# Cosmological implications of unimodular gravity

## Abstract

We consider a model of gravity and matter fields which is invariant only under unimodular general coordinate transformations (GCT). The determinant of the metric is treated as a separate field which transforms as a scalar under unimodular GCT. Furthermore we also demand that the theory is invariant under a new global symmetry which we call generalized conformal invariance. We study the cosmological implications of the resulting theory. We show that this theory gives a fit to the high-z supernova data which is identical to the standard Big Bang model. Hence we require some other cosmological observations to test the validity of this model. We also consider some models which do not obey the generalized conformal invariance. In these models we can fit the supernova data without introducing the standard cosmological constant term. Furthermore these models introduce only one dark component and hence solve the coincidence problem of dark matter and dark energy.

- Authors:

- Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)
- Physical Research Laboratory, Ahmedabad 380 009 (India)

- Publication Date:

- OSTI Identifier:
- 22279673

- 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:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; CONFORMAL INVARIANCE; COORDINATES; COSMOLOGICAL CONSTANT; COSMOLOGY; GRAVITATION; METRICS; NONLUMINOUS MATTER; SCALARS; SUPERNOVAE; SYMMETRY; TRANSFORMATIONS

### Citation Formats

```
Jain, Pankaj, Jaiswal, Atul, Karmakar, Purnendu, Kashyap, Gopal, and Singh, Naveen K., E-mail: pkjain@iitk.ac.in, E-mail: atijazz@iitk.ac.in, E-mail: purnendu@iitk.ac.in, E-mail: gopal@iitk.ac.in, E-mail: naveenks@prl.res.in.
```*Cosmological implications of unimodular gravity*. United States: N. p., 2012.
Web. doi:10.1088/1475-7516/2012/11/003.

```
Jain, Pankaj, Jaiswal, Atul, Karmakar, Purnendu, Kashyap, Gopal, & Singh, Naveen K., E-mail: pkjain@iitk.ac.in, E-mail: atijazz@iitk.ac.in, E-mail: purnendu@iitk.ac.in, E-mail: gopal@iitk.ac.in, E-mail: naveenks@prl.res.in.
```*Cosmological implications of unimodular gravity*. United States. doi:10.1088/1475-7516/2012/11/003.

```
Jain, Pankaj, Jaiswal, Atul, Karmakar, Purnendu, Kashyap, Gopal, and Singh, Naveen K., E-mail: pkjain@iitk.ac.in, E-mail: atijazz@iitk.ac.in, E-mail: purnendu@iitk.ac.in, E-mail: gopal@iitk.ac.in, E-mail: naveenks@prl.res.in. Thu .
"Cosmological implications of unimodular gravity". United States. doi:10.1088/1475-7516/2012/11/003.
```

```
@article{osti_22279673,
```

title = {Cosmological implications of unimodular gravity},

author = {Jain, Pankaj and Jaiswal, Atul and Karmakar, Purnendu and Kashyap, Gopal and Singh, Naveen K., E-mail: pkjain@iitk.ac.in, E-mail: atijazz@iitk.ac.in, E-mail: purnendu@iitk.ac.in, E-mail: gopal@iitk.ac.in, E-mail: naveenks@prl.res.in},

abstractNote = {We consider a model of gravity and matter fields which is invariant only under unimodular general coordinate transformations (GCT). The determinant of the metric is treated as a separate field which transforms as a scalar under unimodular GCT. Furthermore we also demand that the theory is invariant under a new global symmetry which we call generalized conformal invariance. We study the cosmological implications of the resulting theory. We show that this theory gives a fit to the high-z supernova data which is identical to the standard Big Bang model. Hence we require some other cosmological observations to test the validity of this model. We also consider some models which do not obey the generalized conformal invariance. In these models we can fit the supernova data without introducing the standard cosmological constant term. Furthermore these models introduce only one dark component and hence solve the coincidence problem of dark matter and dark energy.},

doi = {10.1088/1475-7516/2012/11/003},

journal = {Journal of Cosmology and Astroparticle Physics},

issn = {1475-7516},

number = 11,

volume = 2012,

place = {United States},

year = {2012},

month = {11}

}