Author:
Koksbang Sofie Marie,Räsänen Syksy
Abstract
Abstract
Light propagation in cosmology is usually studied in the
geometrical optics approximation which requires the spacetime
curvature to be much smaller than the light wavenumber. However, for
non-fuzzy particle dark matter the curvature is concentrated in
widely separated spikes at particle location. If the particle mass
is localised within a Compton wavelength, then for masses
≳104 GeV the curvature is larger than the energy of CMB
photons.
We consider a post-geometrical optics approximation that includes
curvature. Photons gain a gravity-induced mass when travelling through
dark matter, and light paths are not null nor geodesic. We find that
the correction to the redshift is negligible. For the angular diameter
distance, we show how the small average density emerges from the large
local spikes when integrating along the light ray. We find that there
can be a large correction to the angular diameter distance even for
photon energies much larger than the curvature. This may allow to set
a strong upper limit on the mass of dark matter particles. We discuss
open issues related to the validity of our approximations.
Subject
Astronomy and Astrophysics
Cited by
1 articles.
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