# Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath

## Abstract

The effects of bulk viscosity are examined for inflationary dynamics in which dissipation and thermalization are present. A complete stability analysis is done for the background inflaton evolution equations, which includes both inflaton dissipation and radiation bulk viscous effects. Three representative approaches of bulk viscous irreversible thermodynamics are analyzed: the Eckart noncausal theory, the linear and causal theory of Israel-Stewart and a more recent nonlinear and causal bulk viscous theory. It is found that the causal theories allow for larger bulk viscosities before encountering an instability in comparison to the noncausal Eckart theory. It is also shown that the causal theories tend to suppress the radiation production due to bulk viscous pressure, because of the presence of relaxation effects implicit in these theories. Bulk viscosity coefficients derived from quantum field theory are applied to warm inflation model building and an analysis is made of the effects to the duration of inflation. The treatment of bulk pressure would also be relevant to the reheating phase after inflation in cold inflation dynamics and during the radiation dominated regime, although very little work in both areas has been done; the methodology developed in this paper could be extended to apply to these othermore »

- Authors:

- Departamento de Física Teórica y del Cosmos, Universidad de Granada, Granada-18071 (Spain)
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3JZ (United Kingdom)
- Departamento de Física Teórica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil)

- Publication Date:

- OSTI Identifier:
- 22279827

- Resource Type:
- Journal Article

- Journal Name:
- Journal of Cosmology and Astroparticle Physics

- Additional Journal Information:
- Journal Volume: 2012; Journal Issue: 11; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CAUSALITY; COMPARATIVE EVALUATIONS; COSMOLOGY; EVOLUTION; FIELD EQUATIONS; INFLATIONARY UNIVERSE; INFLATONS; NONLINEAR PROBLEMS; QUANTUM FIELD THEORY; RELAXATION; STABILITY; THERMALIZATION; THERMODYNAMICS; VISCOSITY

### Citation Formats

```
Bastero-Gil, Mar, Cerezo, Rafael, Berera, Arjun, Ramos, Rudnei O., and Vicente, Gustavo S., E-mail: mbg@ugr.es, E-mail: ab@ph.ed.ac.uk, E-mail: cerezo@ugr.es, E-mail: rudnei@uerj.br, E-mail: gsvicente@uerj.br.
```*Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath*. United States: N. p., 2012.
Web. doi:10.1088/1475-7516/2012/11/042.

```
Bastero-Gil, Mar, Cerezo, Rafael, Berera, Arjun, Ramos, Rudnei O., & Vicente, Gustavo S., E-mail: mbg@ugr.es, E-mail: ab@ph.ed.ac.uk, E-mail: cerezo@ugr.es, E-mail: rudnei@uerj.br, E-mail: gsvicente@uerj.br.
```*Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath*. United States. doi:10.1088/1475-7516/2012/11/042.

```
Bastero-Gil, Mar, Cerezo, Rafael, Berera, Arjun, Ramos, Rudnei O., and Vicente, Gustavo S., E-mail: mbg@ugr.es, E-mail: ab@ph.ed.ac.uk, E-mail: cerezo@ugr.es, E-mail: rudnei@uerj.br, E-mail: gsvicente@uerj.br. Thu .
"Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath". United States. doi:10.1088/1475-7516/2012/11/042.
```

```
@article{osti_22279827,
```

title = {Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath},

author = {Bastero-Gil, Mar and Cerezo, Rafael and Berera, Arjun and Ramos, Rudnei O. and Vicente, Gustavo S., E-mail: mbg@ugr.es, E-mail: ab@ph.ed.ac.uk, E-mail: cerezo@ugr.es, E-mail: rudnei@uerj.br, E-mail: gsvicente@uerj.br},

abstractNote = {The effects of bulk viscosity are examined for inflationary dynamics in which dissipation and thermalization are present. A complete stability analysis is done for the background inflaton evolution equations, which includes both inflaton dissipation and radiation bulk viscous effects. Three representative approaches of bulk viscous irreversible thermodynamics are analyzed: the Eckart noncausal theory, the linear and causal theory of Israel-Stewart and a more recent nonlinear and causal bulk viscous theory. It is found that the causal theories allow for larger bulk viscosities before encountering an instability in comparison to the noncausal Eckart theory. It is also shown that the causal theories tend to suppress the radiation production due to bulk viscous pressure, because of the presence of relaxation effects implicit in these theories. Bulk viscosity coefficients derived from quantum field theory are applied to warm inflation model building and an analysis is made of the effects to the duration of inflation. The treatment of bulk pressure would also be relevant to the reheating phase after inflation in cold inflation dynamics and during the radiation dominated regime, although very little work in both areas has been done; the methodology developed in this paper could be extended to apply to these other problems.},

doi = {10.1088/1475-7516/2012/11/042},

journal = {Journal of Cosmology and Astroparticle Physics},

issn = {1475-7516},

number = 11,

volume = 2012,

place = {United States},

year = {2012},

month = {11}

}