# Cosmological perturbations through a non-singular ghost-condensate/Galileon bounce

## Abstract

We study the propagation of super-horizon cosmological perturbations in a non-singular bounce spacetime. The model we consider combines a ghost condensate with a Galileon term in order to induce a ghost-free bounce. Our calculation is performed in harmonic gauge, which ensures that the linearized equations of motion remain well-defined and non-singular throughout. We find that, despite the fact that near the bounce the speed of sound becomes imaginary, super-horizon curvature perturbations remain essentially constant across the bounce. In fact, we show that there is a time close to the bounce where curvature perturbations of all wavelengths are required to be momentarily exactly constant. We relate our calculations to those performed in other gauges, and comment on the relation to previous results in the literature.

- Authors:

- Max Planck Institute for Gravitational Physics (Albert Einstein Institute), 14476 Potsdam (Germany)
- Department of Physics, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104-6395 (United States)

- Publication Date:

- OSTI Identifier:
- 22373480

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2014; Journal Issue: 07; Other Information: Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EQUATIONS OF MOTION; PERTURBATION THEORY; SOUND WAVES; SPACE-TIME; VELOCITY

### Citation Formats

```
Battarra, Lorenzo, Koehn, Michael, Lehners, Jean-Luc, and Ovrut, Burt A., E-mail: lorenzo.battarra@aei.mpg.de, E-mail: michael.koehn@aei.mpg.de, E-mail: jlehners@aei.mpg.de, E-mail: ovrut@elcapitan.hep.upenn.edu.
```*Cosmological perturbations through a non-singular ghost-condensate/Galileon bounce*. United States: N. p., 2014.
Web. doi:10.1088/1475-7516/2014/07/007.

```
Battarra, Lorenzo, Koehn, Michael, Lehners, Jean-Luc, & Ovrut, Burt A., E-mail: lorenzo.battarra@aei.mpg.de, E-mail: michael.koehn@aei.mpg.de, E-mail: jlehners@aei.mpg.de, E-mail: ovrut@elcapitan.hep.upenn.edu.
```*Cosmological perturbations through a non-singular ghost-condensate/Galileon bounce*. United States. doi:10.1088/1475-7516/2014/07/007.

```
Battarra, Lorenzo, Koehn, Michael, Lehners, Jean-Luc, and Ovrut, Burt A., E-mail: lorenzo.battarra@aei.mpg.de, E-mail: michael.koehn@aei.mpg.de, E-mail: jlehners@aei.mpg.de, E-mail: ovrut@elcapitan.hep.upenn.edu. Tue .
"Cosmological perturbations through a non-singular ghost-condensate/Galileon bounce". United States. doi:10.1088/1475-7516/2014/07/007.
```

```
@article{osti_22373480,
```

title = {Cosmological perturbations through a non-singular ghost-condensate/Galileon bounce},

author = {Battarra, Lorenzo and Koehn, Michael and Lehners, Jean-Luc and Ovrut, Burt A., E-mail: lorenzo.battarra@aei.mpg.de, E-mail: michael.koehn@aei.mpg.de, E-mail: jlehners@aei.mpg.de, E-mail: ovrut@elcapitan.hep.upenn.edu},

abstractNote = {We study the propagation of super-horizon cosmological perturbations in a non-singular bounce spacetime. The model we consider combines a ghost condensate with a Galileon term in order to induce a ghost-free bounce. Our calculation is performed in harmonic gauge, which ensures that the linearized equations of motion remain well-defined and non-singular throughout. We find that, despite the fact that near the bounce the speed of sound becomes imaginary, super-horizon curvature perturbations remain essentially constant across the bounce. In fact, we show that there is a time close to the bounce where curvature perturbations of all wavelengths are required to be momentarily exactly constant. We relate our calculations to those performed in other gauges, and comment on the relation to previous results in the literature.},

doi = {10.1088/1475-7516/2014/07/007},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 07,

volume = 2014,

place = {United States},

year = {Tue Jul 01 00:00:00 EDT 2014},

month = {Tue Jul 01 00:00:00 EDT 2014}

}