2,239 research outputs found
Survival, Breeding Frequency, and Migratory Orientation in the Jefferson Salamander, \u3ci\u3eAmbystoma Jeffersonianum\u3c/i\u3e
Accurate estimates of demographic parameters, such as survival and breeding frequency, are necessary for the conservation and management of animal populations. Additionally, life-history data are required for gaining an empirical understanding of the ecology of natural populations. We monitored a population of Jefferson Salamanders (Ambystoma jeffersonianum) breeding in a permanent mountain-top pond at the southern limit of this species’ geographic range in Virginia over four years. We used closed multistate mark-recapture models with Pollock\u27s robust design to estimate the demographic parameters of this population. Additionally, we used point-of-capture data to compare the orientation of migrations into and out of the pond within and among years. Our model selection results support consistent annual adult survival across years with higher estimates for males compared to females. Our estimates of the probability of breeding in sequential years were high for both sexes during the four years of our study. Our model rankings and capture probability estimates indicate that females had a higher probability of detection when entering the breeding pond, likely reflecting differences between the sexes in arrival time to the pond. We found directionality in some, but not all, annual migrations, despite indications of individual fidelity in orientation across years. Our study provides the first estimates of breeding probability and assessment of migratory orientation patterns for A. jeffersonianum and contributes to the understanding of the reproductive ecology and natural history of pond-breeding amphibians
The Casas-Alvero conjecture for infinitely many degrees
Over a field of characteristic zero, it is clear that a polynomial of the
form (X-a)^d has a non-trivial common factor with each of its d-1 first
derivatives. The converse has been conjectured by Casas-Alvero. Up to now there
have only been some computational verifications for small degrees d. In this
paper the conjecture is proved in the case where the degree of the polynomial
is a power of a prime number, or twice such a power.
Moreover, for each positive characteristic p, we give an example of a
polynomial of degree d which is not a dth power but which has a common factor
with each of its first d-1 derivatives. This shows that the assumption of
characteristic zero is essential for the converse statement to hold.Comment: 7 pages; v2: corrected some typos and references, and added section
on computational aspect
STRINGVACUA: A Mathematica Package for Studying Vacuum Configurations in String Phenomenology
We give a simple tutorial introduction to the Mathematica package
STRINGVACUA, which is designed to find vacua of string-derived or inspired
four-dimensional N=1 supergravities. The package uses powerful
algebro-geometric methods, as implemented in the free computer algebra system
Singular, but requires no knowledge of the mathematics upon which it is based.
A series of easy-to-use Mathematica modules are provided which can be used both
in string theory and in more general applications requiring fast polynomial
computations. The use of these modules is illustrated throughout with simple
examples.Comment: 21 pages, 9 figure
Tropical types and associated cellular resolutions
An arrangement of finitely many tropical hyperplanes in the tropical torus
leads to a notion of `type' data for points, with the underlying unlabeled
arrangement giving rise to `coarse type'. It is shown that the decomposition of
the tropical torus induced by types gives rise to minimal cocellular
resolutions of certain associated monomial ideals. Via the Cayley trick from
geometric combinatorics this also yields cellular resolutions supported on
mixed subdivisions of dilated simplices, extending previously known
constructions. Moreover, the methods developed lead to an algebraic algorithm
for computing the facial structure of arbitrary tropical complexes from point
data.Comment: minor correction
Products of Borel fixed ideals of maximal minors
We study a large family of products of Borel fixed ideals of maximal minors.
We compute their initial ideals and primary decompositions, and show that they
have linear free resolutions. The main tools are an extension of straightening
law and a very surprising primary decomposition formula. We study also the
homological properties of associated multi-Rees algebra which are shown to be
Cohen-Macaulay, Koszul and defined by a Gr\"obner basis of quadrics
Reconstruction of Fractional Quantum Hall Edges
We study the interplay of interaction, confining potential and effects of
finite temperature at the edge of a quantum Hall liquid. Our exact
diagonalization calculation indicates that edge reconstruction occurs in the
fractional quantum Hall regime for a variety of confining potential, including
ones that correspond to a "sharp" edge. Our finite temperature Hartree-Fock
calculation for integer quantum Hall edges indicates that reconstruction is
suppressed above certain temperature. We discuss the implication of our results
on recent edge tunneling and microwave absorption experiments.Comment: Revised version. 5 papges RevTex with 5 eps figures embedded in the
tex
Umklapp scattering at reconstructed quantum-Hall edges
We study the low-lying excitations of a quantum-Hall sample that has
undergone edge reconstruction such that there exist three branches of chiral
edge excitations. Among the interaction processes that involve electrons close
to the three Fermi points is a new type of Umklapp-scattering process which has
not been discussed before. Using bosonization and a refermionization technique,
we obtain exact results for electronic correlation functions and discuss the
effect Umklapp scattering has on the Luttinger-liquid properties of
quantum-Hall edges.Comment: 4 pages, 1 figure, uses elsart.cls and phbauth.cls (both are
included), contribution to EP2DS-13, to be published in Physica
A New Method for Finding Vacua in String Phenomenology
One of the central problems of string-phenomenology is to find stable vacua
in the four dimensional effective theories which result from compactification.
We present an algorithmic method to find all of the vacua of any given
string-phenomenological system in a huge class. In particular, this paper
reviews and then extends hep-th/0606122 to include various non-perturbative
effects. These include gaugino condensation and instantonic contributions to
the superpotential.Comment: 27 pages, 5 .eps figures. V2: Minor corrections, reference adde
Eigenvectors of tensors and algorithms for Waring decomposition
A Waring decomposition of a (homogeneous) polynomial f is a minimal sum of
powers of linear forms expressing f. Under certain conditions, such a
decomposition is unique. We discuss some algorithms to compute the Waring
decomposition, which are linked to the equation of certain secant varieties and
to eigenvectors of tensors. In particular we explicitly decompose a general
cubic polynomial in three variables as the sum of five cubes (Sylvester
Pentahedral Theorem).Comment: 32 pages; three Macaulay2 files as ancillary files. Revised with
referee's suggestions. Accepted JS
ColMix -- A Simple Data Augmentation Framework to Improve Object Detector Performance and Robustness in Aerial Images
In the last decade, Convolutional Neural Network (CNN) and transformer based
object detectors have achieved high performance on a large variety of datasets.
Though the majority of detection literature has developed this capability on
datasets such as MS COCO, these detectors have still proven effective for
remote sensing applications. Challenges in this particular domain, such as
small numbers of annotated objects and low object density, hinder overall
performance. In this work, we present a novel augmentation method, called
collage pasting, for increasing the object density without a need for
segmentation masks, thereby improving the detector performance. We demonstrate
that collage pasting improves precision and recall beyond related methods, such
as mosaic augmentation, and enables greater control of object density. However,
we find that collage pasting is vulnerable to certain out-of-distribution
shifts, such as image corruptions. To address this, we introduce two simple
approaches for combining collage pasting with PixMix augmentation method, and
refer to our combined techniques as ColMix. Through extensive experiments, we
show that employing ColMix results in detectors with superior performance on
aerial imagery datasets and robust to various corruptions
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