# Anisotropic, nonsingular early universe model leading to a realistic cosmology

## Abstract

We present a novel cosmological model in which scalar field matter in a biaxial Bianchi IX geometry leads to a nonsingular 'pancaking' solution: the hypersurface volume goes to zero instantaneously at the 'big bang', but all physical quantities, such as curvature invariants and the matter energy density remain finite, and continue smoothly through the big bang. We demonstrate that there exist geodesics extending through the big bang, but that there are also incomplete geodesics that spiral infinitely around a topologically closed spatial dimension at the big bang, rendering it, at worst, a quasiregular singularity. The model is thus reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasiregular singularity; the two models are, however, rather different, as we will show in a future work. Here we concentrate on the cosmological implications of our model and show how the scalar field drives both isotropization and inflation, thus raising the question of whether structure on the largest scales was laid down at a time when the universe was still oblate (as also suggested by [T. S. Pereira, C. Pitrou, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 9 (2007)more »

- Authors:

- Astrophysics Group, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, CB3 0HE (United Kingdom)

- Publication Date:

- OSTI Identifier:
- 21260001

- Resource Type:
- Journal Article

- Journal Name:
- Physical Review. D, Particles Fields

- Additional Journal Information:
- Journal Volume: 79; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevD.79.043524; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0556-2821

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANISOTROPY; COSMOLOGICAL MODELS; COSMOLOGY; DISTURBANCES; ENERGY DENSITY; GEODESICS; INFLATION; MATHEMATICAL SOLUTIONS; PERTURBATION THEORY; SCALAR FIELDS; SIMULATION; SINGULARITY; STABILITY; UNIVERSE

### Citation Formats

```
Dechant, Pierre-Philippe, Lasenby, Anthony N., and Hobson, Michael P.
```*Anisotropic, nonsingular early universe model leading to a realistic cosmology*. United States: N. p., 2009.
Web. doi:10.1103/PHYSREVD.79.043524.

```
Dechant, Pierre-Philippe, Lasenby, Anthony N., & Hobson, Michael P.
```*Anisotropic, nonsingular early universe model leading to a realistic cosmology*. United States. doi:10.1103/PHYSREVD.79.043524.

```
Dechant, Pierre-Philippe, Lasenby, Anthony N., and Hobson, Michael P. Sun .
"Anisotropic, nonsingular early universe model leading to a realistic cosmology". United States. doi:10.1103/PHYSREVD.79.043524.
```

```
@article{osti_21260001,
```

title = {Anisotropic, nonsingular early universe model leading to a realistic cosmology},

author = {Dechant, Pierre-Philippe and Lasenby, Anthony N. and Hobson, Michael P.},

abstractNote = {We present a novel cosmological model in which scalar field matter in a biaxial Bianchi IX geometry leads to a nonsingular 'pancaking' solution: the hypersurface volume goes to zero instantaneously at the 'big bang', but all physical quantities, such as curvature invariants and the matter energy density remain finite, and continue smoothly through the big bang. We demonstrate that there exist geodesics extending through the big bang, but that there are also incomplete geodesics that spiral infinitely around a topologically closed spatial dimension at the big bang, rendering it, at worst, a quasiregular singularity. The model is thus reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasiregular singularity; the two models are, however, rather different, as we will show in a future work. Here we concentrate on the cosmological implications of our model and show how the scalar field drives both isotropization and inflation, thus raising the question of whether structure on the largest scales was laid down at a time when the universe was still oblate (as also suggested by [T. S. Pereira, C. Pitrou, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 9 (2007) 6.][C. Pitrou, T. S. Pereira, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 4 (2008) 4.][A. Guemruekcueoglu, C. Contaldi, and M. Peloso, J. Cosmol. Astropart. Phys. 11 (2007) 005.]). We also discuss the stability of our model to small perturbations around biaxiality and draw an analogy with cosmological perturbations. We conclude by presenting a separate, bouncing solution, which generalizes the known bouncing solution in closed FRW universes.},

doi = {10.1103/PHYSREVD.79.043524},

journal = {Physical Review. D, Particles Fields},

issn = {0556-2821},

number = 4,

volume = 79,

place = {United States},

year = {2009},

month = {2}

}