10,198 research outputs found
Relative categories: Another model for the homotopy theory of homotopy theories
We lift Charles Rezk's complete Segal space model structure on the category
of simplicial spaces to a Quillen equivalent one on the category of relative
categories.Comment: 27 pages. Updated to correct typographical error
Declining Rotation Curve and Brown Dwarf MACHOs
If the Galactic rotation speed at the Solar circle is km s
or smaller, which is supported by several recent studies, the rotation curve of
the Galaxy could be declining in the outermost region. Motivated by this, we
investigate the effect of such declining rotation curve on the estimate of the
MACHO mass and the fractional contribution of the MACHOs to the Galactic dark
halo. Using Hernquist and Plummer halo models instead of the standard halo
model, we find that the MACHO mass could be significantly smaller than that for
the standard halo case. In particular, there exists a certain set of halo
parameters for which the MACHO mass is 0.1 or less and at the same
time the MACHO contribution to the total mass of the halo is almost 100 %. This
result indicates that a halo which consists solely of brown dwarfs can be
consistent with both of the observed microlensing properties and the
constraints from the rotation curve, provided the outer rotation curve is
indeed declining.Comment: 8 pages and 4 figures, accepted for publication in ApJ Letter
The Nature of Two-Directional Intergenerational Transfers of Money and Time: An Empirical Analysis
Order statistics and the linear assignment problem
Under mild conditions on the distribution functionF, we analyze the asymptotic behavior in expectation of the smallest order statistic, both for the case thatF is defined on (–, +) and for the case thatF is defined on (0, ). These results yield asymptotic estimates of the expected optiml value of the linear assignment problem under the assumption that the cost coefficients are independent random variables with distribution functionF.asymptotic analysis;linear assignment problem;order statistic
Stabilizing intrinsic defects in SnO
TThe magnetism and electronic structure of Li-doped SnO are
investigated using first-principles LDA/LDA calculations. We find that Li
induces magnetism in SnO when doped at the Sn site but becomes
non-magnetic when doped at the O and interstitial sites. The calculated
formation energies show that Li prefers the Sn site as compared with the O
site, in agreement with previous experimental works. The interaction of Li with
native defects (Sn V and O V vacancies) is also
studied, and we find that Li not only behaves as a spin polarizer, but also a
vacancy stabilizer, i.e. Li significantly reduces the defect formation energies
of the native defects and helps the stabilization of magnetic oxygen vacancies.
The electronic densities of states reveals that these systems, where the Fermi
level touches the conduction (valence) band, are non-magnetic
(magnetic).cancies. The electronic densities of states reveal that those
systems, where the Fermi levels touch the conduction (valence) band, are
non-magnetic (magnetic).Comment: Phys. Rev. B (2013), Accepte
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