Canonizing partition theorems: Diversification, products, and iterated versions

We present an abstract framework for canonizing partition theorems. The concept of attribute functions and of diversification allows us to establish a canonizing product theorem, generalizing previous results of [19.], 71–83] for the situation of Ramsey's theorem. As applications we mention a canonizing product theorem for arithmetic progressions and for finite geometric arguesian lattices. We show that finite sets and finite vector spaces have the diversification property. Along these lines, iterated versions of the [6.], 249–255] and its q-analogue for finite vector spaces [[24.], 219–239] are derived.     

Solution of a problem of Ulam

In this paper we solve the following Ulam problem: “Give conditions in order for a linear mapping near an approximately linear mapping to exist” and establish results involving a product of powers of norms [[5.]; [5.]; [5.]]. There has been much activity on a similar “ -isometry” problem of Ulam [ [1.], 633–636; [2.], 263–277; [4.]]. This work represents an improvement and generalization of the work of [3.], 222–224].     

Structure of monogenic inverse semigroups

Some properties of monogenic inverse semigroups are considered. In particular, in a free monogenic inverse semigroup we study the disposition of idempotents, describe the structure of ideals, classify the congruences.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 103, pp. 66–75, 1980.     

Idempotent probabilities on semigroups

Summary In this paper, idempotent probability measures have been considered on semigroups which are locally compact or metric and satisfy: (*) A ^–1 B and Ax ^–1 are compact whenever A and B are so, for every x in the semigroup. Such semigroups are more general than compact semigroups which do admit of such measures. On such semigroups we can construct such measures by the usual process if there is a compact sub-semigroup. It is shown in this paper that if such a measure exists in such semigroups, then it must be such an extension measure. Some related results concerning the conditions (*) are also discussed here.     

On left C-wrpp semigroups

It is known that a C–rpp semigroup can be described as a strong semilattice of left cancellative monoids. In this paper, we introduce the class of left C–wrpp semigroups which includes the class of left C–rpp semigroups as a subclass. We shall particularly show that the semi-spined product of a left regular band and a C–wrpp semigroup forms a curler which is a left C–wrpp semigroup and vice versa. Results obtained by Fountain and Tang on C–rpp semigroups are extended and strengthened.     

A Fredholm-type theory for third-kind linear integral equations

The third-kind linear integral equation where g(t) vanishes at a finite number of points in (a, b), is considered. In general, the Fredholm Alternative theory [[5.]] does not hold good for this type of integral equation. However, imposing certain conditions on g(t) and K(t, t′), the above integral equation was shown [[1.], 49–57] to obey a Fredholm-type theory, except for a certain class of kernels for which the question was left open. In this note a theory is presented for the equation under consideration with some additional assumptions on such kernels.     

Inverse subsemigroups and classes of finite aperiodic semigroups

We prove a number of results related to finite semigroups and their inverse subsemigroups, including the following. (1) A finite semigroup is aperiodic if and only if it is a homomorphic image of a finite semigroup whose inverse subsemigroups are semilattices. (2) A finite inverse semigroup can be represented by order-preserving mappings on a chain if and only if it is a semilattice. Finally, we introduce the concept of pseudo-small quasivariety of finite semigroups, generalizing the concept of small variety.     

Domain theory and mirror properties in inverse semigroups

Inverse semigroups are a class of semigroups whose structure induces a compatible partial order. This partial order is examined so as to establish mirror properties between an inverse semigroup and the semilattice of its idempotent elements, such as continuity in the sense of domain theory.     

Möbius functions and semigroup representation theory

This paper explores several applications of Möbius functions to the representation theory of finite semigroups. We extend Solomon's approach to the semigroup algebra of a finite semilattice via Möbius functions to arbitrary finite inverse semigroups. This allows us to explicitly calculate the orthogonal central idempotents decomposing an inverse semigroup algebra into a direct product of matrix algebras over group rings. We also extend work of Bidigare, Hanlon, Rockmore and Brown on calculating eigenvalues of random walks associated to certain classes of finite semigroups; again Möbius functions play an important role.     

