Introduction to cosmology Today results on dark energy Future experiments Search for dark energy

Introduction to cosmology(1) 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: The Hubble parameter (expansion rate) reads simply: w 0 =0 w 1 =0 w 0 =1/3 w 1 =0 w 0 =-1/3 w 1 =0 w 0 =? w 1 =? With Supernovae the Hubble parameter can be measure through the magnitude z=redshift Dark energy w 0 =-1 w 1 =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’inflation l’expansion expansion SNFactory (300 SNe) CFHTLS (700 SNe) Mesure de w a 10 % (limitation sol) SNAP (2000 SNe) mesure w à 0.02 et w 1 à 0.1 What can we expect for the future(SNLS/SNAP)

dataanalysisphysics 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 curve spectrographe 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 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

flat Stat 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

Weak Lensing + CMB Expected results for SNAP

Contrôle des systématiques et 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….