11,431 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
Signatures of S-wave bound-state formation in finite volume
We discuss formation of an S-wave bound-state in finite volume on the basis
of L\"uscher's phase-shift formula.It is found that although a bound-state pole
condition is fulfilled only in the infinite volume limit, its modification by
the finite size corrections is exponentially suppressed by the spatial extent
in a finite box . We also confirm that the appearance of the S-wave
bound state is accompanied by an abrupt sign change of the S-wave scattering
length even in finite volume through numerical simulations. This distinctive
behavior may help us to discriminate the loosely bound state from the lowest
energy level of the scattering state in finite volume simulations.Comment: 25 pages, 30 figures; v2: typos corrected and two references added,
v3: final version to appear in PR
Constraints on the Primordial Magnetic Field from
A primordial magnetic field (PMF) can affect the evolution of density field
fluctuations in the early universe.In this paper we constrain the PMF amplitude
and power spectral index by comparing calculated
density field fluctuations with observational data, i.e. the number density
fluctuation of galaxies.We show that the observational constraints on
cosmological density fluctuations, as parameterized by , lead to
strong constraints on the amplitude and spectral index of the PMF.Comment: 11 pages, 1 figure, accepted for publication as Phys. Rev.
Constraints on the Evolution of the Primordial Magnetic Field from the Small-Scale Cosmic Microwave Background Angular Anisotropy
Recent observations of the cosmic microwave background (CMB) have extended
the measured power spectrum to higher multipoles 1000, and there
appears to be possible evidence for excess power on small angular scales. The
primordial magnetic field (PMF) can strongly affect the CMB power spectrum and
the formation of large scale structure. In this paper, we calculate the CMB
temperature anisotropies generated by including a power-law magnetic field at
the photon last-scattering surface (PLSS). We then deduce an upper limit on the
PMF based on our theoretical analysis of the power excess on small angular
scales. We have taken into account several important effects such as the
modified matter sound speed in the presence of a magnetic field. An upper limit
to the field strength of 4.7 nG at the present scale of 1
Mpc is deduced. This is obtained by comparing the calculated theoretical result
including the Sunyaev-Zeldovich (SZ) effect with recent observed data on the
small-scale CMB anisotropies from the
(WMAP), the Cosmic Background Imager (CBI), and the Arcminute Cosmology
Bolometer Array Receiver (ACBAR). We discuss several possible mechanisms for
the generation and evolution of the PMF.Comment: 27 pages, 4 figures, accepted to ApJ April 10, 200
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
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