# Dark matter relics and the expansion rate in scalar-tensor theories

## Abstract

We study the impact of a modified expansion rate on the dark matter relic abundance in a class of scalar-tensor theories. The scalar-tensor theories we consider are motivated from string theory constructions, which have conformal as well as disformally coupled matter to the scalar. We investigate the effects of such a conformal coupling to the dark matter relic abundance for a wide range of initial conditions, masses and cross-sections. We find that exploiting all possible initial conditions, the annihilation cross-section required to satisfy the dark matter content can differ from the thermal average cross-section in the standard case. We also study the expansion rate in the disformal case and find that physically relevant solutions require a nontrivial relation between the conformal and disformal functions. We study the effects of the disformal coupling in an explicit example where the disformal function is quadratic.

- Authors:

- Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States)
- Department of Physics, Swansea University, Singleton Park, Swansea, SA2 8PP (United Kingdom)

- Publication Date:

- OSTI Identifier:
- 22676152

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 06; Other Information: Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ABUNDANCE; ANNIHILATION; COMPUTERIZED SIMULATION; COUPLING; CROSS SECTIONS; EXPANSION; FIELD THEORIES; MASS; MATHEMATICAL SOLUTIONS; NONLUMINOUS MATTER; STRING THEORY

### Citation Formats

```
Dutta, Bhaskar, Jimenez, Esteban, and Zavala, Ivonne, E-mail: dutta@physics.tamu.edu, E-mail: este1985@physics.tamu.edu, E-mail: e.i.zavalacarrasco@swansea.ac.uk.
```*Dark matter relics and the expansion rate in scalar-tensor theories*. United States: N. p., 2017.
Web. doi:10.1088/1475-7516/2017/06/032.

```
Dutta, Bhaskar, Jimenez, Esteban, & Zavala, Ivonne, E-mail: dutta@physics.tamu.edu, E-mail: este1985@physics.tamu.edu, E-mail: e.i.zavalacarrasco@swansea.ac.uk.
```*Dark matter relics and the expansion rate in scalar-tensor theories*. United States. doi:10.1088/1475-7516/2017/06/032.

```
Dutta, Bhaskar, Jimenez, Esteban, and Zavala, Ivonne, E-mail: dutta@physics.tamu.edu, E-mail: este1985@physics.tamu.edu, E-mail: e.i.zavalacarrasco@swansea.ac.uk. Thu .
"Dark matter relics and the expansion rate in scalar-tensor theories". United States.
doi:10.1088/1475-7516/2017/06/032.
```

```
@article{osti_22676152,
```

title = {Dark matter relics and the expansion rate in scalar-tensor theories},

author = {Dutta, Bhaskar and Jimenez, Esteban and Zavala, Ivonne, E-mail: dutta@physics.tamu.edu, E-mail: este1985@physics.tamu.edu, E-mail: e.i.zavalacarrasco@swansea.ac.uk},

abstractNote = {We study the impact of a modified expansion rate on the dark matter relic abundance in a class of scalar-tensor theories. The scalar-tensor theories we consider are motivated from string theory constructions, which have conformal as well as disformally coupled matter to the scalar. We investigate the effects of such a conformal coupling to the dark matter relic abundance for a wide range of initial conditions, masses and cross-sections. We find that exploiting all possible initial conditions, the annihilation cross-section required to satisfy the dark matter content can differ from the thermal average cross-section in the standard case. We also study the expansion rate in the disformal case and find that physically relevant solutions require a nontrivial relation between the conformal and disformal functions. We study the effects of the disformal coupling in an explicit example where the disformal function is quadratic.},

doi = {10.1088/1475-7516/2017/06/032},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 06,

volume = 2017,

place = {United States},

year = {Thu Jun 01 00:00:00 EDT 2017},

month = {Thu Jun 01 00:00:00 EDT 2017}

}