2,204 research outputs found
Strong lens search in the ESO public Survey KiDS
We have started a systematic search of strong lens candidates in the ESO
public survey KiDS based on the visual inspection of massive galaxies in the
redshift range . As a pilot program we have inspected 100 sq. deg.,
which overlap with SDSS and where there are known lenses to use as a control
sample. Taking advantage of the superb image quality of VST/OmegaCAM, the
colour information and accurate model subtracted images, we have found 18 new
lens candidates, for which spectroscopic confirmation will be needed to confirm
their lensing nature and study the mass profile of the lensing galaxies.Comment: 4 pages, 1 figure, to appear on the refereed Proceeding of the "The
Universe of Digital Sky Surveys" conference held at the INAF--OAC, Naples, on
25th-28th november 2014, to be published on Astrophysics and Space Science
Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodic
Voltage security evaluation based on perturbation method
This is the post-print version of the final paper published in International Journal of Electrical Power & Energy Systems. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2009 Elsevier B.V.This paper proposes a new algorithm for estimating voltage security margin. The algorithm is based on the perturbation method and has significant computational efficiency. The proposed algorithm can be used for on-line voltage security evaluation. It has been validated using IEEE-14, IEEE-30 and IEEE-57 bus systems. Results from the tests show higher efficiency and smaller error margins compared to continuation power flow (CPF) method.
Voltage collapse is a serious threat to the security of stressed power systems; therefore, voltage security (VS) has become a major challenge for management of power systems. The motivation for this research is a direct consequence of the deregulation of electricity industries and markets worldwide
Bicategories for boundary conditions and for surface defects in 3-d TFT
We analyze topological boundary conditions and topological surface defects in
three-dimensional topological field theories of Reshetikhin-Turaev type based
on arbitrary modular tensor categories. Boundary conditions are described by
central functors that lift to trivializations in the Witt group of modular
tensor categories. The bicategory of boundary conditions can be described
through the bicategory of module categories over any such trivialization. A
similar description is obtained for topological surface defects. Using string
diagrams for bicategories we also establish a precise relation between special
symmetric Frobenius algebras and Wilson lines involving special defects. We
compare our results with previous work of Kapustin-Saulina and of Kitaev-Kong
on boundary conditions and surface defects in abelian Chern-Simons theories and
in Turaev-Viro type TFTs, respectively.Comment: 34 pages, some figures. v2: references added. v3: typos corrected and
biliography update
From Zwiebach invariants to Getzler relation
We introduce the notion of Zwiebach invariants that generalize Gromov-Witten
invariants and homotopical algebra structures. We outline the induction
procedure that induces the structure of Zwiebach on the subbicomplex, that
gives the structure of Gromov-Witten invariants on subbicomplex with zero
diffferentials. We propose to treat Hodge dGBV with 1/12 axiom as the simplest
set of Zwiebach invariants, and explicitely prove that it induces WDVV and
Getzler equations in genera 0 and 1 respectively.Comment: 35 page
Spiders for rank 2 Lie algebras
A spider is an axiomatization of the representation theory of a group,
quantum group, Lie algebra, or other group or group-like object. We define
certain combinatorial spiders by generators and relations that are isomorphic
to the representation theories of the three rank two simple Lie algebras,
namely A2, B2, and G2. They generalize the widely-used Temperley-Lieb spider
for A1. Among other things, they yield bases for invariant spaces which are
probably related to Lusztig's canonical bases, and they are useful for
computing quantities such as generalized 6j-symbols and quantum link
invariants.Comment: 33 pages. Has color figure
A lower limit on the dark particle mass from dSphs
We use dwarf spheroidal galaxies as a tool to attempt to put precise lower
limits on the mass of the dark matter particle, assuming it is a sterile
neutrino. We begin by making cored dark halo fits to the line of sight velocity
dispersions as a function of projected radius (taken from Walker et al. 2007)
for six of the Milky Way's dwarf spheroidal galaxies. We test Osipkov-Merritt
velocity anisotropy profiles, but find that no benefit is gained over constant
velocity anisotropy. In contrast to previous attempts, we do not assume any
relation between the stellar velocity dispersions and the dark matter ones, but
instead we solve directly for the sterile neutrino velocity dispersion at all
radii by using the equation of state for a partially degenerate neutrino gas
(which ensures hydrostatic equilibrium of the sterile neutrino halo). This
yields a 1:1 relation between the sterile neutrino density and velocity
dispersion, and therefore gives us an accurate estimate of the Tremaine-Gunn
limit at all radii. By varying the sterile neutrino particle mass, we locate
the minimum mass for all six dwarf spheroidals such that the Tremaine-Gunn
limit is not exceeded at any radius (in particular at the centre). We find
sizeable differences between the ranges of feasible sterile neutrino particle
mass for each dwarf, but interestingly there exists a small range 270-280eV
which is consistent with all dSphs at the 1- level.Comment: 13 pages, 2 figures, 1 tabl
Character Expansion Methods for Matrix Models of Dually Weighted Graphs
We consider generalized one-matrix models in which external fields allow
control over the coordination numbers on both the original and dual lattices.
