Measurements of Cosmological Parameters Amedeo Balbi Dipartimento di Fisica & INFN Università di Roma “Tor Vergata”

Background Cosmology Expanding universe, described by Friedmann equation:

Perturbations & Inflation Inflation generates perturbations through amplification of quantum fluctuations. In the basic picture, they obey Gaussian statistics, with a Harrison-Zel’dovich power spectrum:

Parameters from the CMB

CMB Anisotropy

CMB Power Spectrum Bennet et al. 2003

Total Density The typical angular size of fluctuations on the CMB depends on the global geometry of the Universe ( 1st peak position) The universe is flat

Hubble Constant HST Key Project: use Cepheids to calibrate distance indicators (z~0) Combining X-ray flux and SZ effect in clusters of galaxies (z~0.5) CMB: conformal distance to the decoupling surface (z~1000) Spergel et al. 2003

Cosmic Ages Spergel et al. 2003

Baryon Abundance CMB, ratio of acoustic peaks amplitude (Spergel et al. 2003): Primordial abundance of deuterium + BBN (Fields & Sarkar, 2004):

Primordial Abundances Fields & Sarkar, 2004

Matter Density Power spectrum from redshift surveys (e.g., 2dF, SDSS): Clusters of galaxies (e.g., Chandra):

Something Missing!

Type Ia Supernovae

Cosmic Concordance 1 (CMB) 1/3 (LSS) 2/3 (SN)

Amplitude of fluctuations Spergel et al. 2003

Inflation Universe is flat Primordial perturbations are adiabatic, Gaussian and scale-invariant (spectral index near unity) Gravitational wave background (tensor modes) is negligible No viable alternative makes all these predictions

Problems with Lambda Vacuum fluctuations in QFT: “Why now?”:

Dark Energy? Ideal fluid with generic equation of state: E.g., scalar field:

Constraints on Dark Energy Seljak et al. 2004

Precision Cosmology