationnel (WL)•CMB
In number…
hypothèse
Summary
•New questions are now opened:
Can we believe that 70% of Universe energy is unknown ?
What is the nature of dark energy ?
•Ground experiment will probably give a confirmation of the first point
•But only a space telescope will be able to gives answer about the nature of dark energy.
•Otherwise, if CMB/WL/SN do not agree, it will mean that something is wrong in our understanding of cosmology or general relativity….