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# Early Universe Cosmology and Tests of Fundamental Physics:

Report of the P4.8 Working Subgroup, Snowmass 2001

### Andreas Albrecht ^{1}, Joshua A. Frieman ^{2, 3},
Mark Trodden ^{4}

^{1} Department of Physics

University of
California at Davis

One Shields Ave.

Davis, CA 95616
^{2} NASA/Fermilab Astrophysics Center

Fermi National
Accelerator Laboratory

P. O. Box 500, Batavia, IL 60510

^{3} Department of Astronomy & Astrophysics

The University of
Chicago

5640 S. Ellis Avenue, Chicago, IL 60637

^{4} Department of Physics

Syracuse University

Syracuse, NY, 13244-1130

**Abstract.**
This is the report of the *Working Group on Early Universe
Cosmology and Tests of Fundamental Physics*, group P4.8 of the of
the Snowmass 2001 conference. Here we summarize the impressive
array of advances that have taken place in this field, and
identify opportunities for even greater progress in the future.
Topics include Dark Energy, Cosmic Acceleration, Inflation, Phase
Transitions, Baryogenesis, and String/M-theory Cosmology. The
introductory section gives an executive summary with six key open
questions on which we can expect to make significant progress.

**Table of Contents**

- INTRODUCTION

- DARK MATTER

- DARK ENERGY AND THE ACCELERATING UNIVERSE

- Inflation: Models Tests and Alternatives
- Overview
- The basic idea
- Tests of Inflation
- Density
- Coherence from inflation
- Gravity waves from inflation
- The scalar spectral index
- Further tests of inflation
- Can one
* really* test inflation?

- Inflation and fundamental physics
- Alternatives to inflation

- PHASE TRANSITION AND THEIR RELICS
- Overview
- The many roles of cosmic phase transitions

- BARYOGENESIS

- FUNDAMENTAL PHYSICS AND COSMOLOGY
- Finite Temperature String / M-Theory and
Cosmology
- Extra Dimensions and Cosmology
- de-Sitter Space as a Solution to M-Theory
- Transplanckian Physics and Cosmology

- REFERENCES