3,388 research outputs found
SO(3) vortices and disorder in the 2d SU(2) chiral model
We study the correlation function of the 2d SU(2) principal chiral model on
the lattice. By rewriting the model in terms of Z(2) degrees of freedom coupled
to SO(3) vortices we show that the vortices play a crucial role in disordering
the correlations at low temperature. Using a series of exact transformations we
prove that, if satisfied, certain inequalities between vortex correlations
imply exponential fall-off of the correlation function at arbitrarily low
temperatures. We also present some Monte Carlo evidence that these correlation
inequalities are indeed satisfied. Our method can be easily translated to the
language of 4d SU(2) gauge theory to establish the role of corresponding SO(3)
monopoles in maintaining confinement at small couplings.Comment: 13 pages LaTe
Absence of confinement in the absence of vortices
We consider the Wilson loop expectation in SU(2) lattice gauge theory in the
presence of constraints. The constraints eliminate from the functional measure
gauge field configurations whose physical interpretation is that of thick
center vortices linking with the loop. We give a simple proof that, for
dimension , the so constrained Wilson loop follows perimeter law,
i.e. non-confining behavior, at weak coupling (low temperature). Thus the
presence of vortex configurations is a necessary condition for confinement.Comment: 14 pages, LaTeX fil
The effect of companion planting on the abundance of pest complex and its parasitism rate on white cabbage
The findings of this paper could help to develop and maintain a sustainable cabbage production by the enhancement of natural pest control with the help of companion planting. Our results indicate that Lobularia maritima (Brassicaceae) could be used to attract pests of cruciferous plants away from the crop.
Centaurea cyanus (Asteraceae) and Fagopyrum esculentum (Polygonaceae) could be used to suppress pests of cruciferous crops and to increase parasitism rate by fostering parasitoids
Aligator.jl - A Julia Package for Loop Invariant Generation
We describe the Aligator.jl software package for automatically generating all
polynomial invariants of the rich class of extended P-solvable loops with
nested conditionals. Aligator.jl is written in the programming language Julia
and is open-source. Aligator.jl transforms program loops into a system of
algebraic recurrences and implements techniques from symbolic computation to
solve recurrences, derive closed form solutions of loop variables and infer the
ideal of polynomial invariants by variable elimination based on Gr\"obner basis
computation
Fourier decomposition and frequency analysis of the pulsating stars with P<1 d in the OGLE database. I. Monoperiodic Delta Scuti, RRc and RRab variables. Separation criteria and particularities
The OGLE database is revisited to investigate in more detail the properties
of the Fourier parameters. Methodological improvements led us to identify a
clear separation among High-Amplitude Delta Scuti (HADS), RRc and RRab stars.
The bimodal distribution of the R21 parameter in HADS stars is explained as a
contamination effect from RRc stars: there is evidence that all stars with
0.20<P<0.25 d are RRc variables. The previously claimed existence of a subclass
of unusual HADS is demonstrated to be a spurious result. Candidate overtone
pulsators are found among HADS and RRc variables. The properties of the Fourier
parameters are discussed as a function of the physical conditions in the stars
involved. Among the field RRab stars we detected different light-curve groups
producing distinct "tails" in the Fourier plots for P>0.55 d; evolutionary
phases or the combination of different physical conditions (not only
metallicity) are suggested to explain this separation, observed also in the
cluster RRab stars. The stellar parameters of RRc stars in a given globular
cluster show different tendencies than those of RRc stars from different
clusters.Comment: 12 pages (in A&A style), 14 eps figures. Accepted for A&A Main
Journal. Table 3, 4 and 5 are also included as ascii files. The atlas of the
light curves and least-squares fits can be requested from the autho
- …