Results 211 to 220 of about 816 (251)

Enumeration of Concrete Regular Covering Projections

SIAM Journal on Discrete Mathematics, 1995
Polya's and de Brujin's enumerative methods and the Möbius inversion are employed to derive a formula for counting the isomorphism classes of regular covering projections of a graph.
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Knot Projections and Knot Coverings

1993
In this paper, computer programs are given which draw knot diagrams, knot projections and representations of knot groups into the symmetric group of degree n.
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Projective Planes, Coverings and a Network Problem

Designs, Codes and Cryptography, 2003
This article studies a problem concerning packet switched networks which can be translated into a combinatorial design problem involving \(k\)-arcs in projective planes, 3-dimensional linear codes, the theory of fractional matchings and designs which approximate projective planes. The combinatorial design problem concerns coverings \(C(n,k,r)\).
Bierbrauer J., MARCUGINI, Stefano, PAMBIANCO, Fernanda   +2 more
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On Analytic Coverings of Weighted Projective Spaces

Bulletin of the London Mathematical Society, 1985
We classify the analytic coverings of a weighted projective space \(P=P(Q)\) whose branching sets are unions of the form \(P_{\sin g}\cup H\), where \(P_{\sin g}\) denotes the singular part of P and H is a normal hypersurface in P. It turns out that all such coverings are cyclic and their total spaces are hypersurfaces in suitable weighted projective ...
Dimca, Alexandru, Dimiev, Stancho
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Covering groups and projective representations

1992
In order to deduce Theorem 1.18 from the special case established in the last chapter, we will need to exploit a relationship between characters of tori in G and representations of G. This relationship is most natural when it is formulated in terms of certain coverings of the tori related to “ρ-shifts” for G (see for example Theorem 1.37 or Theorem 6.8
Jeffrey Adams, Dan Barbasch, David A. Vogan   +2 more
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Rings Whose Nonsingular Modules Have Projective Covers

Ukrainian Mathematical Journal, 2016
zbMATH Open Web Interface contents unavailable due to conflicting licenses.
Asgari, Sh., Haghany, A.
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Projective Groups and Frattini Covers

1986
The absolute Galois group of a PAC field is projective (Theorem 10.17). This chapter includes a converse (Corollary 20.16): If G is a projective group, then there exists a PAC field K such that G (K) ≅ G. Projective groups also appear as the universal Frattini covers of profinite groups (Proposition 20.33).
Michael D. Fried, Moshe Jarden
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Directed fibrations and covering projections

Publicationes Mathematicae Debrecen, 2009
Summary: In this note a notion of Hurewicz fibration in the category d{\textbf{Top}} of directed spaces in the sense of \textit{M. Grandis} [Cah. Topol. Géom. Différ. Catég. 44, No.~4, 281--316 (2003; Zbl 1059.55009)] is defined. The directed homotopy lifting property is characterized by means of lifting pairs.
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Projective Covers and Perfect Rings

1976
A morphism f: A → B of R-modules is said to be minimal provided that ker f is a superfluous submodule of A. For example, for a right ideal I, the canonical map R → R/I is superfluous if and only if I ⊆ rad R 18.3. A module A is a projective cover (proj. cov.) of B provided that A is projective and there exists a minimal epimorphism A → B.
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Lecture 7- Projective Modules and Projective Covers

Defines projective modules via the lifting property (equivalently, exactness of Hom_A(P,−)); notes that free modules and their direct summands are projective and that all modules are projective over semisimple rings. Introduces projective indecomposable modules (PIMs) and shows the number of PIMs equals the number of Brauer simples.
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