Some relations on the lattice of varieties of completely regular semigroups

Mario Petrich

Displaying similar documents to “Some relations on the lattice of varieties of completely regular semigroups”

On sandwich sets and congruences on regular semigroups

Mario Petrich (2006)

Czechoslovak Mathematical Journal

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Let $S$ be a regular semigroup and $E (S)$ be the set of its idempotents. We call the sets $S (e, f) f$ and $e S (e, f)$ one-sided sandwich sets and characterize them abstractly where $e, f \in E (S)$ . For $a, a^{'} \in S$ such that $a = a a^{'} a$ , $a^{'} = a^{'} a a^{'}$ , we call $S (a) = S (a^{'} a, a a^{'})$ the sandwich set of $a$ . We characterize regular semigroups $S$ in which all $S (e, f)$ (or all $S (a))$ are right zero semigroups (respectively are trivial) in several ways including weak versions of compatibility of the natural order. For every $a \in S$ , we also define $E (a)$ as the set of all idempotets $e$ such that, for any congruence...

Adding or removing an element from a pseudo-symmetric numerical semigroup

J. C. Rosales (2006)

Bollettino dell'Unione Matematica Italiana

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If $S$ is a pseudo-symmetric numerical semigroup, $g$ is its Frobenius number and $S$ is a minimal generator of $S$ , then $S\cup\{g\}$ , $S\setminus\{g\}$ S and $S\cup\{\frac{1}{2}g,g\}$ are also numerical semigroups. In this paper we study these constructions.

Some Remarks on Prym-Tyurin Varieties

Giuliano Parigi (2007)

Bollettino dell'Unione Matematica Italiana

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The aims of the present paper can be described as follows: a) In [2] Beauville showed that if some endomorphism $u$ a Jacobian $J(C)$ has connected kernel, the principal polarization on $J(C)$ induces a multiple of the principal polarization on the image of $u$ . We reformulate and complete this theorem proving "constructively" the following: Theorem. Let $Z\subset J(C)$ be an abelian subvariety and $Y$ its complementary variety. $Z$ is a Prym-Tyurin variety with respect to $J(C)$ if and only if the following sequence...

Inverses of generators of nonanalytic semigroups

Ralph deLaubenfels (2009)

Studia Mathematica

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Suppose A is an injective linear operator on a Banach space that generates a uniformly bounded strongly continuous semigroup ${e^{t A}}_{t \geq 0}$ . It is shown that $A^{- 1}$ generates an $O (1 + τ) A {(1 - A)}^{- 1}$ -regularized semigroup. Several equivalences for $A^{- 1}$ generating a strongly continuous semigroup are given. These are used to generate sufficient conditions on the growth of ${e^{t A}}_{t \geq 0}$ , on subspaces, for $A^{- 1}$ generating a strongly continuous semigroup, and to show that the inverse of -d/dx on the closure of its image in L¹([0,∞)) does not generate...

Regular elements and Green's relations in Menger algebras of terms

Klaus Denecke, Prakit Jampachon (2006)

Discussiones Mathematicae - General Algebra and Applications

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Defining an (n+1)-ary superposition operation $S^{n}$ on the set $W_{τ} (X_{n})$ of all n-ary terms of type τ, one obtains an algebra $n - c l o n e τ : = (W_{τ} (X_{n}); S^{n}, x_{1}, . . ., x_{n})$ of type (n+1,0,...,0). The algebra n-clone τ is free in the variety of all Menger algebras ([9]). Using the operation $S^{n}$ there are different possibilities to define binary associative operations on the set $W_{τ} (X_{n})$ and on the cartesian power $W_{τ} {(X_{n})}^{n}$ . In this paper we study idempotent and regular elements as well as Green’s relations in semigroups of terms with these binary associative...

On the K-theory of the $C^{*}$ -algebra generated by the left regular representation of an Ore semigroup

Joachim Cuntz, Siegfried Echterhoff, Xin Li (2015)

Journal of the European Mathematical Society

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We compute the $K$ -theory of $C^{*}$ -algebras generated by the left regular representation of left Ore semigroups satisfying certain regularity conditions. Our result describes the $K$ -theory of these semigroup $C^{*}$ -algebras in terms of the $K$ -theory for the reduced group $C^{*}$ -algebras of certain groups which are typically easier to handle. Then we apply our result to specific semigroups from algebraic number theory.

Congruences between modular forms and related modules

Miriam Ciavarella (2006)

Bollettino dell'Unione Matematica Italiana

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We fix $\ell$ a prime and let $M$ be an integer such that $\ell\operatorname{\not|}M$ ; let $f\in S_{2}(\Gamma_{1}(M\ell^{2}))$ be a newform supercuspidal of fixed type at $\ell$ and special at a finite set of primes. For an indefinite quaternion algebra over $Q$ , of discriminant dividing the level of $f$ , there is a local quaternionic Hecke algebra $T$ associated to $f$ . The algebra $T$ acts on a module $M_{f}$ coming from the cohomology of a Shimura curve. Applying the Taylor-Wiles criterion and a recent Savitt's theorem, $T$ is the universal deformation ring of a global...

Some Separation Axioms Via Ideals

D. Sivaraj, V. Renuka Devi (2007)

Bollettino dell'Unione Matematica Italiana

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We introduce a new class of spaces, called Hausdorff modulo $\mathcal{I}$ or $T_{2}$ mod $\mathcal{I}$ spaces with respect to an ideal $\mathcal{I}$ which contains the class of all Hausdorff spaces. Characterizations of these spaces are given and their properties are investigated. The concept of compactness modulo an ideal $\mathcal{I}$ was introduced by Newcomb in 1967 and studied by Hamlett and Jankovic in 1990. We study the properties of $\mathcal{I}$ -compact subsets in Hausdorff modulo $\mathcal{I}$ spaces and generalize some results of Hamlett and Jankovic....

Partial Hölder continuity results for solutions of non linear non variational elliptic systems with limit controlled growth

Luisa Fattorusso, Giovanna Idone (2002)

Bollettino dell'Unione Matematica Italiana

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Let $Ω$ be a bounded open subset of $R^{n}$ , $n > 4$ , of class $C^{2}$ . Let $u \in H^{2} (Ω)$ a solution of elliptic non linear non variational system $a (x, u, D u, H (u)) = b (x, u, D u)$ where $a (x, u, μ, ξ)$ and $b (x, u, μ)$ are vectors in $R^{N}$ , $N \geq 1$ , measurable in $x$ , continuous in $(u, μ, ξ)$ and $(u, μ)$ respectively. Here, we demonstrate that if $b (x, u, μ)$ has limit controlled growth, if $a (x, u, μ, ξ)$ is of class $C^{1}$ in $ξ$ and satisfies the Campanato condition $(A)$ and, together with $\frac{\partial a}{\partial ξ}$ , certain continuity assumptions, then the vector $D u$ is partially Hölder continuous for every exponent $α < 1 - \frac{n}{p}$ .

On semigroups of $σ$ -endomorphisms

Iwanik, Anzelm

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$L^{p}$ Regularity of Transmission Problems in Dihedral Domains

Aissa Aibeche, Wided Chikouche, Serge Nicaise (2007)

Bollettino dell'Unione Matematica Italiana

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We consider the transmission problem for the Laplace operator in a straight cylinder with data in $L^{p}$ . Applying the theory of the sums of operators in Banach spaces, we prove that the solution admits a decomposition into a regular part in $W^{2,p}$ and an explicit singular part.