Cosmological simulations with disformally coupled symmetron fields

Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
e-mail: robert.hagala@astro.uio.no

Received: 29 April 2015
Accepted: 29 September 2015

Abstract

Context. We investigate statistical properties of the distribution of matter at redshift zero in disformal gravity by using N-body simulations. The disformal model studied here consists of a conformally coupled symmetron field with an additional exponential disformal term.

Aims. We conduct cosmological simulations to discover the impact of the new disformal terms in the matter power spectrum, halo mass function, and radial profile of the scalar field.

Methods. We calculated the disformal geodesic equation and the equation of motion for the scalar field. We then implemented these equations into the N-body code Isis, which is a modified gravity version of the code Ramses.

Results. The presence of a conformal symmetron field increases both the power spectrum and mass function compared to standard gravity on small scales. Our main finding is that the newly added disformal terms tend to counteract these effects and can make the evolution slightly closer to standard gravity. We finally show that the disformal terms give rise to oscillations of the scalar field in the centre of the dark matter haloes.