Gauge Theory and the Early Universe

P. de Bernardis, S. Masi , G. Moreno Dipartimento di Fisica, Universita' "La Sapienza" 00184 Roma Italy ABSTRACT. Anisotropy measurement techniques and results are reviewed, with special attention given to experimental problems. The cosmological relevance of the dipole anisotropy, the only anisotropy truly detected in the Cosmic Background Radiation, is discussed. 1. INTRODUCTION Anisotropy of the Cosmic Background Radiation at 2.7 K (CBR hereafter) is a cosmological topic with a wide range of applications. In order to define anisotropy let us consider fig. 1 a, where the celestial sphere is shown with two beams A and B, with beamwidth 0 and angular separation e. We define the anisotropy of CBR at angular scale e in terms of the difference i'2,1 between the CBR flux I(ex,u) measured in the two beams. At small angular scales (el? a deterministic approach is preferred, and the CBR flux I(ex, S) is expressed as a sum of spherical harmonics (2) I (ex, S) = I ~ aIm Y (ex, S) lm I,m The alm coefficients give the dipole, quadrupole and higher order components of the anisotropy. 257 P. Galeotti and D. N. Schramm (eds.), Gauge Theory and the Early Universe, 257-282.

Gauge Theory and the Early Universe.- Toward the Inflationary Paradigm: Lectures on Inflationary Cosmology.- The Problem of Origin of the Primordial Cosmological Perturbations.- Galaxy Formation in Cold Dark Matter Dominated Universes: Observational Tests.- Phenomenology and Cosmology with Superstring Motivated Models.- Monopoles and Axions in an Inflationary Universe.- Cosmic Information and the “anthropic” Principle.- Trends in the Astrophysics of Light Elements: Cosmology and Stellar Physics.- The Consistency Problems of Large Scale Structure, Dark Matter, and Galaxy Formation.- Cosmolgy and Extra Dimensions.- Anisotropy Measurements of the Microwave Background.- Strange Matter in the Universe.- An Experimental Search for Galactic Axions.- R2 Inflation.- On the Effective Evolution Equation of the Scalar Field in the New Inflationary Universe.- Constrainta on the Geometry of the 5th Dimension in Cosmological Solutions of Five Dimensional Relativity in Vacuum.- Recent Developments in Quantum Cosmology.- A No-Hair Theorem for Inhomogeneous Cosmologies.- Constraints on Algebraically Extended Theories of Gravity.- On Kaluza-Klein Theories.- The Intergalactic Medium.- Relations Between Astronomical Parameters for the Universe with Cosmological Constant and Radiation Pressure.