Hausdorff tight groupoids generalised

We extend Exel’s ample tight groupoid construction to general locally compact étale groupoids in the Hausdorff case. Moreover, we show how inverse semigroups are represented in this way as ‘pseudobases’ of open bisections, thus yielding a duality which encompasses various extensions of the classic Stone duality.     

局部凸空间中的Drop定理和Phelps引理以及Ekeland变分原理

本文将Drop定理,Phelps引理,Ekeland变分原理和基于Isac的Pareto有效性定理推广到局部完备的局部凸Hausdorff空间,而且证明了它们彼此是等价的．     

Banach Limits of Locally Bounded Real Functions on Hausdorff Spaces

In this paper Banach Limits are studied for locally bounded Lipschitz functions on a Hausdorff space.     

局部凸Hausdorff空间内凝聚选择映象的极大元

在本文内,局部凸Hausdorff空间中凝聚选择映象极大元的两个存在性定理被证明,推广Mehta的最近结果.其中一个定理肯定地解答了Mehta提出的待解决的问题.     

Slim groupoids

Slim groupoids are groupoids satisfying x(yz) ≈ xz. We find all simple slim groupoids and all minimal varieties of slim groupoids. Every slim groupoid can be embedded into a subdirectly irreducible slim groupoid. The variety of slim groupoids has the finite embeddability property, so that the word problem is solvable. We introduce the notion of a strongly nonfinitely based slim groupoid (such groupoids are inherently nonfinitely based) and find all strongly nonfinitely based slim groupoids with at most four elements; up to isomorphism, there are just two such groupoids. The work is a part of the research project MSM0021620839 financed by MSMT.     

Travel groupoids

In this paper, by a travel groupoid is meant an ordered pair (V, *) such that V is a nonempty set and * is a binary operation on V satisfying the following two conditions for all u, v ∈ V:

Lazy groupoids

Semigroup Forum - A binary operation f(x, y) is said to be lazy if every operation that can be obtained from f by composition is equivalent to f(x, y), f(x, x) or x. We...     

Distributive implication groupoids

We introduce a concept of implication groupoid which is an essential generalization of the implication reduct of intuitionistic logic, i.e. a Hilbert algebra. We prove several connections among ideals, deductive systems and congruence kernels which even coincide whenever our implication groupoid is distributive.      

Distributive division groupoids

There are given two equivalent methods to construct BANACH lattices of compact operators. All known examples of such lattices are included.     

Symmetric incidence groupoids

In [7] point-reflection geometries were studied which can be derived from commutative kinematic spaces without involutory elements. But the class of point-reflection geometries is larger. For example, elliptic planes with their reflections cannot be derived from commutative kinematic spaces. Here we investigate a larger class of reflection geometries.This paper was sponsored by Vigoni Program 1999.     

Orbifolds and groupoids

We define a 2-category structure (Pre-Orb) on the category of reduced complex orbifold atlases. We construct a 2-functor F from (Pre-Orb) to the 2-category (Grp) of proper étale effective groupoid objects over the complex manifolds. Both on (Pre-Orb) and (Grp) there are natural equivalence relations on objects: (a natural extension of) equivalence of orbifold atlases on (Pre-Orb) and Morita equivalence in (Grp). We prove that F induces a bijection between the equivalence classes of its source and target.