Definability of vector groups by endomorphism semigroups

Some conditions for torsion-free Abelian groups to be isomorphic are found; the groups in question are decomposable into a direct product of rank 1 groups with isomorphic endomorphism semigroups.Translated fromAlgebra i Logika, Vol. 33, No. 4, pp. 422–428, July-August, 1994.     

Running tails as codimension two quasi-solitons in excitation taxis waves with negative refractoriness

Using a Lindblad dissipation dynamics [Lindblad G. On the generators of quantum dynamical semigroups. Commun Math Phys 1976;48:119–130 and see also Gorini V, Frigerio A, Verri M, Kossakowski A, Sudarshan ECG. Properties of quantum Markovian master equations. Rep Math Phys 1978;13:149–173; Alicki R, Messer J. Nonlinear quantum dynamical semigroups for many-body open systems. J Stat Phys 1983;32:299–312.] for biological rate equations we derive a one-component discrete dynamics for the spread of Avian Influenza. Numerical solutions of the difference equations are calculated and compared with measurement data.     

Density Theorems for Graded Rings

The main purpose of this paper is to prove three density theorems for rings graded by semigroups and modules graded by acts over these semigroups with some cancellation conditions. In addition, the density theorem for superrings and supermodules is proved.__________Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 9, No. 1, pp. 27–49, 2003.     

Quasi-ideal transversals of abundant semigroups and spined products

We provide a new and much simpler structure for quasi-ideal adequate transversals of abundant semigroups in terms of spined products, which is similar in nature to that given by Saito in Proc. 8th Symposium on Semigroups, pp. 22–25 (1985) for weakly multiplicative inverse transversals of regular semigroups. As a consequence we deduce a similar result for multiplicative transversals of abundant semigroups and also consider the case when the semigroups are in fact regular and provide some new structure theorems for inverse transversals.     

Probabilistic Number Theory in Additive Arithmetic Semigroups, III

We extend the investigation of quantitative mean-value theorems of completely multiplicative functions on additive arithmetic semigroups given in our previous paper. Then the new and old quantitative mean-value theorems are applied to the investigation of local distribution of values of a special additive function *(a). The result is unexpected from the point of view of classical number theory. This reveals the fact that the essential divergence of the theory of additive arithmetic semigroups from classical number theory is not related to the existence of a zero of the zeta function Z(y) at y = –q ^–1.     

Inverse semigroups determined by their lattices of convex inverse subsemigroups I

Every inverse semigroup possesses a natural partial order and therefore convexity with respect to this order is of interest. We study the extent to which an inverse semigroup is determined by its lattice of convex inverse subsemigroups; that is, if the lattices of two inverse semigroups are isomorphic, how are the semigroups related? We solve this problem completely for semilattices and for inverse semigroups in general reduce it to the case where the lattice isomorphism induces an isomorphism between the semilattices of idempotents of the semigroups. For many inverse semigroups, such as the monogenic ones, this case is the only one that can occur. In Part II, a study of the reduced case enables us to prove that many inverse semigroups, such as the free ones, are strictly determined by their lattices of convex inverse subsemigroups, and to show that the answer obtained here for semilattices can be extended to a broad class of inverse semigroups, including all finite, aperiodic ones. Received September 24, 2002; accepted in final form December 15, 2002.     

On the Convergence of Hyperbolic Semigroups in Variable Hilbert Spaces

Resolvent convergence is considered for nonnegative self-adjoint operators acting in a variable Hilbert space H, with the limit of the resolvents being a pseudoresolvent. This convergence is used for passing to the limit in the corresponding hyperbolic operator equations in H viewed from the standpoint of semigroups. The scheme studied here can be applied to homogenization of nonstationary problems of elasticity for thin structures.__________Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 24, pp. 215–249, 2004.     

The structure of ?*-inverse semigroups

The concepts of ℒ*-inverse semigroups and left wreath products of semigroups are introduced. It is shown that the ℒ*-inverse semigroup can be described as the left wreath product of a type A semigroup Γ and a left regular band B together with a mapping which maps the semigroup Γ into the endomorphism semigroup End(B). This result generalizes the structure theorem of Yamada for the left inverse semigroups in the class of regular semigroups. We shall also provide a constructed example for the ℒ*-inverse semigroups by using the left wreath products.