7,462 research outputs found
Outer crust of a cold non-accreting magnetar
The outer crust structure and composition of a cold, non-accreting magnetar
is studied. We model the outer crust to be made of fully equilibrated matter
where ionized nuclei form a Coulomb crystal embedded in an electron gas. The
main effects of the strong magnetic field are those of quantizing the electron
motion in Landau levels and of modifying the nuclear single particle levels
producing, on average, an increased binding of nucleons in nuclei present in
the Coulomb lattice. The effect of an homogeneous and constant magnetic field
on nuclear masses has been predicted by using a covariant density functional,
in which induced currents and axial deformation due to the presence of a
magnetic field that breaks time-reversal symmetry have been included
self-consistently in the nucleon and meson equations of motion. Although not
yet observed, for G both effects contribute to produce
different compositions and to enlarge the range of pressures typically present
in common neutron stars. Specifically, in such a regime, the magnetic field
effects on nuclei favor the appearance of heavier nuclei at low pressures. As
increases, such heavier nuclei are also preferred up to larger pressures.
In the most extreme case, the whole outer crust is almost made of
Zr.Comment: Published versio
Power-enhanced multiple decision functions controlling family-wise error and false discovery rates
Improved procedures, in terms of smaller missed discovery rates (MDR), for
performing multiple hypotheses testing with weak and strong control of the
family-wise error rate (FWER) or the false discovery rate (FDR) are developed
and studied. The improvement over existing procedures such as the \v{S}id\'ak
procedure for FWER control and the Benjamini--Hochberg (BH) procedure for FDR
control is achieved by exploiting possible differences in the powers of the
individual tests. Results signal the need to take into account the powers of
the individual tests and to have multiple hypotheses decision functions which
are not limited to simply using the individual -values, as is the case, for
example, with the \v{S}id\'ak, Bonferroni, or BH procedures. They also enhance
understanding of the role of the powers of individual tests, or more precisely
the receiver operating characteristic (ROC) functions of decision processes, in
the search for better multiple hypotheses testing procedures. A
decision-theoretic framework is utilized, and through auxiliary randomizers the
procedures could be used with discrete or mixed-type data or with rank-based
nonparametric tests. This is in contrast to existing -value based procedures
whose theoretical validity is contingent on each of these -value statistics
being stochastically equal to or greater than a standard uniform variable under
the null hypothesis. Proposed procedures are relevant in the analysis of
high-dimensional "large , small " data sets arising in the natural,
physical, medical, economic and social sciences, whose generation and creation
is accelerated by advances in high-throughput technology, notably, but not
limited to, microarray technology.Comment: Published in at http://dx.doi.org/10.1214/10-AOS844 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
A formula for charmonium suppression
In this work a formula for charmonium suppression obtained by Matsui in 1989
is analytically generalized for the case of complex c-cbar potential described
by a 3-dimensional and isotropic time-dependent harmonic oscillator (THO). It
is suggested that under certain conditions the formula can be applied to
describe J/\psi suppression in heavy-ion collisions at CERN-SPS, RHIC, and LHC
with the advantage of analytical tractability.Comment: 4 pages, no figures, to appear in Phys. At. Nucl., vol. 7
Description of nuclear systems with a self-consistent configuration-mixing approach. I: Theory, algorithm, and application to the C test nucleus
Although self-consistent multi-configuration methods have been used for
decades to address the description of atomic and molecular many-body systems,
only a few trials have been made in the context of nuclear structure. This work
aims at the development of such an approach to describe in a unified way
various types of correlations in nuclei, in a self-consistent manner where the
mean-field is improved as correlations are introduced. The goal is to reconcile
the usually set apart Shell-Model and Self-Consistent Mean-Field methods. This
approach is referred as "variational multiparticle-multihole configuration
mixing method". It is based on a double variational principle which yields a
set of two coupled equations that determine at the same time the expansion
coefficients of the many-body wave function and the single particle states. The
formalism is derived and discussed in a general context, starting from a
three-body Hamiltonian. Links to existing many-body techniques such as the
