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# The standard model of cosmology

DOI link for The standard model of cosmology

The standard model of cosmology book

# The standard model of cosmology

DOI link for The standard model of cosmology

The standard model of cosmology book

## ABSTRACT

The principal concern of this book is the way in which recent particle physics, including electroweak theory, quantum chromodynamics, grand unified theory, supersymmetry, supergravity and superstring theory, has changed our standpoint on the history of the universe when its temperature was greater than 10^{15} K. This will be studied in the context of the Friedman–Robertson–Walker solution of the Einstein equations of general relativity. In this chapter, therefore, our first task is the derivation of the field equations relating the scale factor R(t) that appears in the metric to the energy density ρ and the pressure p that characterize the (assumed homogeneous and isotropic) energy–momentum tensor. This is done in the following two sections. In section 1.4 we show how, for a given equation of state, energy–momentum conservation determines the scale dependence of the energy density and pressure. The standard solutions for the time dependence of the scale factor in a radiation-dominated universe, in a matter-dominated universe, and in a cosmological constant-dominated universe are presented in section 1.5; we give an estimate of the age of the universe in the matter-dominated case in section 1.6. In section 1.7, we present the evidence that there is, in fact, a nonzero cosmological constant and discuss why its size is so difficult to explain. The discussion of phase transitions and of relics that is given in later chapters also requires a description of the thermodynamics of the universe. So in the following two sections we describe the equilibrium thermodynamics of the expanding universe and derive the time dependence of the temperature in the various epochs. In section 1.10, we discuss briefly the ‘recombination’ of protons and electrons that left the presently observed cosmic microwave background radiation. Finally, the synthesis of the light elements that commenced towards the end of the first three minutes is discussed in section 1.11. The consistency of the predicted abundances with those inferred from the measured abundances determines the so-called baryon asymmetry of the universe, whose origin is discussed at length in chapter 4.