# COSMOLOGY OF CHAMELEONS WITH POWER-LAW COUPLINGS

## Abstract

In chameleon field theories, a scalar field can couple to matter with gravitational strength and still evade local gravity constraints due to a combination of self-interactions and the couplings to matter. Originally, these theories were proposed with a constant coupling to matter; however, the chameleon mechanism also extends to the case where the coupling becomes field dependent. We study the cosmology of chameleon models with power-law couplings and power-law potentials. It is found that these generalized chameleons, when viable, have a background expansion very close to {Lambda}CDM, but can in some special cases enhance the growth of the linear perturbations at low redshifts. For the models we consider, it is found that this region of the parameter space is ruled out by local gravity constraints. Imposing a coupling to dark matter only, the local constraints are avoided, and it is possible to have observable signatures on the linear matter perturbations.

- Authors:

- Institute of Theoretical Astrophysics, University of Oslo, Box 1029, 0315 Oslo (Norway)

- Publication Date:

- OSTI Identifier:
- 21576823

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Astrophysical Journal; Journal Volume: 733; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/733/1/7

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGY; COUPLING; FIELD THEORIES; INTERACTIONS; NONLUMINOUS MATTER; MATTER

### Citation Formats

```
Mota, David F., and Winther, Hans A.
```*COSMOLOGY OF CHAMELEONS WITH POWER-LAW COUPLINGS*. United States: N. p., 2011.
Web. doi:10.1088/0004-637X/733/1/7.

```
Mota, David F., & Winther, Hans A.
```*COSMOLOGY OF CHAMELEONS WITH POWER-LAW COUPLINGS*. United States. doi:10.1088/0004-637X/733/1/7.

```
Mota, David F., and Winther, Hans A. Fri .
"COSMOLOGY OF CHAMELEONS WITH POWER-LAW COUPLINGS". United States. doi:10.1088/0004-637X/733/1/7.
```

```
@article{osti_21576823,
```

title = {COSMOLOGY OF CHAMELEONS WITH POWER-LAW COUPLINGS},

author = {Mota, David F. and Winther, Hans A.},

abstractNote = {In chameleon field theories, a scalar field can couple to matter with gravitational strength and still evade local gravity constraints due to a combination of self-interactions and the couplings to matter. Originally, these theories were proposed with a constant coupling to matter; however, the chameleon mechanism also extends to the case where the coupling becomes field dependent. We study the cosmology of chameleon models with power-law couplings and power-law potentials. It is found that these generalized chameleons, when viable, have a background expansion very close to {Lambda}CDM, but can in some special cases enhance the growth of the linear perturbations at low redshifts. For the models we consider, it is found that this region of the parameter space is ruled out by local gravity constraints. Imposing a coupling to dark matter only, the local constraints are avoided, and it is possible to have observable signatures on the linear matter perturbations.},

doi = {10.1088/0004-637X/733/1/7},

journal = {Astrophysical Journal},

number = 1,

volume = 733,

place = {United States},

year = {Fri May 20 00:00:00 EDT 2011},

month = {Fri May 20 00:00:00 EDT 2011}

}