Article
Physics of Cosmic Microwave Background anisotropies and primordial fluctuations
DURRER, Ruth
Abstract
The physics of the origin and evolution of CMB anisotropies is described. I explain the idea and status of cosmic parameter estimation and follow it up with critical comments on its dependence on model assumptions and initial conditions.
Reference
DURRER, Ruth. Physics of Cosmic Microwave Background anisotropies and primordial fluctuations. Space Science Reviews, 2002, vol. 100, no. 1-4, p. 3-14
DOI : 10.1023/A:1015822607090
Available at: http://archive-ouverte.unige.ch/unige:1001
Disclaimer: layout of this document may differ from the published version.
1 / 1 PHYSICS OF COSMIC MICROWAVE BACKGROUND ANISOTROPIES AND PRIMORDIAL FLUCTUATIONS
RUTH DURRER ([email protected]) Département de Physique Théorique, Université de Genève, Quai E. Anserment24, CH-1211 Genève, Switzerland
Received: ; Accepted in final form:
Abstract. The physics of the origin and evolution of CMB anisotropies is described, followed by a critical discussion of the present status of cosmic parameter estimation with CMB anisotropies.
Keywords: Cosmic microwave background anisotropies, cosmological parameters, primordial fluc- tuations, initial conditions, models
1. Introduction
The discovery of anisotropies in the cosmic microwave background (CMB) by the COBE satellitein 1992 (Smoot et al., 1992; Bennett et al., 1996) has stimulatedan enormous activity in this field which has culminated recently with the high preci- sion data of the BOOMERanG, MAXIMA-I and DASI experiments (de Bernardis et al., 2000;Hanany et al., 2000 ; Netterfield et al.,2001;Lee et al., 2001 ; Halver- son et al., 2001 ). The CMB is developing into the most important observational tool to study the early Universe. Recently, CMB data has been used mainly to determine cosmological parameters for a fixed model of initial fluctuations, namely scale invariant adiabatic perturbations. In my talk I outline this procedure and present some results. I will also mention the problem of degeneracies and indi- cate how these are removed by measurements of the CMB polarization or other cosmological data. Finally, I include a critical discussion of the model assumptions which enter the parameter estimations and will show in an example what happens it these assumptions are relaxed. In the next section we discuss in some detail the physics of the CMB. Then we investigate how CMB anisotropies depend on cosmological parameters. We also discuss degeneracies. In Section 4 we investigate the model dependence of the ’parameter estimation’ procedure. We end with some conclusions.
2. The physics of the CMB
Before discussing the possibilities and problems of parameter estimation using CMB anisotropydata I want to describe the physicsof these anisotropies. As CMB
Space Science Reviews 00: 1–12, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands. 2 RUTH DURRER anisotropies are small, they can be treated nearly completely within linear cosmo- logical perturbation theory. Effects due to non-linear clustering of matter, like e.g.
the Rees-Sciama effect, the Sunyaev-Zel’dovich effect or lensing are relevant only
> ` on very small angular scales ( 1000) and are not discussed here. Since the CMB anisotropies are a function on a sphere, they can be expanded
in spherical harmonics, `
∆T ∞ m=