1,106 research outputs found
Manifestations of a spatial variation of fundamental constants on atomic clocks, Oklo, meteorites, and cosmological phenomena
The remarkable detection of a spatial variation in the fine-structure
constant, alpha, from quasar absorption systems must be independently confirmed
by complementary searches. In this letter, we discuss how terrestrial
measurements of time-variation of the fundamental constants in the laboratory,
meteorite data, and analysis of the Oklo nuclear reactor can be used to
corroborate the spatial variation seen by astronomers. Furthermore, we show
that spatial variation of the fundamental constants may be observable as
spatial anisotropy in the cosmic microwave background, the accelerated
expansion (dark energy), and large-scale structure of the Universe.Comment: 4 page
Faraday Rotation as a diagnostic of Galactic foreground contamination of CMB maps
The contribution from the residuals of the foreground can have a significant
impact on the temperature maps of the Cosmic Microwave Background (CMB).
Mostly, the focus has been on the galactic plane, when foreground cleaning has
taken place. However, in this paper, we will investigate the possible
foreground contamination, from sources outside the galactic plane in the CMB
maps. We will analyze the correlation between the Faraday rotation map and the
CMB temperature map. The Faraday rotation map is dependent on the galactic
magnetic field, as well as the thermal electron density, and both may
contribute to the CMB temperature. We find that the standard deviation for the
mean cross correlation deviate from that of simulations at the 99.9% level.
Additionally, a comparison between the CMB temperature extrema and the extremum
points of the Faraday rotation is also performed, showing a general overlap
between the two. Also we find that the CMB Cold Spot is located at an area of
strong negative cross correlation, meaning that it may be explained by a
galactic origin. Further, we investigate nearby supernova remnants in the
galaxy, traced by the galactic radio loops. These super nova remnants are
located at high and low galactic latitude, and thus well outside the galactic
plane. We find some correlation between the Faraday Rotation and the CMB
temperature, at select radio loops. This indicate, that the galactic
foregrounds may affect the CMB, at high galactic latitudesComment: 13 pages, 22 figures, 6 table
Estimating small angular scale CMB anisotropy with high resolution N-body simulations: weak lensing
We estimate the impact of weak lensing by strongly nonlinear cosmological
structures on the cosmic microwave background. Accurate calculation of large
multipoles requires N-body simulations and ray-tracing schemes with both
high spatial and temporal resolution. To this end we have developed a new code
that combines a gravitational Adaptive Particle-Particle, Particle-Mesh (AP3M)
solver with a weak lensing evaluation routine. The lensing deviations are
evaluated while structure evolves during the simulation so that all evolution
steps--rather than just a few outputs--are used in the lensing computations.
The new code also includes a ray-tracing procedure that avoids periodicity
effects in a universe that is modeled as a 3-D torus in the standard way.
Results from our new simulations are compared with previous ones based on
Particle-Mesh simulations. We also systematically investigate the impact of box
volume, resolution, and ray-tracing directions on the variance of the computed
power spectra. We find that a box size of Mpc is sufficient to
provide a robust estimate of the weak lensing angular power spectrum in the
-interval (2,000--7,000). For a reaslistic cosmological model the power
takes on values of a few in this
interval, which suggests that a future detection is feasible and may explain
the excess power at high in the BIMA and CBI observations.Comment: 49 pages, 13 figures, accepted for publication in Ap
Theory of Cylindrical Tubules and Helical Ribbons of Chiral Lipid Membranes
We present a general theory for the equilibrium structure of cylindrical
tubules and helical ribbons of chiral lipid membranes. This theory is based on
a continuum elastic free energy that permits variations in the direction of
molecular tilt and in the curvature of the membrane. The theory shows that the
formation of tubules and helical ribbons is driven by the chirality of the
membrane. Tubules have a first-order transition from a uniform state to a
helically modulated state, with periodic stripes in the tilt direction and
ripples in the curvature. Helical ribbons can be stable structures, or they can
be unstable intermediate states in the formation of tubules.Comment: 43 pages, including 12 postscript figures, uses REVTeX 3.0 and
epsf.st
Phantom Accretion onto the Schwarzschild de-Sitter Black Hole
We deal with phantom energy accretion onto the Schwarzschild de-Sitter black
hole. The energy flux conservation, relativistic Bernoulli equation and mass
flux conservation equation are formulated to discuss the phantom accretion. We
discuss the conditions for critical accretion. It is found that mass of the
black hole decreases due to phantom accretion. There exist two critical points
which lie in the exterior of horizons (black hole and cosmological horizons).
