423 research outputs found
The categorical theory of relations and quantizations
In this paper we develope a categorical theory of relations and use this
formulation to define the notion of quantization for relations. Categories of
relations are defined in the context of symmetric monoidal categories. They are
shown to be symmetric monoidal categories in their own right and are found to
be isomorphic to certain categories of bicomodules. Properties of
relations are defined in terms of the symmetric monoidal structure. Equivalence
relations are shown to be commutative monoids in the category of relations.
Quantization in our view is a property of functors between monoidal categories.
This notion of quantization induce a deformation of all algebraic structures in
the category, in particular the ones defining properties of relations like
transitivity and symmetry.Comment: corrected typo
Theory of linear G-difference equations
We introduce the notion of difference equation defined on a structured set.
The symmetry group of the structure determines the set of difference operators.
All main notions in the theory of difference equations are introduced as
invariants of the symmetry group. Linear equations are modules over the skew
group algebra, solutions are morphisms relating a given equation to other
equations,symmetries of an equation are module endomorphisms and conserved
structures are invariants in the tensor algebra of the given equation. We show
that the equations and their solutions can be described through representations
of the isotropy group of the symmetry group of the underluing set. We relate
our notion of difference equations and solutions to systems of classical
difference equations and their solutions and show that our notions include
these as a special case.Comment: 34 page
Constructing a partially transparent computational boundary for UPPE using leaky modes
In this paper we introduce a method for creating a transparent computational
boundary for the simulation of unidirectional propagation of optical beams and
pulses using leaky modes. The key element of the method is the introduction of
an artificial-index material outside a chosen computational domain and
utilization of the quasi-normal modes associated with such artificial
structure. The method is tested on the free space propagation of TE
electromagnetic waves. By choosing the material to have appropriate optical
properties one can greatly reduce the reflection at the computational boundary.
In contrast to the well-known approach based on a perfectly matched layer, our
method is especially well suited for spectral propagators.Comment: 32 pages, 19 figure
Copepod reaction to odor stimuli influenced by cestode infection
The cestode Schistocephalus solidus uses copepods as first and sticklebacks as second intermediate hosts. For transmission, an infected copepod has to be preyed upon by a stickleback. We used copepods of the species Macrocy albidus to test whether infected and uninfected copepods differ in their reaction to two kind of simultaneously presented odors: odors of sticklebacks and odors of sticklebacks and conspecificz. By giving this choice, we attempted to force the copepods to make a trade-off between the benefit of risk dilution and possible predator confusion and the costs of food competition and other disadvantages induced by conspecifics. Within 1-8 h after last feeding, uninfected copepods clearly preferred the odors of conspeciflcs under the chemically simulated threat of predation. This was in contrast to the infected copepods, who tended to avoid the odor of conspecifics. When the time between experiment and last feeding varied, infected copepods showed an increas preference for fish water only (or avoided conspecthcs) with increasing hunger level This suggests that S. solidus benefits from hunger-induced behavioral changes of its copepod host by influencing its microhabitat selection. The same effect could be found in both sexes; however, it was significantly more pronounced in male than in female copepods. We propose several hypotheses that could explain the difference between the sexes in their infection-dependent microhabitat selectio
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