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1.
Recep Korkmaz 《Semigroup Forum》2009,78(3):528-535
In this paper we study dense inverse subsemigroups of topological inverse semigroups. We construct a topological inverse semigroup
from a semilattice. Finally, we give two examples of the closure of B
( −∞, ∞ )1, a topological inverse semigroup obtained by starting with the real numbers as a semilattice with the operation a
∨
b=sup{a,b}.
The author would like to thank to the referee for useful suggestions. 相似文献
2.
3.
In this article, the approximate amenability of semigroup algebra ?1(S) is investigated, where (S) is a uniformly locally finite inverse semigroup. Indeed, we show that for a uniformly locally finite inverse semigroup (S), the notions of amenability, approximate amenability and bounded approximate amenability of ?1(S) are equivalent. We use this to give a direct proof of the approximate amenability of ?1(S) for a Brandt semigroup (S). Moreover, we characterize the approximate amenability of ?1(S), where S is a uniformly locally finite band semigroup. 相似文献
4.
Let R be an associative ring with unit, let S be a semigroup with zero, and let RS be a contracted semigroup ring. It is proved that if RS is radical in the sense of Jacobson and if the element 1 has infinite additive order, then S is a locally finite nilsemigroup. Further, for any semigroup S, there is a semigroup T S such that the ring RT is radical in the Brown--McCoy sense. Let S be the semigroup of subwords of the sequence abbabaabbaababbab..., and let F be the two-element field. Then the ring FS is radical in the Brown--McCoy sense and semisimple in the Jacobson sense. 相似文献
5.
If S is a semigroup, the global (or the power semigroup) of S is the set P(S) of all nonempty subsets of S equipped with a naturally defined multiplication. A class K of semigroups is globally determined if any two semigroups of K with isomorphic globals are themselves isomorphic. We study properties of globals of idempotent semigroups and show, in particular, that the class of normal bands is globally determined. 相似文献
6.
在空间Lp(Rn),1≤p<∞中,Poison算子半群e--△z是右半平面Rez>0上的解析半群.本文考虑它的边界值,证明了闭稠定算子-i-△对某个α≥0生成了一个指数有界(I+-△)-α 半群. 相似文献
7.
《代数通讯》2013,41(7):2609-2615
Abstract Regular semigroups S with the property eS ? Se or Se ? eS for all idempotents e ∈ S include all left and right Clifford semigroups. Characterizations of such semigroups are given and their structure investigated, in particular in terms of spined products of left and right Clifford semigroups with respect to Clifford semigroups. 相似文献
8.
ABSTRACT The investigation of regular F-abundant semigroups is initiated. In fact, F-abundant semigroups are generalizations of regular cryptogroups in the class of abundant semigroups. After obtaining some properties of such semigroups, the construction theorem of the class of regular F-abundant semigroups is obtained. In addition, we also prove that a regular F-abundant semigroup is embeddable into a semidirect product of a regular band by a cancellative monoid. Our result is an analogue of that of Gomes and Gould on weakly ample semigroups, and also extends an earlier result of O'Carroll on F-inverse semigroups. 相似文献
9.
The main result of the paper is a structure theorem concerning the ideal extensions of archimedean ordered semigroups. We
prove that an archimedean ordered semigroup which contains an idempotent is an ideal extension of a simple ordered semigroup
containing an idempotent by a nil ordered semigroup. Conversely, if an ordered semigroup S is an ideal extension of a simple ordered semigroup by a nil ordered semigroup, then S is archimedean. As a consequence, an ordered semigroup is archimedean and contains an idempotent if and only if it is an
ideal extension of a simple ordered semigroup containing an idempotent by a nil ordered semigroup. 相似文献
10.
Torben Maack Bisgaard 《Journal of Theoretical Probability》1996,9(3):631-645
If (
j
) is a sequence of measures onR
k
having momentss
n
(
j
) of all ordersnN
0
k
and if for eachnN
0
k
the sequence (s
n
j
))
jN
converges to somet
n
R then some subsequence of (
j
) converges weakly to a measure with moments of all orders satisfyings
n
()=t
n
for allnN0/k
. Thisindeterminate method of moments and the continuity theorems in probability theory suggest a common generalization, dealing with a commutative semigroupS, with involution and a neutral element, and measures on the dual semigroupS
* ofcharacters on S—hermitian multiplicative complex functions not identically zero. In this setting, a continuity theorem holds for measures on the set of bounded characters,(2) and an indeterminate method of moments whenS is finitely generated.(2) The latter result is generalized in the present paper to the case of arbitraryS. This leads to a generalization of Haviland's criterion for theK-moment problem, and to a continuity theorem for the so-called perfect semigroups. 相似文献
11.
