Journal Article

On the effects of coupled scalar fields on structure formation

Baojiu Li and John D. Barrow

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 413, issue 1, pages 262-270
Published in print May 2011 | ISSN: 0035-8711
Published online April 2011 | e-ISSN: 1365-2966 | DOI:
On the effects of coupled scalar fields on structure formation

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A coupling between a scalar field (representing the dark energy) and dark matter could produce rich phenomena in cosmology. It affects cosmic structure formation mainly through the fifth force, a velocity-dependent force that acts parallel to particle’s direction of motion and proportional to its speed, an effective rescaling of the particle masses and a modified background expansion rate. In many cases, these effects entangle and it is difficult to see which is the dominant one. Here, we perform N-body simulations to study their qualitative behaviour and relative importance in affecting the key structure formation observables, for a model with exponential scalar field coupling. We find that the fifth force, a prominent example of the scalar-coupling effects, is far less important than the rescaling of particle mass or the modified expansion rate in its effects on the matter power spectrum and mass function. In particular, the rescaling of particle masses is shown to be the key factor leading to less concentration of particles in haloes than in Λcold dark matter, a pattern which is also observed in previous independent coupled scalar field simulations.

Keywords: gravitation; methods: numerical; galaxies: haloes; cosmology: theory; dark energy; large-scale structure of Universe

Journal Article.  6060 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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