Published in Physics Reports Journal-ref: Phys.Rept. 402 (2004) 267-406.
astro-ph/0407207

For a PDF version of the article, click here.

DARK MATTER AND BACKGROUND LIGHT

J.M. Overduin a and P.S. Wesson b


a Gravity Probe B, Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, U.S.A. 94305-4085
overduin@relgyro.stanford.edu
b Department of Physics, University of Waterloo, Ontario, Canada N2L 3G1
wesson@astro.uwaterloo.ca


Abstract. Progress in observational cosmology over the past five years has established that the Universe is dominated dynamically by dark matter and dark energy. Both these new and apparently independent forms of matter-energy have properties that are inconsistent with anything in the existing standard model of particle physics, and it appears that the latter must be extended. We review what is known about dark matter and energy from their impact on the light of the night sky. Most of the candidates that have been proposed so far are not perfectly black, but decay into or otherwise interact with photons in characteristic ways that can be accurately modelled and compared with observational data. We show how experimental limits on the intensity of cosmic background radiation in the microwave, infrared, optical, ultraviolet, x-ray and gamma-ray bands put strong limits on decaying vacuum energy, light axions, neutrinos, unstable weakly-interacting massive particles (WIMPs) and objects like black holes. Our conclusion is that the dark matter is most likely to be WIMPs if conventional cosmology holds; or higher-dimensional sources if spacetime needs to be extended.


Table of Contents

INTRODUCTION: THE LIGHT OF THE NIGHT SKY

THE INTENSITY OF COSMIC BACKGROUND RADIATION
Bolometric intensity
Characteristic values
Matter, energy and expansion
Olbers' paradox
Flat single-component models
Curved and multi-component models
A look ahead

THE SPECTRUM OF COSMIC BACKGROUND RADIATION
Spectral intensity
Comoving luminosity density
The delta-function spectrum
The Gaussian spectrum
The Planckian spectrum
Normal and starburst galaxies
Comparison with observation
Spectral resolution of Olbers' paradox

DARK MATTER AND DARK ENERGY
The four elements of modern cosmology
Baryonic dark matter
Cold dark matter
Massive neutrinos
Dark energy
Cosmological concordance
The coincidental Universe

DARK ENERGY
The variable cosmological "constant"
Models based on scalar fields
Theoretical and observational challenges
A phenomenological model
Energy density
Source luminosity
Bolometric intensity
Spectral energy distribution
The microwave background

AXIONS
"Invisible" axions
The multi-eV window
Axion halos
Bolometric intensity
The infrared and optical backgrounds

NEUTRINOS
The decaying-neutrino hypothesis
Neutrino halos
Halo luminosity
Free-streaming neutrinos
Extinction by gas and dust
The ultraviolet background

WEAKLY INTERACTING MASSIVE PARTICLES
The lightest supersymmetric particle
Pair annihilation
One-loop decays
Tree-level decays
Gravitinos
The x-ray and gamma-ray backgrounds

BLACK HOLES AND SOLITONS
Primordial black holes
Evolution and density
Spectral energy distribution
Bolometric intensity
Spectral intensity
Solitons

CONCLUSIONS

REFERENCES

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