We study algebraic and topological properties of topological semigroups containing a copy of the bicyclic semigroup C(p,q). We prove that a topological semigroup S with pseudocompact square contains no dense copy of C(p,q). On the other hand, we construct a (consistent) example of a pseudocompact (countably compact) Tychonoff semigroup containing a copy of C(p,q). 相似文献
12.
Automatic Completely-Simple Semigroups 总被引:2,自引:0,他引:2
C. M. Campbell E. F. Robertson M. Ruškuc R. M. Thomas 《Acta Mathematica Hungarica》2002,95(3):201-215
The notion of automaticity has been widely studied in groups and some progress has been made in understanding the notion in the wider context of semigroups. The purpose of this paper is to study automatic completely-simple semigroups. We show that, if
is a completely-simple semigroup
(with
and
finite), then
is automatic if and only if the group
is automatic. As a consequence, we deduce that automatic completely-simple semigroups are finitely presented. We also show that automatic completely-simple semigroups are characterized by the fellow traveller property and also that the existence of an automatic structure is independent of the choice of generating set. 相似文献
13.
14.
Tim Stokes 《代数通讯》2013,41(9):3979-4007
A D-semigroup S is a semigroup equipped with an operation D satisfying laws asserting that for a ∈ S, D(a) is the smallest e in some set of idempotents U ? S for which ea = a. D-semigroups correspond to left-reduced U-semiabundant semigroups. The basic properties and many examples of D-semigroups are given. Also considered are D-rings, whose multiplicative semigroup is a D-semigroup. Rickart *-rings provide important examples, and the most general D-rings for which the elements of the form D(a) constitute a lattice under the same meet and join operations as for Rickart *-rings are described. 相似文献
15.
16.
We consider semigroup S of a rank 1 valuation ? centered on a local ring R. We show that the Hilbert polynomial of R gives a bound on the growth of the valuation semigroup S. This allows us to give a very simple example of a well ordered subsemigroup of Q+, which is not a value semigroup of a local domain. We also consider the rates of growth which are possible for S. We show that quite exotic behavior can occur. In the final section, we consider the general question of characterizing rank 1 value semigroups. 相似文献
17.
A. N. Krasil'nikov 《Mathematical Notes》1997,62(4):426-433
To each associative ringR we can assign the adjoint Lie ringR
(−) (with the operation(a,b)=ab−ba) and two semigroups, the multiplicative semigroupM(R) and the associated semigroupA(R) (with the operationaob=ab+a+b). It is clear that a Lie ringR
(−) is commutative if and only if the semigroupM(R) (orA(R)) is commutative. In the present paper we try to generalize this observation to the case in whichR
(−) is a nilpotent Lie ring. It is proved that ifR is an associative algebra with identity element over an infinite fieldF, then the algebraR
(−) is nilpotent of lengthc if and only if the semigroupM(R) (orA(R)) is nilpotent of lengthc (in the sense of A. I. Mal'tsev or B. Neumann and T. Taylor). For the case in whichR is an algebra without identity element overF, this assertion remains valid forA(R), but fails forM(R). Another similar results are obtained.
Translated fromMatematicheskie Zametki, Vol. 62, No. 4, pp. 510–519, October, 1997.
Translated by A. I. Shtern 相似文献
18.
Let
be a dense sub-semigroup of ℝ+, and let X be a separable, reflexive Banach space. This note contains a proof that every weakly continuous contractive semigroup of
operators on X over
can be extended to a weakly continuous semigroup over ℝ+. We obtain similar results for nonlinear, nonexpansive semigroups as well. As a corollary we characterize all densely parametrized
semigroups which are extendable to semigroups over ℝ+.
O.M. Shalit was partially supported by the Gutwirth Fellowship. 相似文献
19.
J. C. Rosales P. A. Garcí a-Sá nchez 《Proceedings of the American Mathematical Society》2008,136(2):475-477
Let be a numerical semigroup. Then there exists a symmetric numerical semigroup such that .
20.
Existence and nonexistence of hypercyclic semigroups 总被引:1,自引:0,他引:1
L. Bernal-Gonzá lez K.-G. Grosse-Erdmann 《Proceedings of the American Mathematical Society》2007,135(3):755-766
In these notes we provide a new proof of the existence of a hypercyclic uniformly continuous semigroup of operators on any separable infinite-dimensional Banach space that is very different from--and considerably shorter than--the one recently given by Bermúdez, Bonilla and Martinón. We also show the existence of a strongly dense family of topologically mixing operators on every separable infinite-dimensional Fréchet space. This complements recent results due to Bès and Chan. Moreover, we discuss the Hypercyclicity Criterion for semigroups and we give an example of a separable infinite-dimensional locally convex space which supports no supercyclic strongly continuous semigroup of operators.