共查询到20条相似文献,搜索用时 31 毫秒
1.
Carlton J. Maxson 《Semigroup Forum》1972,5(1):160-166
In this paper we investigate semigroups of ring endomorphisms of several classes of rings. As one result we find that the
Green relations in the endomorphism semigroup, End R, for a ring R in a given class, are restrictions of those in the transformation
semigroup
. 相似文献
2.
Evgeni Ja. Gabovič 《Semigroup Forum》1972,4(1):335-340
A semigroup S is calledE-semigroup (
-semigroup) if every (finitely generated) subsemigroup of S is an endomorphic image of S and Ē-semigroup (
-semigroup) if every subsemigroup of S is an E-semigroup
-semigroup. All classes X ε {Ē,
, E,
} are distinct even in the case of semilattices. It is established when a free band (semilattice) is an X-semigroup.
-,
- and Ē-chains and E-chains with identity or zero, Ē-and
, X-bands with identity and X-semigroups with identity and zero are found. 相似文献
3.
William R. Nico 《Semigroup Forum》1972,5(1):145-153
Let S be a monoid such that every left S-operand satisfies the ascending chain condition on orbits. Let X be an indecomposable
[0-indecomposable] left S-operand. There is a descending chain of suboperands of X defined in terms of maximal orbits. If
this chain terminates after a finite number of terms, the last non-empty [non-zero] term defines a distinguished collection
(X) [
0(X)] of disjoint [0-disjoint] orbits in X. The assumption that
(X) [
0(X)] is finite for all appropriate X, together with the additional assumption that every left S-operand satisfies the d.c.c.
on orbits, implies that S has a unique minimal left ideal [that the principal left ideals outside of the minimal ideal are
linearly ordered].
This research supported in part by the National Science Foundation. 相似文献
4.
A. Batbedat 《Semigroup Forum》1985,31(1):69-86
- The concept of left F-regular semigroups was first defined by Batbedat at the Oberwolfach meeting in 1981. It generalizes the notion of F-regular semigroup introduced by Edwards [4], itself a generalization of the F-inverse semigroups defined by McFadden/O’Carroll [6]
- In the present paper we generalize the results of [4] and [6] by defining two preorders and ? on a monoid S with a distinguished band E, as follows: iff x=ay for some a∈E xδy iff x=yb for some b∈E
- When S is regular orthodox and E=E(S), is the preorder of [1] p. 29 and is the order of [1] p. 31 (the order of [4]): in fact is the natural partial order introduced by Nambooripad [7].
- In b), we define the relation Σ on S: xΣy iff exe=eye for some e∈E Then we consider the congruence σ generated by Σ.
- DEFINITION. S is left FE-monoid if each σ-class contain a greatest element with respect to .
- PARTICULAR CASES. When S is regular, S is left FE-regular. When S is regular orthodox and E=E(S), S is left F-regular.
- We describe the structure of left F-regular semigroups like in [1], [2], [4] and [6]. Note that every left F-regular semigroup is a gammasemigroup [3]
- Particular Cases (gamma morphism) and applications (congruences).
5.
Orthodox semigroups whose idempotents satisfy a certain identity 总被引:2,自引:0,他引:2
Miyuki Yamada 《Semigroup Forum》1973,6(1):113-128
An orthodox semigroup S is called a left [right] inverse semigroup if the set of idempotents of S satisfies the identity xyx=xy
[xyx=yx]. Bisimple left [right] inverse semigroups have been studied by Venkatesan [6]. In this paper, we clarify the structure
of general left [right] inverse semigroups. Further, we also investigate the structure of orthodox semigroups whose idempotents
satisfy the identity xyxzx=xyzx. In particular, it is shown that the set of idempotents of an orthodox semigroup S satisfies
xyxzx=xyzx if and only if S is isomorphic to a subdirect product of a left inverse semigroup and a right inverse semigroup. 相似文献
6.
