5,857 research outputs found
Objective functions with redundant domains
Let (E,A) be a set system consisting of a finite collection A of subsets of a ground set E, and suppose that we have a function Ï which maps A into some set S. Now removing a subset K from E gives a restriction A(KÂŻ) to those sets of A disjoint from K, and we have a corresponding restriction Ï|A(KÂŻ) of our function Ï. If the removal of K does not affect the image set of Ï, that is Im(Ï|A(XÂŻ))=Im(Ï), then we will say that K is a kernel set of A with respect to Ï. Such sets are potentially useful in optimisation problems defined in terms of Ï. We will call the set of all subsets of E that are kernel sets with respect to Ï a kernel system and denote it by KerÏ(A). Motivated by the optimisation theme, we ask which kernel systems are matroids. For instance, if A is the collection of forests in a graph G with coloured edges and Ï counts how many edges of each colour occurs in a forest then KerÏ(A) is isomorphic to the disjoint sum of the cocycle matroids of the differently coloured subgraphs; on the other hand, if A is the power set of a set of positive integers, and Ï is the function which takes the values 1 and 0 on subsets according to whether they are sum-free or not, then we show that KerÏ(A) is essentially never a matroid
Property Assessments and Information Asymmetry in Residential Real Estate
This paper presents a game theoretic model of property tax assessment that allows a tax appraiser to either choose a high or a low assessment. The owner either accepts or challenges this assessment. A ââfixed effectsââ regression model is used to evaluate the differences in the assessed values of a sample of houses from Bexar County, Texas during 2000 and 2001. Where the owner of the house is identified as a state licensed property tax consultant, the assessed value, after adjusting for size, age, and other economic characteristics, ranged from a statistically robust 2.5% to 6.2% lower than neighboring houses.
Doppler cooling of gallium atoms: 2. Simulation in complex multilevel systems
This paper derives a general procedure for the numerical solution of the
Lindblad equations that govern the coherences arising from multicoloured light
interacting with a multilevel system. A systematic approach to finding the
conservative and dissipative terms is derived and applied to the laser cooling
of gallium. An improved numerical method is developed to solve the
time-dependent master equation and results are presented for transient cooling
processes. The method is significantly more robust, efficient and accurate than
the standard method and can be applied to a broad range of atomic and molecular
systems. Radiation pressure forces and the formation of dynamic dark-states are
studied in the gallium isotope 66Ga.Comment: 15 pages, 8 figure
Implicit Liquidity Premiums in the Disposition of RTC Assets
The Resolution Trust Corporation (RTC) was created by congressional legislation passed in 1989, and was charged with, among other things, the orderly disposition of other real estate owned (OREO) property. Questions have been raised about how efficient and effective the RTC has been in achieved its congressional mandate. One of the issues resulting from the efficiency question involves the amount of discount the RTC realizes for a quick disposition of the property. This study utilizes data provided by the RTC concerning its sales to analyze the implicit liquidity premium resulting from disposing of OREO. The results of the study indicate what variables contribute to liquidity premiums. This paper's importance relies most heavily on the finding that realistic market adjustments in regulation, over time, helped to achieve a higher degree of liquidity for RTC real estate property sales. The findings of this paper confirm the legislative intent of FIRREA, which is to ensure that real estate properties acquired by the government are disposed of at the highest dollar value possible.
Sampling a Littoral Fish Assemblage: Comparison of Small-Mesh Fyke Netting and Boat Electrofishing
We compared small-mesh (4-mm) fyke netting and boat electrofishing for sampling a littoral fish assemblage in Muskegon Lake, Michigan. We hypothesized that fyke netting selects for small-bodied fishes and electrofishing selects for large-bodied fishes. Three sites were sampled during May (2004 and 2005), July (2005 only), and September (2004 and 2005). We found that the species composition of captured fish differed considerably between fyke netting and electrofishing based on nonmetric multidimensional scaling (NMDS). Species strongly associated with fyke netting (based on NMDS and relative abundance) included the brook silverside Labidesthes sicculus, banded killifish Fundulus diaphanus, round goby Neogobius melanostomus, mimic shiner Notropis volucellus, and bluntnose minnow Pimephales notatus, whereas species associated with electrofishing included the Chinook salmon Oncorhynchus tshawytscha, catostomids (Moxostoma spp. and Catostomus spp.), freshwater drum Aplodinotus grunniens, walleye Sander vitreus, gizzard shad Dorosoma cepedianum, and common carp Cyprinus carpio. The total length of fish captured by electrofishing was 12.8 cm (95% confidence interval ÂŒ 5.5â 17.2 cm) greater than that of fish captured by fyke netting. Size selectivity of the gears contributed to differences in species composition of the fish captured, supporting our initial hypothesis. Thus, small-mesh fyke nets and boat electrofishers provided complementary information on a littoral fish assemblage. Our results support use of multiple gear types in monitoring and research surveys of fish assemblages.
Copyright by the American Fisheries Society 2007, Originally published in the North American Journal of Fisheries Management 27: 825-831, 2007
Searching for keV Sterile Neutrino Dark Matter with X-ray Microcalorimeter Sounding Rockets
High-resolution X-ray spectrometers onboard suborbital sounding rockets can
search for dark matter candidates that produce X-ray lines, such as decaying
keV-scale sterile neutrinos. Even with exposure times and effective areas far
smaller than XMM-Newton and Chandra observations, high-resolution, wide
field-of-view observations with sounding rockets have competitive sensitivity
to decaying sterile neutrinos. We analyze a subset of the 2011 observation by
the X-ray Quantum Calorimeter instrument centered on Galactic coordinates l =
165, b = -5 with an effective exposure of 106 seconds, obtaining a limit on the
sterile neutrino mixing angle of sin^2(2 theta) < 7.2e-10 at 95% CL for a 7 keV
neutrino. Better sensitivity at the level of sin^2(2 theta) ~ 2.1e-11 at 95\%
CL for a 7 keV neutrino is achievable with future 300-second observations of
the galactic center by the Micro-X instrument, providing a definitive test of
the sterile neutrino interpretation of the reported 3.56 keV excess from galaxy
clusters.Comment: 13 pages, 13 figures, submitted to Ap
Folding model analysis of alpha radioactivity
Radioactive decay of nuclei via emission of particles has been
studied theoretically in the framework of a superasymmetric fission model using
the double folding (DF) procedure for obtaining the -nucleus
interaction potential. The DF nuclear potential has been obtained by folding in
the density distribution functions of the nucleus and the daughter
nucleus with a realistic effective interaction. The M3Y effective interaction
has been used for calculating the nuclear interaction potential which has been
supplemented by a zero-range pseudo-potential for exchange along with the
density dependence. The nuclear microscopic -nucleus potential thus
obtained has been used along with the Coulomb interaction potential to
calculate the action integral within the WKB approximation. This subsequently
yields microscopic calculations for the half lives of decays of
nuclei. The density dependence and the exchange effects have not been found to
be very significant. These calculations provide reasonable estimates for the
lifetimes of radioactivity of nuclei.Comment: 7 pages including 1 figur
Light Hadron Masses from Lattice QCD
This article reviews lattice QCD results for the light hadron spectrum. We
give an overview of different formulations of lattice QCD, with discussions on
the fermion doubling problem and improvement programs. We summarize recent
developments in algorithms and analysis techniques, that render calculations
with light, dynamical quarks feasible on present day computer resources.
Finally, we summarize spectrum results for ground state hadrons and resonances
using various actions.Comment: 53 pages, 24 figures, one table; Rev.Mod.Phys. (published version);
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