formalism of Green's functions are established. First applications are done
using the two-body D1S Gogny effective force. The numerical procedure is tested
on the C nucleus in order to study the convergence features of the
algorithm in different contexts. Ground state properties as well as
single-particle quantities are analyzed, and the description of the first
state is examined. This study allows to validate our numerical algorithm and
leads to encouraging results. In order to test the method further, we will
realize in the second article of this series, a systematic description of more
nuclei and observables obtained by applying the newly-developed numerical
procedure with the same Gogny force. As raised in the present work,
applications of the variational multiparticle-multihole configuration mixing
method will however ultimately require the use of an extended and more
constrained Gogny force.Comment: 22 pages, 18 figures, accepted for publication in Phys. Rev. C. v2:
minor corrections and references adde
Analysis of Fantasy Fiction Series of Sarah J. Maas: A Court of Thorns and Roses
This thesis offers a feminist interpretation of A Court of Thorns and Roses, a series by Sarah J. Maas. The fantasy fiction series began publication in 2015 and released its companion book in 2018. Protagonist Feyre navigates values about femininity and masculinity, breaking standards, as she develops throughout the series to change the fae and human worlds. Feyre stands up to inequality and helps others, both human and fae, to make peace instead of war. This analysis uncovers the gender roles, literary elements, and fairy tale influences on the series A Court of Thorns and Roses. Prominent symbolism involves masks, hands, and wounds. Feyre’s new powers as High Fae have parallels with gender issues, such as how the ability to shapeshift is like her ability to shift between and to combine the masculine and feminine spheres. Through Feyre’s experiences and transformation from human to fae, Maas shows a heightened version of social issues that many young adults face, thus providing readers with assurance that their responses to trauma are valid. Filling a gap in literary scholarship about contemporary young adult literature, this thesis demonstrates the value of analyzing popular literature such as the works of Sarah J. Maas
High-performance functional renormalization group calculations for interacting fermions
We derive a novel computational scheme for functional Renormalization Group
(fRG) calculations for interacting fermions on 2D lattices. The scheme is based
on the exchange parametrization fRG for the two-fermion interaction, with
additional insertions of truncated partitions of unity. These insertions
decouple the fermionic propagators from the exchange propagators and lead to a
separation of the underlying equations. We demonstrate that this separation is
numerically advantageous and may pave the way for refined, large-scale
computational investigations even in the case of complex multiband systems.
Furthermore, on the basis of speedup data gained from our implementation, it is
shown that this new variant facilitates efficient calculations on a large
number of multi-core CPUs. We apply the scheme to the , Hubbard model on
a square lattice to analyze the convergence of the results with the bond length
of the truncation of the partition of unity. In most parameter areas, a fast
convergence can be observed. Finally, we compare to previous results in order
to relate our approach to other fRG studies.Comment: 26 pages, 9 figure
Outlier Detection Using Nonconvex Penalized Regression
This paper studies the outlier detection problem from the point of view of
penalized regressions. Our regression model adds one mean shift parameter for
each of the data points. We then apply a regularization favoring a sparse
vector of mean shift parameters. The usual penalty yields a convex
criterion, but we find that it fails to deliver a robust estimator. The
penalty corresponds to soft thresholding. We introduce a thresholding (denoted
by ) based iterative procedure for outlier detection (-IPOD). A
version based on hard thresholding correctly identifies outliers on some hard
test problems. We find that -IPOD is much faster than iteratively
reweighted least squares for large data because each iteration costs at most
(and sometimes much less) avoiding an least squares estimate.
We describe the connection between -IPOD and -estimators. Our
proposed method has one tuning parameter with which to both identify outliers
and estimate regression coefficients. A data-dependent choice can be made based
on BIC. The tuned -IPOD shows outstanding performance in identifying
outliers in various situations in comparison to other existing approaches. This
methodology extends to high-dimensional modeling with , if both the
coefficient vector and the outlier pattern are sparse
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