9,480 research outputs found
On the void explanation of the Cold Spot
The integrated Sachs-Wolfe (ISW) contribution induced on the cosmic microwave
background by the presence of a supervoid as the one detected by Szapudi et al.
(2015) is reviewed in this letter in order to check whether it could explain
the Cold Spot (CS) anomaly. Two different models, previously used for the same
purpose, are considered to describe the matter density profile of the void: a
top hat function and a compensated profile produced by a Gaussian potential.
The analysis shows that, even enabling ellipticity changes or different values
for the dark-energy equation of state parameter , the ISW contribution
due to the presence of the void does not reproduce the properties of the CS.
Finally, the probability of alignment between the void and the CS is also
questioned as an argument in favor of a physical connection between these two
phenomena
The group of strong Galois objects associated to a cocommutative Hopf quasigroup
Let H be a cocommutative faithfully flat Hopf quasigroup in a strict
symmetric monoidal category with equalizers. In this paper we introduce the
notion of (strong) Galois H-object and we prove that the set of isomorphism
classes of (strong) Galois H-objects is a (group) monoid which coincides, in
the Hopf algebra setting, with the Galois group of H-Galois objects introduced
by Chase and Sweedler
Lubrication of DLC Coatings with Two Tris(pentafluoroethyl)trifluorophosphate Anion-Based Ionic Liquids
The lubrication of a Cr-DLC coating with ethyl-dimethyl-2-methoxyethylammonium tris(pentafluoroethyl)trifluoropho-sphate [(NEMM)MOE][FAP] and 1-butyl-1-methylpyrro-lidinium tris(pentafluoroethyl)trifluorophosphate [BMP] [FAP] ionic liquids (ILs) as 1 wt% additives to a polyalphaolefin (PAO 6) was studied. Zinc dialkyldithiophosphate (ZDDP) was also used as reference in order to evaluate the effectiveness of the ILs. Reciprocating ball-on-plate tribological tests at loads of 20 and 40 N were performed. The results showed that both ILs exhibited a friction reduction, especially at the lowest load tested. Antiwear properties were also improved; the PAO 6 + 1% [BMP][FAP] mixture was slightly better, close to the values for PAO 6 + 1% ZDDP. Scanning electron microscopy (SEM) images and X-ray photoelectron spectroscopy (XPS) analysis indicated that the additive–surface interaction was responsible for the tribological improvement
Exploring two-spin internal linear combinations for the recovery of the CMB polarization
We present a methodology to recover cosmic microwave background (CMB)
polarization in which the quantity is linearly combined at
different frequencies using complex coefficients. This is the most general
linear combination of the and Stokes parameters which preserves the
physical coherence of the residual contribution on the CMB estimation. The
approach is applied to the internal linear combination (ILC) and the internal
template fitting (ITF) methodologies. The variance of of the resulting map
is minimized to compute the coefficients of the linear combination. One of the
key aspects of this procedure is that it serves to account for a global
frequency-dependent shift of the polarization phase. Although in the standard
case, in which no global E-B transference depending on frequency is expected in
the foreground components, minimizing is
similar to minimizing and separately (as previous methodologies proceed), multiplying
and by different coefficients induces arbitrary changes in the
polarization angle and it does not preserve the coherence between the spinorial
components. The approach is tested on simulations, obtaining a similar residual
level with respect to the one obtained with other implementations of the ILC,
and perceiving the polarization rotation of a toy model with the frequency
dependence of the Faraday rotation.Comment: 14 pages, 8 figures, 2 tables. Accepted for publication in MNRA
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