G. R. Baird 《Semigroup Forum》1972,5(1):228-235
Let S be a regular semigroup. The lattice of all idempotent-separating congruences on S and the lattice of all group congruences on S are both modular sublattices of the full lattice of congruences on S. It is evident that the set theoretical union of these two sublattices, (S), is also a sublattice of the full lattice of congruences on S. It is natural to ask: Under what conditions is the sublattice (S) modular? In this paper we obtain a necessary and sufficient condition for the sublattice (S) to be modular when S is what we call a θ-regular semigroup. Bisimple ω-semigroups and simple regular ω-semigroups are θ-regular semigroups and so this paper extends the work of Munn [5] and Baird [1]. 相似文献
7.
Satoru Fujishige 《Mathematical Programming》1984,29(2):125-141
The present paper shows that for any submodular functionf on a crossing family
with
, if the polyhedron
is nonempty, then there exist a unique distributive lattice
with
and a unique submodular function
with
such thatB(f) coincides with the base polyhedron
associated with the submodular system
. Here, iff is integer-valued, thenf
1 is also integer-valued.
Based on this fact, we also show the relationship between the independent-flow problem considered by the author and the minimum
cost flow problem considered by J. Edmonds and R. Giles. 相似文献
8.
Takaaki Nomura 《Annals of Global Analysis and Geometry》1994,12(1):237-260
We study the set of rankp idempotents in a topologically simple Hilbert Jordan algebra (JH-algebra for short). To produce the differential geometric structure on, we establish Jordan algebraic results concerning the structure of some two-generator subalgebras. We identify geodesics, the Riemannian distance and the sectional curvature of by using the Jordan algebraic structure. 相似文献
9.
It
and
are two families of pairwise disjoint simple closed curves in the plane such that each curve in
intersects each curve in
, then the total number of points of intersection in
is at least 2(m−1)n, where
, and this bound is best possible. We use this to show that the cartesian product of two 5-cycles has crossing number 15. 相似文献
10.
Given a self-concordant barrier function for a convex set
, we determine a self-concordant barrier function for the conic hull
of
. As our main result, we derive an “optimal” barrier for
based on the barrier function for
. Important applications of this result include the conic reformulation of a convex problem, and the solution of fractional
programs by interior-point methods. The problem of minimizing a convex-concave fraction over some convex set can be solved
by applying an interior-point method directly to the original nonconvex problem, or by applying an interior-point method to
an equivalent convex reformulation of the original problem. Our main result allows to analyze the second approach showing
that the rate of convergence is of the same order in both cases. 相似文献
11.
K. R. Apt 《Israel Journal of Mathematics》1978,29(2-3):221-238
The connections between inductive definability and models of comprehension are studied. Let
= 〈A, R
l, ...,R
n 〉 be an infinite structure and letI
φ
be a set inductively defined by a formulaφ of the second order language
. We prove that if
is a model of Δ
1
1
-Comprehension relativized toφ, andφ is
-absolute, then for everyη smaller than the height of
(h(
)),I
φ
is in
. If
is aβ-structure which satisfies Σ
1
1
-Comprehension relativized toφ and WF(X), and φ is
-absolute, thenI
φ
is in
and ‖φ| <h (
). These results imply that Barwise-Grilliot theorem is false in the case of uncountable acceptable structures. We also study
the notion of invariant definability over models1 of Δ
1
1
-Comprehension.
This paper is registered as Report ZW 69/76 of the Mathematical Centre. 相似文献
12.
For an arbitrary uniformly continuous completely positive semigroup (
t
:t0) on the space of bounded operators on a Hilbert space, we construct a family (U(t)t0) of unitary operators on a Hilbert space and a conditional expectation from to, such that, for arbitraryt0,. The unitary operatorsU(t) satisfy a stochastic differential equation involving a noncommutative generalisation of infinite dimensional Brownian motion. They do not form a semigroup.Part of this work was completed when the first author was visiting research associate at the Center for Relativity, Physics Department, The University of Texas at Austin, Austin, TX 78712, U.S.A., supported in part by NSF PHY 81-01381. 相似文献
13.
