2,543 research outputs found
Generators of simple modular Lie superalgebras
Let be one of the finite-dimensional simple graded Lie superalgebras of
Cartan type or over an algebraically closed
field of characteristic . In this paper we prove that can be generated
by one element except the ones of type , or in certain
exceptional cases, in which can be generated by two elements. As a
subsidiary result, we also prove that certain classical Lie superalgebras or
their relatives can be generated by one or two elements
Evaluating the use of covariance-based structural equation modelling with reflective measurement in organizational and management research : a review and recommendations for best practice
Covarianceâbased structural equation modelling (CBâSEM) with reflective measurement has been a popular data analysis tool in organizational and management research. Extensive studies and guidelines have been published on what constitutes its best practice. What is much less known is the extent to which CBâSEM users in organizational and management research comprehend and adhere to the standards and principles behind this advanced analytical technique. In this study, we first devised an evaluation scheme to assess the quality of CBâSEM performed in a study, and then utilized this scheme to examine 144 CBâSEM studies published in 12 top organizational and management journals between 2011 and 2016. The evaluation of the published studies revealed a pressing need for more systematic and standardized approaches to planning, conducting and reporting CBâSEM studies. We discussed the implication of the findings for future work
Methods to Expedite and Streamline Utility Relocations for Road Projects
Executive Summary This report describes best practices and tools to streamline and expedite utility relocations when they are required as part of road construction projects. As part of this effort, a research team from the Kentucky Transportation Center (KTC) conducted extensive qualitative research that involved mapping current practices at the Kentucky Transportation Cabinet (KYTC) and reviewing utility manuals from KYTC and other state transportation agencies. The KTC research team also conducted in-depth interviews with KYTC engineers and staff as well as representatives from utility companies (UCs). Based on the data from these investigations, KTC developed a number of recommendations to improve interactions between KYTC and UCs. A number of the proposed improvements relate to training and coordination. For instance, fostering better coordination between KYTC and UCs early in the design process can prevent unexpected delays from hampering the construction process, cut down on the impacts to utilities, and allow for the exploration of alternative design options to identify those that will minimize expense while optimizing efficiencies and shortening project duration. Preconstruction meetings facilitate improved communication between KYTC and UCs, and set the stage for holding follow-up meetings throughout the construction process. All of these suggestions will forge better communication and therefore lead to stronger coordination between the Cabinet and UCs. The research team organized the suggested practices according to use and benefit while also itemizing some of the drawbacks associated with using those respective practices. The guidance provided in this report will provide KYTC utility staff with the knowledge of best practices, while also informing them on the circumstances under which each should be implemented. To accompany the summary of best practices, KTC researchers developed a method of risk assessment to determine the level of difficulty a project may expect when utility relocations are necessary. This model, which uses multiple linear regression, has robust predictive utility (R2 = 0.84), and will offer KYTC staff insights into what best practices are most compatible with the level of risk faced. This study presents several valuable tools along with organized best practices and guidance for STAsâ utility coordinators. When used pragmatically, these methods will assist in STAs and UCs in identifying problematic projects early in their life to resolve any issues
Neutron matter at zero temperature with auxiliary field diffusion Monte Carlo
The recently developed auxiliary field diffusion Monte Carlo method is
applied to compute the equation of state and the compressibility of neutron
matter. By combining diffusion Monte Carlo for the spatial degrees of freedom
and auxiliary field Monte Carlo to separate the spin-isospin operators, quantum
Monte Carlo can be used to simulate the ground state of many nucleon systems
(A\alt 100). We use a path constraint to control the fermion sign problem. We
have made simulations for realistic interactions, which include tensor and
spin--orbit two--body potentials as well as three-nucleon forces. The Argonne
and two nucleon potentials plus the Urbana or Illinois
three-nucleon potentials have been used in our calculations. We compare with
fermion hypernetted chain results. We report results of a Periodic Box--FHNC
calculation, which is also used to estimate the finite size corrections to our
quantum Monte Carlo simulations. Our AFDMC results for models of pure
neutron matter are in reasonably good agreement with equivalent Correlated
Basis Function (CBF) calculations, providing energies per particle which are
slightly lower than the CBF ones. However, the inclusion of the spin--orbit
force leads to quite different results particularly at relatively high
densities. The resulting equation of state from AFDMC calculations is harder
than the one from previous Fermi hypernetted chain studies commonly used to
determine the neutron star structure.Comment: 15 pages, 15 tables and 5 figure
A local families index formula for d-bar operators on punctured Riemann surfaces
Using heat kernel methods developed by Vaillant, a local index formula is
obtained for families of d-bar operators on the Teichmuller universal curve of
Riemann surfaces of genus g with n punctures. The formula also holds on the
moduli space M{g,n} in the sense of orbifolds where it can be written in terms
of Mumford-Morita-Miller classes. The degree two part of the formula gives the
curvature of the corresponding determinant line bundle equipped with the
Quillen connection, a result originally obtained by Takhtajan and Zograf.Comment: 47 page
Invariant structure of the hierarchy theory of fractional quantum Hall states with spin
We describe the invariant structure common to abelian fractional quantum Hall
systems with spin. It appears in a generalization of the lattice description of
the polarized hierarchy that encompasses both partially polarized and
unpolarized ground state systems. We formulate, using the spin-charge
decomposition, conditions that should be satisfied so that the description is
SU(2) invariant. In the case of the spin- singlet hierarchy construction, we
find that there are as many SU(2) symmetries as there are levels in the
construction. We show the existence of a spin and charge lattice for the
systems with spin. The ``gluing'' of the charge and spin degrees of freedom in
their bulk is described by the gluing theory of lattices.Comment: 21 pages, LaTex, Submitted to Phys. Rev.
