EDP Sciences
Free access
Volume 406, Number 1, July IV 2003
Page(s) 37 - 41
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20030778

A&A 406, 37-41 (2003)
DOI: 10.1051/0004-6361:20030778

The Kelvin-Helmholtz instability in an expanding universe and its effect on dark matter

K. A. Malik1 and D. R. Matravers2

1  GRECO, Institut d'Astrophysique de Paris, CNRS, 98bis Boulevard Arago, 75014 Paris, France
2  Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 2EG, UK

(Received 16 January 2003 / Accepted 12 May 2003)

We extend the Kelvin-Helmholtz instability to an expanding background. We study the evolution of a non-viscous irrotational fluid and find that for wavelengths much smaller than the Hubble scale small perturbations of the fluid are unstable for wavenumbers larger than a critical value. We then apply this result in the early universe, treating cold dark matter as a classical fluid with vanishing background pressure.

Key words: instabilities -- cosmology: theory -- cosmology: dark matter

Offprint request: K. A. Malik, malik@iap.fr

© ESO 2003