1,947 research outputs found
The behavior of the NPMLE of a decreasing density near the boundaries of the support
We investigate the behavior of the nonparametric maximum likelihood estimator
for a decreasing density near the boundaries of the support of
. We establish the limiting distribution of , where
we need to distinguish between different values of . Similar
results are obtained for the upper endpoint of the support, in the case it is
finite. This yields consistent estimators for the values of at the
boundaries of the support. The limit distribution of these estimators is
established and their performance is compared with the penalized maximum
likelihood estimator.Comment: Published at http://dx.doi.org/10.1214/009053606000000100 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Asymptotic normality of the -error of the Grenander estimator
We investigate the limit behavior of the -distance between a decreasing
density and its nonparametric maximum likelihood estimator for
. Due to the inconsistency of at zero, the case
turns out to be a kind of transition point. We extend asymptotic normality of
the -distance to the -distance for , and obtain the
analogous limiting result for a modification of the -distance for
. Since the -distance is the area between and ,
which is also the area between the inverse of and the more tractable
inverse of , the problem can be reduced immediately to
deriving asymptotic normality of the -distance between and .
Although we lose this easy correspondence for , we show that the
-distance between and is asymptotically equivalent to the
-distance between and .Comment: Published at http://dx.doi.org/10.1214/009053605000000462 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
On the upper limit of antinuclei content in cosmic rays
Upper limit of antinuclei content in cosmic ray
Magnetic degeneracy and hidden metallicity of the spin density wave state in ferropnictides
We analyze spin density wave (SDW) order in iron-based superconductors and
electronic structure in the SDW phase. We consider an itinerant model for
Fe-pnictides with two hole bands centered at and two electron bands
centered at and in the unfolded BZ. A SDW order in such a
model is generally a combination of two components with momenta and
, both yield order in the folded zone. Neutron
experiments, however, indicate that only one component is present. We show that
or order is selected if we assume that only one hole band
is involved in the SDW mixing with electron bands. A SDW order in such 3-band
model is highly degenerate for a perfect nesting and hole-electron interaction
only, but we show that ellipticity of electron pockets and interactions between
electron bands break the degeneracy and favor the desired or
order. We further show that stripe-ordered system remains a metal for
arbitrary coupling. We analyze electronic structure for parameters relevant to
the pnictides and argue that the resulting electronic structure is in good
agreement with ARPES experiments. We discuss the differences between our model
and model of localized spins.Comment: reference list updated, typos are correcte
Interplay between magnetism and superconductivity in Fe-pnictides
We consider phase transitions and potential co-existence of spin-density-wave
(SDW) magnetic order and extended s-wave () superconducting order within a
two-band itinerant model of iron pnictides, in which SDW magnetism and
superconductivity are competing orders. We show that depending on parameters,
the transition between these two states is either first order, or involves an
intermediate phase in which the two orders co-exist. We demonstrate that such
co-existence is possible when SDW order is incommensurate.Comment: 5 pages, 3 figure
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