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81.
Tanya Schmah 《Proceedings of the American Mathematical Society》2001,129(4):1169-1177
Which -dimensional orbi-spaces have effective symplectic - torus actions? As shown by Lerman and Tolman (1997) and Watson (1997), this question reduces to that of characterizing the finite subgroups of centralizers of tori in the real symplectic group . We resolve this question, and generalize our method to a calculation of the centralizers of all tori in .
82.
Daniel Daigle Gene Freudenburg 《Proceedings of the American Mathematical Society》2001,129(3):657-662
For a field of characteristic zero, and for each integer , we construct a triangular derivation of whose ring of constants, though finitely generated over , cannot be generated by fewer than elements.
83.
Let G be a complex semisimple group with real form G
. For the action of G
× G
on G by left and right translation, we define and study an orbit-type stratification of G. In particular, we compute the dimension of an arbitrary stratum; we identify certain strata of low codimension in G, the union of whose closures contains every nonprincipal stratum; and we describe the boundaries and adjacency relations of the maximal connected domains in G that contain only principal orbits. 相似文献
84.
Elias Gabriel Minian 《K-Theory》2000,20(1):37-95
We develop an axiomatic homotopy theory for categories with a family of natural cylinders indexed by a set with relations, generalizing Baues I-categories. The main examples of -cofibration categories are the categories of global actions and simplicial complexes. 相似文献
85.
Nathan L. Harshman 《International Journal of Theoretical Physics》2007,46(8):1929-1946
The notion that elementary systems correspond to irreducible representations of the Poincaré group is the starting point for
this paper, which then goes on to discuss how a semigroup for the time evolution of unstable states and resonances could emerge
from the underlying Poincaré symmetry. Important tools in this analysis are the Clebsch-Gordan coefficients for the Poincaré
group. 相似文献
86.
Jitender Kumar 《代数通讯》2013,41(12):5152-5169
In order to study the structure of A +(B n )—the affine near-semiring over a Brandt semigroup—this work completely characterizes the Green's classes of its semigroup reducts. In this connection, this work classifies the elements of A +(B n ) and reports the size of A +(B n ). Further, idempotents and regular elements of the semigroup reducts of A +(B n ) have also been characterized and studied some relevant semigroups in A +(B n ). 相似文献
87.
A. Vasiu 《Mathematische Nachrichten》2010,283(8):1068-1113
Let k be an algebraically closed field of positive characteristic p. We first classify the D ‐truncations mod p of Shimura F ‐crystals over k and then we study stratifications defined by inner isomorphism classes of these D ‐truncations. This generalizes previous works of Kraft, Ekedahl, Oort, Moonen, and Wedhorn. As a main tool we introduce and study Bruhat F ‐decompositions; they generalize the combined form of Steinberg theorem and of classical Bruhat decompositions for reductive groups over k (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
88.
Nándor Sieben 《Czechoslovak Mathematical Journal》2008,58(3):683-692
The notion of Cayley color graphs of groups is generalized to inverse semigroups and groupoids. The set of partial automorphisms
of the Cayley color graph of an inverse semigroup or a groupoid is isomorphic to the original inverse semigroup or groupoid.
The groupoid of color permuting partial automorphisms of the Cayley color graph of a transitive groupoid is isomorphic to
the original groupoid. 相似文献
89.
In this paper we study sub-semigroups of a finite or an infinite zero-divisor semigroup S determined by properties of the zero-divisor graph Γ(S). We use these sub-semigroups to study the correspondence between zero-divisor semigroups and zero-divisor graphs. In particular, we discover a class of sub-semigroups of reduced semigroups and we study properties of sub-semigroups of finite or infinite semilattices with the least element. As an application, we provide a characterization of the graphs which are zero-divisor graphs of Boolean rings. We also study how local property of Γ(S) affects global property of the semigroup S, and we discover some interesting applications. In particular, we find that no finite or infinite two-star graph has a corresponding nil semigroup. 相似文献
90.
Let g
e
(S) (respectively, g
o
(S)) be the number of even (respectively, odd) gaps of a numerical semigroup S. In this work we study and characterize the numerical semigroups S that verify 2|g
e
(S)−g
o
(S)|+1∈S. As a consequence we will see that every numerical semigroup can be represented by means of a numerical semigroup with maximal
embedding dimension with all its minimal generators odd.
The first author is supported by the project MTM2007-62346 and FEDER funds. The authors want to thank P.A. García-Sánchez
and the referee for their comments and suggestions. 相似文献