Search results for "rete"

On the boundary spectrum of dominatedC o-Semigroups

1989

Hurwitz spaces of Galois coverings of P1, whose Galois groups are Weyl groups

2006

Abstract We prove the irreducibility of the Hurwitz spaces which parametrize equivalence classes of Galois coverings of P 1 , whose Galois group is an arbitrary Weyl group, and the local monodromies are reflections. This generalizes a classical theorem due to Luroth, Clebsch and Hurwitz.

Computing generators of the tame kernel of a global function field

2006

Abstract The group K 2 of a curve C over a finite field is equal to the tame kernel of the corresponding function field. We describe two algorithms for computing generators of the tame kernel of a global function field. The first algorithm uses the transfer map and the fact that the l -torsion can easily be described if the ground field contains the l th roots of unity. The second method is inspired by an algorithm of Belabas and Gangl for computing generators of K 2 of the ring of integers in a number field. We finally give the generators of the tame kernel for some elliptic function fields.

Positive definite functions of finitary isometry groups over fields of odd characteristic

2007

Abstract This paper is part of a programme to describe the lattice of all two-sided ideals in complex group algebras of simple locally finite groups. Here we determine the extremal normalized positive definite functions for finitary groups of isometries, defined over fields of odd characteristic.

On Finite Solvable Groups That Behave Like Nilpotent Groups with Respect to the Frattini Group

1994

Some criteria for detecting capable Lie algebras

2013

Abstract In virtue of a recent bound obtained in [P. Niroomand, F.G. Russo, A note on the Schur multiplier of a nilpotent Lie algebra, Comm. Algebra 39 (2011) 1293–1297], we classify all capable nilpotent Lie algebras of finite dimension possessing a derived subalgebra of dimension one. Indirectly, we find also a criterion for detecting noncapable Lie algebras. The final part contains a construction, which shows that there exist capable Lie algebras of arbitrary big corank (in the sense of Berkovich–Zhou).

REPRESENTATIVE BRAIDS FOR LINKS ASSOCIATED TO PLANE IMMERSED CURVES

2000

In [ AC 2], A'Campo associates a link in S3 to any proper generic immersion of a disjoint union of arcs into a 2-disc. We give a sample algorithmic way to produce, from the immersion, a representative braid for such links. As a by-product we get a minimal representative braid for any algebraic link, from a divide associated to a real deformation of the polynomial defining the link.

Hybrid bases for varieties of semigroups

2003

We consider the lower part of the lattice of varieties of semigroups. We present finite bases of hybrid identities for the varieties of normal bands, commutative bands and abelian groups of finite exponent. The variety A n,0 of abelian groups provides an example of a variety which has no finite base of hyperidentities (cf. [12]) but has a finite base of hybrid identities.

Identities of PI-Algebras Graded by a Finite Abelian Group

2011

We consider associative PI-algebras over an algebraically closed field of zero characteristic graded by a finite abelian group G. It is proved that in this case the ideal of graded identities of a G-graded finitely generated PI-algebra coincides with the ideal of graded identities of some finite dimensional G-graded algebra. This implies that the ideal of G-graded identities of any (not necessary finitely generated) G-graded PI-algebra coincides with the ideal of G-graded identities of the Grassmann envelope of a finite dimensional (G × ℤ2)-graded algebra, and is finitely generated as GT-ideal. Similar results take place for ideals of identities with automorphisms.

On Shimura subvarieties generated by families of abelian covers ofP1

2018

We investigate the occurrence of Shimura (special) subvarieties in the locus of Jacobians of abelian Galois covers of P1 in Ag and give classifications of families of such covers that give rise to Shimura subvarieties in the Torelli locus Tg inside Ag. Our methods are based on Moonen–Oort works as well as characteristic p techniques of Dwork and Ogus and Monodromy computations.