335 research outputs found
On the number of classes of conjugate Hall subgroups in finite simple groups
In this paper we find the number of conjugate -Hall subgroups in all
finite almost simple groups. We also complete the classification of -Hall
subgroups in finite simple groups and correct some mistakes from our previous
paper.Comment: article in press in "Journal of algebra
Instabilities in the two-dimensional cubic nonlinear Schrodinger equation
The two-dimensional cubic nonlinear Schrodinger equation (NLS) can be used as
a model of phenomena in physical systems ranging from waves on deep water to
pulses in optical fibers. In this paper, we establish that every
one-dimensional traveling wave solution of NLS with trivial phase is unstable
with respect to some infinitesimal perturbation with two-dimensional structure.
If the coefficients of the linear dispersion terms have the same sign then the
only unstable perturbations have transverse wavelength longer than a
well-defined cut-off. If the coefficients of the linear dispersion terms have
opposite signs, then there is no such cut-off and as the wavelength decreases,
the maximum growth rate approaches a well-defined limit.Comment: 4 pages, 4 figure
Unusual bound states of quark matter within the NJL model
Properties of dense quark matter in and out of chemical equilibrium are
studied within the SU(3) Nambu-Jona-Lasinio model. In addition to the 4-fermion
scalar and vector terms the model includes also the 6-fermion flavour mixing
interaction. First we study a novel form of deconfined matter, meso-matter,
which is composed of equal number of quarks and antiquarks. It can be thought
of as a strongly compressed meson gas where mesons are melted into their
elementary constituents, quarks and antiquarks. Strongly bound states in this
quark-antiquark matter are predicted for all flavour combinations of
quark-antiquark pairs. The maximum binding energy reaches up to 180 MeV per
pair for mixtures with about 70% of strange quark-antiquark pairs. Equilibrated
baryon-rich quark matter with various flavour compositions is also studied. In
this case only shallow bound states appear in systems with a significant
admixture (about 40%) of strange quarks (strangelets). Their binding energies
are quite sensitive to the relative strengths of scalar and vector
interactions. The common property of all these bound states is that they appear
at high particle densities when the chiral symmetry is nearly restored. Thermal
properties of meso-matter as well as chemically equilibrated strange quark
matter are also investigated. Possible decay modes of these bound states are
discussed.Comment: 26 pages, 16 PostScript figures, RevTe
A Symmetry-induced Model of Elliptical Galaxy Patterns
S\'ersic (1968) generalized the de Vaucouleurs law which follows the
projected (observed) one dimensional radial profile of elliptical galaxies
closely and Dehnen (1993) proposed an analytical formula of the 3-dimensional
light distributions whose projected line profile resembles the de Vaucouleurs
law. This paper is involved to recover the Dehnen model and generalize the
model to account for galaxy elliptical shapes by means of curvilinear
coordinate systems and employing a symmetry principle. The symmetry principle
maps an orthogonal coordinate system to a light distribution pattern. The
coordinate system for elliptical galaxy patterns turns out to be the one which
is formed by the complex-plane reciprocal transformation . The resulting
spatial (3-dimensional) light distribution is spherically symmetric and has
infinite gradient at its centre, which is called spherical-nucleus solution and
is used to model galaxy central area. We can make changes of the coordinate
system by cutting out some column areas of its definition domain, the areas
containing the galaxy centre. The resulting spatial (3-dimensional) light
distributions are axisymmetric or triaxial and have zero gradient at the
centre, which are called elliptical-shape solutions and are used to model
global elliptical patterns. The two types of logarithmic light distributions
are added together to model full elliptical galaxy patterns. The model is a
generalization of the Dehnen model. One of the elliptical-shape solutions
permits realistic numerical calculation and is fitted to all R-band elliptical
images from the Frei {\it et al.}(1996)'s galaxy sample. The fitting is
satisfactory. This suggests that elliptical galaxy patterns can be represented
in terms of a few basic parameters.Comment: 20 pages, 7 figure
New games, new rules: big data and the changing context of strategy
Big data and the mechanisms by which it is produced and disseminated introduce important changes in the ways information is generated and made relevant for organizations. Big data often represents miscellaneous records of the whereabouts of large and shifting online crowds. It is frequently agnostic, in the sense of being produced for generic purposes or purposes different from those sought by big data crunching. It is based on varying formats and modes of communication (e.g., texts, image and sound), raising severe problems of semiotic translation and meaning compatibility. Crucially, the usefulness of big data rests on their steady updatability, a condition that reduces the time span within which this data is useful or relevant. Jointly, these attributes challenge established rules of strategy making as these are manifested in the canons of procuring structured information of lasting value that addresses specific and long-term organizational objectives. The developments underlying big data thus seem to carry important implications for strategy making, and the data and information practices with which strategy has been associated. We conclude by placing the understanding of these changes within the wider social and institutional context of longstanding data practices and the significance they carry for management and organizations
Body weight-length relationships in giant otters (Pteronura brasiliensis) (Carnivora, Mustelidae)
Few giant otters (Pteronura brasiliensis) have been measured and weighed and its actual size is controversial in the literature. This study presents the weight-length relationship of Amazonian giant otters using 15 captive individuals. The maximum length and weight were 163cm and 22.5kg, and 162cm and 28.8kg, for the males and females, respectively. The weight-length relationships were not significantly different between the sexes (t = 0.658, d.f.=11, P>0.05) and can be expressed by the equation: W=1.48Ă10-5 L2.81. Considering that some of the giant otters used in this study were old individuals (more than 10 years old), and that all the animals analyzed were healthy, it is possible to assume that the weight-length relationships obtained are probably a close approximation of the relationship of giant otters of the Amazon region and can be used by institutions that keep this species in captivity as a base to quickly assess the animal's nutritive status. © 2009 Tecpar
Gaussian quantum operator representation for bosons
We introduce a Gaussian quantum operator representation, using the most general possible multimode Gaussian operator basis. The representation unifies and substantially extends existing phase-space representations of density matrices for Bose systems and also includes generalized squeezed-state and thermal bases. It enables first-principles dynamical or equilibrium calculations in quantum many-body systems, with quantum uncertainties appearing as dynamical objects. Any quadratic Liouville equation for the density operator results in a purely deterministic time evolution. Any cubic or quartic master equation can be treated using stochastic methods
The Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a second generation water Cherenkov
detector designed to determine whether the currently observed solar neutrino
deficit is a result of neutrino oscillations. The detector is unique in its use
of D2O as a detection medium, permitting it to make a solar model-independent
test of the neutrino oscillation hypothesis by comparison of the charged- and
neutral-current interaction rates. In this paper the physical properties,
construction, and preliminary operation of the Sudbury Neutrino Observatory are
described. Data and predicted operating parameters are provided whenever
possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and
epsf style files. For additional information about SNO see
http://www.sno.phy.queensu.ca . This version has some new reference
Measurement of the View the tt production cross-section using eÎŒ events with b-tagged jets in pp collisions at âs = 13 TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (ÏttÂŻ) with a data sample of 3.2 fbâ1 of protonâproton collisions at a centre-of-mass energy of âs = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electronâmuon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously ÏttÂŻ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:
ÏttÂŻ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb,
where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
- âŠ