Jean-Eric Pin 《Semigroup Forum》1980,20(1):11-47
Résumé On étudie le mono?de des parties
d'un mono?de fini M. On montre en particulier que pour tout groupe non commutatif fini G et pour tout mono?de fini M, il
existe un entier n tel que M divise
où Gn=G×G×...×G (n fois). Les résultats obtenus permettent d'autre part de décrire toutes les variétés de langages (au sens d'Eilenberg)
qui sont fermées par morphisme littéral (resp. par substitution inverse). On étudie également les variétés fermées par mélange. 相似文献
14.
E. Steingrímsson 《Discrete and Computational Geometry》1994,12(1):465-479
The 2-weak vertex-packing polytope of a loopless graphG withd vertices is the subset of the unitd-cube satisfyingx
i
+x
j
≤1 for every edge (i,j) ofG. The dilation by 2 of this polytope is a polytope
with integral vertices. We triangulate
with lattice simplices of minimal volume and label the maximal simplices with elements of the hyperoctahedral groupB
d
. This labeling gives rise to a shelling of the triangulation
of
, where theh-vector of
(and the Ehrharth
*-vector of
can be computed as a descent statistic on a subset ofB
d
defined in terms ofG. A recursive way of computing theh-vector of
is also given, and a recursive formula for the volume of
.
This work was partially supported by grants from the Icelandic Council of Science and the Royal Swedish Academy of Sciences,
respectively. 相似文献
15.
R. Schneider 《Discrete and Computational Geometry》1995,13(1):609-627
Let
be an infinite discrete system ofk-dimensional flats inn-dimensional Euclidean space. If the totalk-dimensional volume of the flats in
intersected with the ball of center 0 and radiusr, divided by the volume of that ball, tends to a limit forr→∞, then this limit is called thedensity of
. We consider isoperimetric problems of the following kind. If
is a hyperplane system of positive density, find sharp upper bounds for the density of the system ofk-flats (k∈{0, ...,n−2}) that are generated as intersections of hyperplanes in
. Ideas from the theory of uniform distribution of sequences are employed to define a large class of hyperplane systems, calleduniform, for which all necessary densities exist, isperimetric inequalities can be proved, and systems with extremal intersection
densities can be characterized. 相似文献
16.
Let
be a family of two-valued functions defined on ann-element set in which each pair of functions in
satisfy a given intersection condition. For certain intersection conditions we determine the maximal value of
. 相似文献
17.
N. A. Shirokov 《Journal of Mathematical Sciences》1985,31(1):2746-2748
An important condition for the coincidence of the algebras R(E) and C(E) on a compactum was found by A. G. Vitushkin. In this note we give a simple proof of Vitushkin's theorem.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 135, pp. 178–181, 1984. 相似文献
18.
With “hat” denoting the Banach envelope (of a quasi-Banach space) we prove that
if 0<p<1, 0<q<1, ℝ, while
if 0<p<1, 1≤q<+∞, ∝, and
if 1≤p<+∞, 0<q<1, ℝ.
Applications to questions regarding the global interior regularity of solutions to Poisson type problems for the three-dimensional
Lamé system in Lipschitz domains are presented. 相似文献
19.
20.
Summary A state-constrained, nonlinear, minimum problem is considered with dynamics depending sublinearly on a control which is not
bounded in theL
1 norm. Because of the lack of coercivity, the value map
fails to be continuous, even in the unconstrained case. However, we prove that under suitable assumptions—which guarantee
the continuity of the value maps of the problems withL
1-bounded controls—the value map
is upper semicontinuous and solves a Bellman equation with a continuous Hamiltonian. Moreover, the map
obtained by
by replacing its values at the horizon t=T with the values of the cost function turns out to be the maximal subsolution of
the corresponding value problem.
Entrata in Redazione il 31 dicembre 1997. 相似文献