977 research outputs found
Simulations of Alice Electrodynamics on a Lattice
In this paper we present results of numerical simulations and some
(analytical) approximations of a compact U(1)\ltimes\ZZ_2 lattice gauge
theory, including an extra bare mass term for Alice fluxes. The subtle
interplay between Alice fluxes and (Cheshire) magnetic charges is analysed. We
determine the phase diagram and some characteristics of the model in three and
four dimensions. The results of the numerical simulations in various regimes,
compare well with some analytic approximations.Comment: 17 pages, 16 figures; minor change
Askey-Wilson Type Functions, With Bound States
The two linearly independent solutions of the three-term recurrence relation
of the associated Askey-Wilson polynomials, found by Ismail and Rahman in [22],
are slightly modified so as to make it transparent that these functions satisfy
a beautiful symmetry property. It essentially means that the geometric and the
spectral parameters are interchangeable in these functions. We call the
resulting functions the Askey-Wilson functions. Then, we show that by adding
bound states (with arbitrary weights) at specific points outside of the
continuous spectrum of some instances of the Askey-Wilson difference operator,
we can generate functions that satisfy a doubly infinite three-term recursion
relation and are also eigenfunctions of -difference operators of arbitrary
orders. Our result provides a discrete analogue of the solutions of the purely
differential version of the bispectral problem that were discovered in the
pioneering work [8] of Duistermaat and Gr\"unbaum.Comment: 42 pages, Section 3 moved to the end, minor correction
Economics of integrated crop management systems in the Dark Brown Soil Zone
Non-Peer ReviewedLow commodity prices, rising input costs, and increasing concerns about environmental degradation are encouraging producers in western Canada to consider alternative soil tillage and weed management methods that conserve resource inputs. However, little is known about the economic merits of these management changes. This study determines the effects of six integrated soil, cultural, and weed management practices on production costs, economic returns, and riskiness for a Wheat (W)-Canola (C)-Barley (B)-Pea (P) rotation in the Dark Brown Soil Zone of Saskatchewan
Irrotational binary neutron stars in quasiequilibrium
We report on numerical results from an independent formalism to describe the
quasi-equilibrium structure of nonsynchronous binary neutron stars in general
relativity. This is an important independent test of controversial numerical
hydrodynamic simulations which suggested that nonsynchronous neutron stars in a
close binary can experience compression prior to the last stable circular
orbit. We show that, for compact enough stars the interior density increases
slightly as irrotational binary neutron stars approach their last orbits. The
magnitude of the effect, however, is much smaller than that reported in
previous hydrodynamic simulations.Comment: 4 pages, 2 figures, revtex, accepted for publication in Phys. Rev.
Bispectral KP Solutions and Linearization of Calogero-Moser Particle Systems
A new construction using finite dimensional dual grassmannians is developed
to study rational and soliton solutions of the KP hierarchy. In the rational
case, properties of the tau function which are equivalent to bispectrality of
the associated wave function are identified. In particular, it is shown that
there exists a bound on the degree of all time variables in tau if and only if
the wave function is rank one and bispectral. The action of the bispectral
involution, beta, in the generic rational case is determined explicitly in
terms of dual grassmannian parameters. Using the correspondence between
rational solutions and particle systems, it is demonstrated that beta is a
linearizing map of the Calogero-Moser particle system and is essentially the
map sigma introduced by Airault, McKean and Moser in 1977.Comment: LaTeX, 24 page
Extensions of the matrix Gelfand-Dickey hierarchy from generalized Drinfeld-Sokolov reduction
The matrix version of the -KdV hierarchy has been recently
treated as the reduced system arising in a Drinfeld-Sokolov type Hamiltonian
symmetry reduction applied to a Poisson submanifold in the dual of the Lie
algebra . Here a
series of extensions of this matrix Gelfand-Dickey system is derived by means
of a generalized Drinfeld-Sokolov reduction defined for the Lie algebra
using the natural
embedding for any positive integer. The
hierarchies obtained admit a description in terms of a matrix
