•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….