3,864 research outputs found
Effects of a primordial magnetic field with log-normal distribution on the cosmic microwave background
We study the effect of primordial magnetic fields (PMFs) on the anisotropies
of the cosmic microwave background (CMB). We assume the spectrum of PMFs is
described by log-normal distribution which has a characteristic scale, rather
than power-law spectrum. This scale is expected to reflect the generation
mechanisms and our analysis is complementary to previous studies with power-law
spectrum. We calculate power spectra of energy density and Lorentz force of the
log-normal PMFs, and then calculate CMB temperature and polarization angular
power spectra from scalar, vector, and tensor modes of perturbations generated
from such PMFs. By comparing these spectra with WMAP7, QUaD, CBI, Boomerang,
and ACBAR data sets, we find that the current CMB data set places the strongest
constraint at Mpc with the upper limit
nG.Comment: 14 pages, 6 figure
Constraints on the neutrino mass and the primordial magnetic field from the matter density fluctuation parameter
We have made an analysis of limits on the neutrino mass based upon the
formation of large-scale structure in the presence of a primordial magnetic
field. We find that a new upper bound on the neutrino mass is possible based
upon fits to the cosmic microwave background and matter power spectrum when the
existing independent constraints on the matter density fluctuation parameter
and the primordial magnetic field are taken into account.Comment: 6 pages, 2 figures, final version to appear in Phys. Rev. D, to match
proof
Primordial Magnetic Field Effects on the CMB and Large Scale Structure
Magnetic fields are everywhere in nature and they play an important role in
every astronomical environment which involves the formation of plasma and
currents. It is natural therefore to suppose that magnetic fields could be
present in the turbulent high temperature environment of the big bang. Such a
primordial magnetic field (PMF) would be expected to manifest itself in the
cosmic microwave background (CMB) temperature and polarization anisotropies,
and also in the formation of large- scale structure. In this review we
summarize the theoretical framework which we have developed to calculate the
PMF power spectrum to high precision. Using this formulation, we summarize
calculations of the effects of a PMF which take accurate quantitative account
of the time evolution of the cut off scale. We review the constructed numerical
program, which is without approximation, and an improvement over the approach
used in a number of previous works for studying the effect of the PMF on the
cosmological perturbations. We demonstrate how the PMF is an important
cosmological physical process on small scales. We also summarize the current
constraints on the PMF amplitude and the power spectral index
which have been deduced from the available CMB observational data by using our
computational framework.Comment: 26 pages, 13 figures. arXiv admin note: substantial text overlap with
arXiv:1001.201
New Constraints on the Primordial Magnetic Field
We present the newest statistical and numerical analysis of the matter and
cosmic microwave background power spectrum with effects of the primordial
magnetic field (PMF) included. New limits to the PMF strength and power
spectral index are obtained based upon the accumulated data for both the matter
and CMB power spectra on small angular scales. We find that a maximum develops
in the probability distribution for a magnitude of the PMF of nG on a comoving scale of at 1 Mpc, corresponding
to upper limits of and . While for the power spectral index we find
, corresponding to upper
limits of and . This result provides new constraints on models for magnetic
field generation and the physics of the early universe. We conclude that future
observational programs for the CMB and matter power spectrum will likely
provide not only upper limits but also lower limits to the PMF parameters.Comment: 7 pages, 3 figures, 1 table, final version to appear in Phys. Rev. D,
to match proof
Neutrino mass effects on vector and tensor CMB anisotropies in the presence of a primordial magnetic field
If a primordial magnetic field (PMF) is present during photon decoupling and
afterward, a finite neutrino mass can affect all modes of the CMB. In this
work, we expand on earlier studies of the scalar mode effects by constructing
the vector and tensor mode equations in the presence of massive neutrinos and a
PMF. We compute the power spectrum of the various modes in an illustrative
example and find that the neutrino mass can significantly affect the vector and
tensor modes when a PMF exists, while the effects are negligible for no PMF.
The most prominent result of the present analysis is the behavior of the EE
component of the tensor mode at low multipoles. For massive neutrinos the EE
mode can become comparable to the observed primary anisotropy. Therefore, if
and when the EE mode power spectrum is measured at low multipoles the
possibility exists to place a strong constraint on the sum of the neutrino
masses.Comment: 11 pages, 8 figure
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