1,986 research outputs found
Radiative corrections to the lattice gluon action for highly improved staggered quarks (HISQ) and the effect of such corrections on the static potential
We perform a perturbative calculation of the influence of dynamical HISQ
fermions on the perturbative improvement of the gluonic action in the same way
as we have previously done for asqtad fermions. We find the fermionic
contributions to the radiative corrections in the Luescher-Weisz gauge action
to be somewhat larger for HISQ fermions than for asqtad. Using one-loop
perturbation theory as a test, we estimate that omission of the fermion-induced
radiative corrections in dynamical asqtad simulations will give a measurable
effect. The one-loop result gives a systematic shift of about -0.6% in (r_1/a)
on the coarsest asqtad improved staggered ensembles. This is the correct sign
and magnitude to explain the scaling violations seen in Phi_B on dynamical
lattice ensembles.Comment: 10 pages, 5 figures. Minor corrections suggested by refere
Gauged O(n) spin models in one dimension
We consider a gauged O(n) spin model, n >= 2, in one dimension which contains
both the pure O(n) and RP(n-1) models and which interpolates between them. We
show that this model is equivalent to the non-interacting sum of the O(n) and
Ising models. We derive the mass spectrum that scales in the continuum limit,
and demonstrate that there are two universality classes, one of which contains
the O(n) and RP(n-1) models and the other which has a tuneable parameter but
which is degenerate in the sense that it arises from the direct sum of the O(n)
and Ising models.Comment: 9 pages, no figures, LaTeX sourc
S_3 and the L=1 Baryons in the Quark Model and the Chiral Quark Model
The S_3 symmetry corresponding to permuting the positions of the quarks
within a baryon allows us to study the 70-plet of L=1 baryons without an
explicit choice for the spatial part of the quark wave functions: given a set
of operators with definite transformation properties under the spin-flavor
group SU(3) x SU(2) and under this S_3, the masses of the baryons can be
expressed in terms of a small number of unknown parameters which are fit to the
observed L=1 baryon mass spectrum. This approach is applied to study both the
quark model and chiral constituent quark model. The latter theory leads to a
set of mass perturbations which more satisfactorily fits the observed L=1
baryon mass spectrum (though we can say nothing, within our approach, about the
physical reasonableness of the parameters in the fit). Predictions for the
mixing angles and the unobserved baryon masses are given for both models as
well as a discussion of specific baryons.Comment: 24 pages, requires picte
The contribution of O(alpha) radiative corrections to the renormalised anisotropy and application to general tadpole improvement schemes: addendum to "One loop calculation of the renormalised anisotropy for improved anisotropic gluon actions on a lattice" [hep-lat/0208010]
General O(alpha) radiative corrections to lattice actions may be interpreted
as counterterms that give additive contributions to the one-loop
renormalisation of the anisotropy. The effect of changing the radiative
coefficients is thus easily calculable. In particular, the results obtained in
a previous paper for Landau mean link improved actions apply in any tadpole
improvement scheme. We explain how this method can be exploited when tuning
radiatively improved actions. Efficient methods for self-consistently tuning
tadpole improvement factors are also discussed.Comment: 3 pages of revte
Overscreening in 1D lattice Coulomb gas model of ionic liquids
Overscreening in the charge distribution of ionic liquids at electrified
interfaces is shown to proceed from purely electrostatic and steric
interactions in an exactly soluble one dimensional lattice Coulomb gas model.
Being not a mean-field effect, our results suggest that even in higher
dimensional systems the overscreening could be accounted for by a more accurate
treatment of the basic lattice Coulomb gas model, that goes beyond the mean
field level of approximation, without any additional interactions.Comment: 4 pages 5 .eps figure
Movement patterns of cheetahs ( Acinonyx jubatus ) in farmlands in Botswana
Botswana has the second highest population of cheetah (Acinonyx jubatus) with most living outside protected areas. As a result, many cheetahs are found in farming areas which occasionally results in human-wildlife conflict. This study aimed to look at movement patterns of cheetahs in farming environments to determine whether cheetahs have adapted their movements in these human-dominated landscapes. We fitted high-time resolution GPS collars to cheetahs in the Ghanzi farmlands of Botswana. GPS locations were used to calculate home range sizes as well as number and duration of visits to landscape features using a time-based local convex hull method. Cheetahs had medium-sized home ranges compared to previously studied cheetah in similar farming environments. Results showed that cheetahs actively visited scent marking trees and avoided visiting homesteads. A slight preference for visiting game farms over cattle farms was found, but there was no difference in duration of visits between farm types. We conclude that cheetahs selected for areas that are important for their dietary and social needs and prefer to avoid human-occupied areas. Improved knowledge of how cheetahs use farmlands can allow farmers to make informed decisions when developing management practices and can be an important tool for reducing human-wildlife conflict
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