6 research outputs found
Nielsen-Olesen vortex in varying-alpha theories
We consider soliton solutions to Bekenstein's theory, for which the fine
structure constant is allowed to vary due to the
presence of a dielectric field pervading the vacuum. More specifically we
investigate the effects of a varying upon a complex scalar field with
a U(1) electromagnetic gauge symmetry subject to spontaneous symmetry breaking.
We find vortex solutions to this theory, similar to the Nielsen-Olesen vortex.
Near the vortex core the electric charge is typically much larger than far away
from the string, lending these strings a superconducting flavour. In general
the dielectric field coats the usual local string with a global string
envelope. We discuss the cosmological implications of networks of such strings,
with particular emphasis on their ability to generate inhomogeneous
recombination scenarios. We also consider the possibility of the dielectric
being a charged free field. Even though the vacuum of such a field is trivial,
we find that the dielectric arranges itself in the shape of a local string,
with a quantized magnetic flux at the core -- presumably borrowing these
topological features from the underlying Nielsen-Olesen vortex.Comment: 7 pages, 1 figur
CMBfit: Rapid WMAP likelihood calculations with normal parameters
We present a method for ultra-fast confrontation of the WMAP cosmic microwave
background observations with theoretical models, implemented as a publicly
available software package called CMBfit, useful for anyone wishing to measure
cosmological parameters by combining WMAP with other observations. The method
takes advantage of the underlying physics by transforming into a set of
parameters where the WMAP likelihood surface is accurately fit by the
exponential of a quartic or sextic polynomial. Building on previous physics
based approximations by Hu et.al., Kosowsky et.al. and Chu et.al., it combines
their speed with precision cosmology grade accuracy. A Fortran code for
computing the WMAP likelihood for a given set of parameters is provided,
pre-calibrated against CMBfast, accurate to Delta lnL ~ 0.05 over the entire
2sigma region of the parameter space for 6 parameter ``vanilla'' Lambda CDM
models. We also provide 7-parameter fits including spatial curvature,
gravitational waves and a running spectral index.Comment: 14 pages, 8 figures, References added, accepted for publication in
Phys.Rev.D., a Fortran code can be downloaded from
http://space.mit.edu/home/tegmark/cmbfit