We rederive in a simple fashion a character expansion formula for these models
originally due to Itzykson and Di Francesco, and then demonstrate how to take
the large N limit of this expansion. The relationship to the usual matrix model
resolvent is elucidated. Our methods give as a by-product an extremely simple
derivation of the Migdal integral equation describing the large limit of
the Itzykson-Zuber formula. We illustrate and check our methods by analyzing a
number of models solvable by traditional means. We then proceed to solve a new
model: a sum over planar graphs possessing even coordination numbers on both
the original and the dual lattice. We conclude by formulating equations for the
case of arbitrary sets of even, self-dual coupling constants. This opens the
way for studying the deep problem of phase transitions from random to flat
lattices.Comment: 22 pages, harvmac.tex, pictex.tex. All diagrams written directly into
the text in Pictex commands. (Two minor math typos corrected.
Acknowledgements added.
Cubic String Field Theory in pp-wave Background and Background Independent Moyal Structure
We study Witten open string field theory in the pp-wave background in the
tensionless limit, and construct the N-string vertex in the basis which
diagonalizes the string perturbative spectrum. We found that the Witten
*-product can be viewed as infinite copies of the Moyal product with the same
noncommutativity parameter . Moreover, we show that this Moyal
structure is universal in the sense that, written in the string bit basis,
Witten's *-product for any background can always be given in terms of the
above-mentioned Moyal structure. We identify some projective operators in this
algebra that we argue to correspond to D-branes of the theory.Comment: Latex, 23 pages, reference adde
Computerized Adjudication of Coronary Heart Disease Events Using the Electronic Medical Record in HIV Clinical Research: Possibilities and Challenges Ahead
This pilot study assessed feasibility of computer-assisted electronic medical record (EMR) abstraction to ascertain coronary heart disease (CHD) event hospitalizations. We included a sample of 87 hospitalization records from participants the University of North Carolina (UNC) site of the Women's Interagency HIV Study (WIHS) and UNC Center for AIDS Research (CFAR) HIV Clinical Cohort who were hospitalized within UNC Healthcare System from July 2004 to July 2015. We compared a computer algorithm utilizing diagnosis/procedure codes, medications, and cardiac enzyme levels to adjudicate CHD events [myocardial infarction (MI)/coronary revascularization] from the EMR to standardized manual chart adjudication. Of 87 hospitalizations, 42 were classified as definite, 25 probable, and 20 non-CHD events by manual chart adjudication. A computer algorithm requiring presence of ≥1 CHD-related International Classification of Diseases, 9th Revision (ICD-9)/Current Procedural Terminology (CPT) code correctly identified 24 of 42 definite (57%), 29 of 67 probable/definite CHD (43%), and 95% of non-CHD events; additionally requiring clinically defined cardiac enzyme levels or administration of MI-related medications correctly identified 55%, 42%, and 95% of such events, respectively. Requiring any one of the ICD-9/CPT or cardiac enzyme criteria correctly identified 98% of definite, 97% of probable/definite CHD, and 85% of non-CHD events. Challenges included difficulty matching hospitalization dates, incomplete diagnosis code data, and multiple field names/locations of laboratory/medication data. Computer algorithms comprising only ICD-9/CPT codes failed to identify a sizable proportion of CHD events. Using a less restrictive algorithm yielded fewer missed events but increased the false-positive rate. Despite potential benefits of EMR-based research, there remain several challenges to fully computerized adjudication of CHD events
Superconducting zero temperature phase transition in two dimensions and in the magnetic field
We derive the Ginzburg-Landau-Wilson theory for the superconducting phase
transition in two dimensions and in the magnetic field. Without disorder the
theory describes a fluctuation induced first-order quantum phase transition
into the Abrikosov lattice. We propose a phenomenological criterion for
determining the transition field and discuss the qualitative effects of
disorder. Comparison with recent experiments on MoGe films is discussed.Comment: 7 pages, 2 figure
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