Effect of CO2 on the Processing of Y-Ba-Cu-O Superconductors
The superconducting properties of YBa2Cu3O6+x reacted with various known ratios of O2/CO2 gas mixtures during sintering at different temperatures were studied. Jc was found to decrease drastically upon reaction with CO2, becoming zero at certain CO2 activities. The stability region for the 123 superconductor, as a function of CO2 activity and temperature, was empirically formulated as follows: log pCO2 \u3c (â45,000)/T + 33.4. The grain boundaries in sintered samples with Jc = 0 were investigated with HRTEM in conjunction with EDS. Two distinct types of grain boundaries were observed. Approximately 10% of the grain boundaries were wet by a thin layer of a second phase, deduced to be BaCuO2. The remaining boundaries were sharp grain boundaries. The grain structure near the sharp grain boundaries was tetragonal. These two types of grain boundaries are thought to be responsible for Jc being zero
Role of fractal dimension in random walks on scale-free networks
Fractal dimension is central to understanding dynamical processes occurring
on networks; however, the relation between fractal dimension and random walks
on fractal scale-free networks has been rarely addressed, despite the fact that
such networks are ubiquitous in real-life world. In this paper, we study the
trapping problem on two families of networks. The first is deterministic, often
called -flowers; the other is random, which is a combination of
-flower and -flower and thus called hybrid networks. The two
network families display rich behavior as observed in various real systems, as
well as some unique topological properties not shared by other networks. We
derive analytically the average trapping time for random walks on both the
-flowers and the hybrid networks with an immobile trap positioned at an
initial node, i.e., a hub node with the highest degree in the networks. Based
on these analytical formulae, we show how the average trapping time scales with
the network size. Comparing the obtained results, we further uncover that
fractal dimension plays a decisive role in the behavior of average trapping
time on fractal scale-free networks, i.e., the average trapping time decreases
with an increasing fractal dimension.Comment: Definitive version published in European Physical Journal
A quasilocal calculation of tidal heating
We present a method for computing the flux of energy through a closed surface
containing a gravitating system. This method, which is based on the quasilocal
formalism of Brown and York, is illustrated by two applications: a calculation
of (i) the energy flux, via gravitational waves, through a surface near
infinity and (ii) the tidal heating in the local asymptotic frame of a body
interacting with an external tidal field. The second application represents the
first use of the quasilocal formalism to study a non-stationary spacetime and
shows how such methods can be used to study tidal effects in isolated
gravitating systems.Comment: REVTex, 4 pages, 1 typo fixed, standard sign convention adopted for
the Newtonian potential, a couple of lines added to the discussion of gauge
dependent term
A quantum analogue of the first fundamental theorem of invariant theory
We establish a noncommutative analogue of the first fundamental theorem of
classical invariant theory. For each quantum group associated with a classical
Lie algebra, we construct a noncommutative associative algebra whose underlying
vector space forms a module for the quantum group and whose algebraic structure
is preserved by the quantum group action. The subspace of invariants is shown
to form a subalgebra, which is finitely generated. We determine generators of
this subalgebra of invariants and determine their commutation relations. In
each case considered, the noncommutative modules we construct are flat
deformations of their classical commutative analogues. Thus by taking the limit
as , our results imply the first fundamental theorem of classical
invariant theory, and therefore generalise them to the noncommutative case.Comment: 44 pages, 3 figure
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