13,697 research outputs found
Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature
Compensated isocurvature perturbations (CIPs) are primordial fluctuations
that balance baryon and dark-matter isocurvature to leave the total matter
density unperturbed. The effects of CIPs on the cosmic microwave background
(CMB) anisotropies are similar to those produced by weak lensing of the CMB:
smoothing of the power spectrum, and generation of non-Gaussian features.
Previous work considered the CIP effects on the CMB power-spectrum but
neglected to include the CIP effects on estimates of the lensing potential
power spectrum (though its contribution to the non-Gaussian, connected, part of
the CMB trispectrum). Here, the CIP contribution to the standard estimator for
the lensing potential power-spectrum is derived, and along with the CIP
contributions to the CMB power-spectrum, Planck data is used to place limits on
the root-mean-square CIP fluctuations on CMB scales, . The resulting constraint of using this new technique improves on past work by a factor of
. We find that for Planck data our constraints almost reach the
sensitivity of the optimal CIP estimator. The method presented here is
currently the most sensitive probe of the amplitude of a scale-invariant CIP
power spectrum placing an upper limit of at 95% CL. Future
measurements of the large-scale CMB lensing potential power spectrum could
probe CIP amplitudes as low as ().Comment: 24 pages, 9 figures; comments welcome; v2 references correcte
Thermal axion constraints in non-standard thermal histories
There is no direct evidence for radiation domination prior to big-bang
nucleosynthesis, and so it is useful to consider how constraints to
thermally-produced axions change in non-standard thermal histories. In the
low-temperature-reheating scenario, radiation domination begins at temperatures
as low as 1 MeV, and is preceded by significant entropy generation. Axion
abundances are then suppressed, and cosmological limits to axions are
significantly loosened. In a kination scenario, a more modest change to axion
constraints occurs. Future possible constraints to axions and low-temperature
reheating are discussed.Comment: Submitted conference proceedings, based on a talk presented at Dark
Matter '08 in Marina del Rey. Based on work discussed in
Phys.Rev.D77:085020,2008, as well as arXiv:0711.1352. Updated to correct
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Behavior of nozzles and acoustic liners in three-dimensional acoustic fields Quarterly report, 1 Dec. 1969 - 28 Feb. 1970
Frequency responses of supercritical nozzles and acoustic liner
Behavior of nozzles and acoustic liners in three-dimensional acoustic fields Quarterly report, 1 Sep. - 31 Dec. 1969
Theoretical studies and test facility installation for investigating behavior of rocket nozzles and acoustic liners in three dimensional acoustic field
Behavior of nozzles and acoustic liners in three-dimensional acoustic fields Quarterly report, 1 Jun. - 31 Aug. 1970
Updating computer program for determining nozzle admittances to eliminate double-root solution and to fit resultant admittance data curves by statistical mean
Behavior of nozzles and acoustic liners in three-dimensional acoustic fields Quarterly report, 1 Sep. - 31 Nov. 1970
Behavior of nozzles and acoustic liners in three dimensional acoustic field
Behavior of nozzles and acoustic liners in three-dimensional acoustic fields Quarterly report, 1 Mar. - 31 May 1969
Behavior of convergent-divergent nozzles and acoustic liners in three dimensional acoustic field
A Sufficient Condition for the Existence of a Principal Eigenvalue for Nonlocal Diffusion Equations with Applications
Considerable work has gone into studying the properties of nonlocal diffusion
equations. The existence of a principal eigenvalue has been a significant
portion of this work. While there are good results for the existence of a
principal eigenvalue equations on a bounded domain, few results exist for
unbounded domains. On bounded domains, the Krein-Rutman theorem on Banach
spaces is a common tool for showing existence. This article shows that
generalized Krein-Rutman can be used on unbounded domains and that the theory
of positive operators can serve as a powerful tool in the analysis of nonlocal
diffusion equations. In particular, a useful sufficient condition for the
existence of a principal eigenvalue is given
Toughened uni-piece fibrous insulation
A porous body of fibrous, low density silica-based insulation material is at least in part impregnated with a reactive boron oxide containing borosilicate glass frit, a silicon tetraboride fluxing agent and a molybdenum silicide emittance agent. The glass frit, fluxing agent and emittance agent are separately milled to reduce their particle size, then mixed together to produce a slurry in ethanol. The slurry is then applied to the insulation material and sintered to produce the porous body
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