2,669 research outputs found
Endomorphisms of the lattice of epigroup varieties
We examine varieties of epigroups as unary semigroups, that is semigroups
equipped with an additional unary operation of pseudoinversion. The article
contains two main results. The first of them indicates a countably infinite
family of injective endomorphisms of the lattice of all epigroup varieties. An
epigroup variety is said to be a variety of finite degree if all its
nilsemigroups are nilpotent. The second result of the article provides a
characterization of epigroup varieties of finite degree in a language of
identities and in terms of minimal forbidden subvarieties. Note that the first
result is essentially used in the proof of the second one.Comment: In comparison with the previous version, we eliminate a few typos
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The lattice of varieties of implication semigroups
In 2012, the second author introduced and examined a new type of algebras as
a generalization of De Morgan algebras. These algebras are of type (2,0) with
one binary and one nullary operation satisfying two certain specific
identities. Such algebras are called implication zroupoids. They invesigated in
a number of articles by the second author and J.M.Cornejo. In these articles
several varieties of implication zroupoids satisfying the associative law
appeared. Implication zroupoids satisfying the associative law are called
implication semigroups. Here we completely describe the lattice of all
varieties of implication semigroups. It turns out that this lattice is
non-modular and consists of 16 elements.Comment: Compared with the previous version, we rewrite Section 3 and add
Appendixes A and
Crossover between distinct mechanisms of microwave photoresistance in bilayer systems
We report on temperature-dependent magnetoresistance measurements in balanced
double quantum wells exposed to microwave irradiation for various frequencies.
We have found that the resistance oscillations are described by the
microwave-induced modification of electron distribution function limited by
inelastic scattering (inelastic mechanism), up to a temperature of T*~4 K. With
increasing temperature, a strong deviation of the oscillation amplitudes from
the behavior predicted by this mechanism is observed, presumably indicating a
crossover to another mechanism of microwave photoresistance, with similar
frequency dependence. Our analysis shows that this deviation cannot be fully
understood in terms of contribution from the mechanisms discussed in theory.Comment: 7 pages, 4 figure
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