pseudo-differential operator comprising an -KdV type positive part and a
non-trivial negative part. This system has been investigated previously in the
case as a constrained KP system. In this paper the previous results are
considerably extended and a systematic study is presented on the basis of the
Drinfeld-Sokolov approach that has the advantage that it leads to local Poisson
brackets and makes clear the conformal (-algebra) structures related to
the KdV type hierarchies. Discrete reductions and modified versions of the
extended -KdV hierarchies are also discussed.Comment: 60 pages, plain TE
Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data
We present a map of the near subsurface hydrogen distribution on Mars, based on epithermal neutron data from the Mars Odyssey Neutron Spectrometer. The mapâs spatial resolution is approximately improved two-fold via a new form of the pixon image reconstruction technique. We discover hydrogen-rich mineralogy far from the poles, including âŻâŒ10âŻwt.% water equivalent hydrogen (WEH) on the flanks of the Tharsis Montes and âŻ>40âŻwt.% WEH at the Medusae Fossae Formation (MFF). The high WEH abundance at the MFF implies the presence of bulk water ice. This supports the hypothesis of recent periods of high orbital obliquity during which water ice was stable on the surface. We find the young undivided channel system material in southern Elysium Planitia to be distinct from its surroundings and exceptionally dry; there is no evidence of hydration at the location in Elysium Planitia suggested to contain a buried water ice sea. Finally, we find that the sites of recurring slope lineae (RSL) do not correlate with subsurface hydration. This implies that RSL are not fed by large, near-subsurface aquifers, but are instead the result of either small (âŻ<âŻ120 km diameter) aquifers, deliquescence of perchlorate and chlorate salts or dry, granular flows
Study of Effect on Teeth of Intermittent Fluoridation of a Community Water Supply
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67913/2/10.1177_00220345530320011601.pd
Implications of H.E.S.S. observations of pulsar wind nebulae
In this review paper on pulsar wind nebulae (PWN) we discuss the properties
of such nebulae within the context of containment against cross-field diffusion
(versus normal advection), the effect of reverse shocks on the evolution of
offset ``Vela-like'' PWN, constraints on maximum particle energetics, magnetic
field strength estimates based on spectral and spatial properties, and the
implication of such field estimates on the composition of the wind. A
significant part of the discussion is based on the High Energy Stereoscopic
System ({\it H.E.S.S.} or {\it HESS}) detection of the two evolved pulsar wind
nebulae Vela X (cocoon) and HESS J1825-137. In the case of Vela X (cocoon) we
also review evidence of a hadronic versus a leptonic interpretation, showing
that a leptonic interpretation is favored for the {\it HESS} signal. The
constraints discussed in this review paper sets a general framework for the
interpretation of a number of offset, filled-center nebulae seen by {\it HESS}.
These sources are found along the galactic plane with galactic latitudes
, where significant amounts of molecular gas is found. In these
regions, we find that the interstellar medium is inhomogeneous, which has an
effect on the morphology of supernova shock expansion. One consequence of this
effect is the formation of offset pulsar wind nebulae as observed.Comment: to appear in Springer Lecture Notes on Neutron Stars and Pulsars: 40
years after their discovery, eds. W. Becke
Anyonic order parameters for discrete gauge theories on the lattice
We present a new family of gauge invariant non-local order parameters for
(non-abelian) discrete gauge theories on a Euclidean lattice, which are in
one-to-one correspondence with the excitation spectrum that follows from the
representation theory of the quantum double D(H) of the finite group H.
These combine magnetic flux-sector labeled by a conjugacy class with an
electric representation of the centralizer subgroup that commutes with the
flux. In particular cases like the trivial class for magnetic flux, or the
trivial irrep for electric charge, these order parameters reduce to the
familiar Wilson and the 't Hooft operators respectively. It is pointed out that
these novel operators are crucial for probing the phase structure of a class of
discrete lattice models we define, using Monte Carlo simulations.Comment: 14 pages, 1 figur
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