# Observational constraints on dark energy with generalized equations of state

## Abstract

We investigate the effects of viscosity terms depending on the Hubble parameter and its derivatives in the dark energy equation of state. Such terms are possible if dark energy is a fictitious fluid originating from corrections to the Einstein general relativity as is the case for some braneworld inspired models or fourth order gravity. We consider two classes of models whose singularities in the early and late time universe have been studied by testing the models against the dimensionless coordinate distance to Type Ia Supernovae and radio galaxies also including priors on the shift and the acoustic peak parameters. It turns out that both models are able to explain the observed cosmic speed up without the need of phantom (w<-1) dark energy.

- Authors:

- Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II' (Italy) and INFN, Sez. di Napoli, Compl. Univ. Monte S. Angelo, Edificio N, Via Cinthia, I-80126, Naples (Italy)
- Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno (Italy) and INFN, Sez. di Napoli, Via S. Allende, I-84081, Baronissi (Salerno) (Italy)
- Institucio Catalana de Recerca i Estudis Avancats (ICREA) (Spain) and Institut d'Estudis Espacials de Catalunya (IEEC/ICE), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain)
- Department of Applied Physics, National Defence Academy, Hashirimizu Yokosuka 239-8686 (Japan)

- Publication Date:

- OSTI Identifier:
- 20776729

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevD.73.043512; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COORDINATES; CORRECTIONS; COSMOLOGY; DISTANCE; EQUATIONS OF STATE; GENERAL RELATIVITY THEORY; GRAVITATION; NONLUMINOUS MATTER; RADIO GALAXIES; SINGULARITY; SUPERNOVAE; UNIVERSE; VISCOSITY

### Citation Formats

```
Capozziello, S., Cardone, V.F., Elizalde, E., Odintsov, S.D., and Nojiri, S.
```*Observational constraints on dark energy with generalized equations of state*. United States: N. p., 2006.
Web. doi:10.1103/PhysRevD.73.043512.

```
Capozziello, S., Cardone, V.F., Elizalde, E., Odintsov, S.D., & Nojiri, S.
```*Observational constraints on dark energy with generalized equations of state*. United States. doi:10.1103/PhysRevD.73.043512.

```
Capozziello, S., Cardone, V.F., Elizalde, E., Odintsov, S.D., and Nojiri, S. Wed .
"Observational constraints on dark energy with generalized equations of state". United States.
doi:10.1103/PhysRevD.73.043512.
```

```
@article{osti_20776729,
```

title = {Observational constraints on dark energy with generalized equations of state},

author = {Capozziello, S. and Cardone, V.F. and Elizalde, E. and Odintsov, S.D. and Nojiri, S.},

abstractNote = {We investigate the effects of viscosity terms depending on the Hubble parameter and its derivatives in the dark energy equation of state. Such terms are possible if dark energy is a fictitious fluid originating from corrections to the Einstein general relativity as is the case for some braneworld inspired models or fourth order gravity. We consider two classes of models whose singularities in the early and late time universe have been studied by testing the models against the dimensionless coordinate distance to Type Ia Supernovae and radio galaxies also including priors on the shift and the acoustic peak parameters. It turns out that both models are able to explain the observed cosmic speed up without the need of phantom (w<-1) dark energy.},

doi = {10.1103/PhysRevD.73.043512},

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

number = 4,

volume = 73,

place = {United States},

year = {Wed Feb 15 00:00:00 EST 2006},

month = {Wed Feb 15 00:00:00 EST 2006}

}