Based on talks given at "Understanding our Universe at the close of the 20th century", Cargese, April 2000. (astro-ph/0009491)


ACCELERATION OF THE UNIVERSE

Andrew R. Liddle


Astronomy Centre, University of Sussex, Brighton BN1 9QJ, United Kingdom


Abstract. The cosmological model best capable of fitting current observational data features two separate epochs during which the Universe is accelerating. During the earliest stages of the Universe, such acceleration is known as cosmological inflation, believed to explain the global properties of the Universe and the origin of structure. Observations of the present state of the Universe strongly suggest that its density is currently dominated by dark energy with properties equivalent or similar to a cosmological constant. In these lecture notes, I provide an introductory account of both topics, including the possibility that the two epochs may share the same physical description, and give an overview of the current status.


Table of Contents

OVERVIEW

A HOT BIG BANG REMINDER
Overview
Equations of motion
Standard cosmological solutions
Critical density and the density parameter
Characteristic scales and horizons
Redshift and temperature
The history of the Universe

THE INFLATIONARY COSMOLOGY
The definition of inflation
Scalar fields and their potentials
Models of inflation
Equations of motion and solutions
The relation between inflation and slow-roll
The amount of inflation
A worked example: polynomial chaotic inflation
Multi-field theories
Reheating after inflation

DENSITY PERTURBATIONS AND GRAVITATIONAL WAVES
Production during inflation
A worked example
Observational consequences
Testing the idea of inflation
Growing mode perturbations
Gaussianity and adiabaticity
Tensor and vector modes
Power-law spectra

ACCELERATION IN THE PRESENT UNIVERSE
Cosmological constant: exact or effective?
Scaling solutions and trackers
Challenges for quintessence

SUMMARY

REFERENCES

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