The results for the phantom energy accretion onto the Schwarzschild black hole
can be recovered by taking .Comment: 9 pages, no figur
Structures and orientational transitions in thin films of tilted hexatic smectics
We present detailed systematic studies of structural transformations in thin
liquid crystal films with the smectic-C to hexatic phase transition. For the
first time all possible structures reported in the literature are observed for
one material (5 O.6) at the variation of temperature and thickness. In unusual
modulated structures the equilibrium period of stripes is twice with respect to
the domain size. We interpret these patterns in the frame work of
phenomenological Landau type theory, as equilibrium phenomena produced by a
natural geometric frustration in a system having spontaneous splay distortion.Comment: 7 pages, 6 figure
On the Rees-Sciama effect: maps and statistics
Small maps of the Rees-Sciama (RS) effect are simulated by using an
appropriate N-body code and a certain ray-tracing procedure. A method designed
for the statistical analysis of cosmic microwave background (CMB) maps is
applied to study the resulting simulations. These techniques, recently proposed
--by our team-- to consider lens deformations of the CMB, are adapted to deal
with the RS effect. This effect and the deviations from Gaussianity associated
to it seem to be too small to be detected in the near future. This conclusion
follows from our estimation of both the RS angular power spectrum and the RS
reduced n-direction correlation functions for n<7.Comment: 11 pages, 13 figures, to appear in MNRA
Instability of reconstruction of the low CMB multipoles
We discuss the problem of the bias of the Internal Linear Combination (ILC)
CMB map and show that it is closely related to the coefficient of
cross-correlation K(l) of the true CMB and the foreground for each multipole l.
We present analysis of the cross-correlation for the WMAP ILC quadrupole and
octupole from the first (ILC(I)) and the third (ILC(III)) year data releases
and show that these correlations are about -0.52-0.6. Analysing 10^4 Monte
Carlo simulations of the random Gaussian CMB signals, we show that the
distribution function for the corresponding coefficient of the
cross-correlation has a polynomial shape P(K,l)\propto(1-K^2)^(l-1). We show
that the most probable value of the cross-correlation coefficient of the ILC
and foreground quadrupole has two extrema at K ~= +/-0.58$. Thus, the ILC(III)
quadrupole represents the most probable value of the coefficient K. We analyze
the problem of debiasing of the ILC CMB and pointed out that reconstruction of
the bias seems to be very problematic due to statistical uncertainties. In
addition, instability of the debiasing illuminates itself for the quadrupole
and octupole components through the flip-effect, when the even (l+m) modes can
be reconstructed with significant error. This error manifests itself as
opposite, in respect to the true sign of even low multipole modes, and leads to
significant changes of the coefficient of cross-correlation with the
foreground. We show that the CMB realizations, whose the sign of quadrupole
(2,0) component is negative (and the same, as for all the foregrounds), the
corresponding probability to get the positive sign after implementation of the
ILC method is about 40%.Comment: 11 pages, 5 figure
A window to quantum gravity phenomena in the emergence of the seeds of cosmic structure
Inflationary cosmology has, in the last few years,received a strong dose of
support from observations. The fact that the fluctuation spectrum can be
extracted from the inflationary scenario through an analysis that involves
quantum field theory in curved space-time, and that it coincides with the
observational data has lead to a certain complacency in the community, which
prevents the critical analysis of the obscure spots in the derivation. We argue
here briefly, as we have discussed in more detail elsewhere, that there is
something important missing in our understanding of the origin of the seeds of
Cosmic Structure, as is evidenced by the fact that in the standard accounts the
inhomogeneity and anisotropy of our universe seems to emerge from an exactly
homogeneous andisotropic initial state through processes that do not break
those symmetries. This article gives a very brief recount of the problems faced
by the arguments based on established physics. The conclusion is that we need
some new physics to be able to fully address the problem. The article then
exposes one avenue that has been used to address the central issue and
elaborates on the degree to which, the new approach makes different predictions
from the standard analyses. The approach is inspired on Penrose's proposals
that Quantum Gravity might lead to a real, dynamical collapse of the wave
function, a process that we argued has the properties needed to extract us from
the theoretical impasse described above.Comment: 13 pages, 3 figures. To appear in DICE 2008 conference proceeding
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