The topology of normal singularities of an algebraic surface

Friedrich Hirzebruch

Displaying similar documents to “The topology of normal singularities of an algebraic surface”

Constructions for type I trees with nonisomorphic Perron branches

Stephen J. Kirkland (1999)

Czechoslovak Mathematical Journal

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A tree is classified as being type I provided that there are two or more Perron branches at its characteristic vertex. The question arises as to how one might construct such a tree in which the Perron branches at the characteristic vertex are not isomorphic. Motivated by an example of Grone and Merris, we produce a large class of such trees, and show how to construct others from them. We also investigate some of the properties of a subclass of these trees. Throughout, we exploit connections...

Statuses and branch-weights of weighted trees

Chiang Lin, Jen-Ling Shang (2009)

Czechoslovak Mathematical Journal

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In this paper we show that in a tree with vertex weights the vertices with the second smallest status and those with the second smallest branch-weight are the same.

A combinatorial derivation of the number of labeled forests.

Callan, David (2003)

Journal of Integer Sequences [electronic only]

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On a bound on algebraic connectivity: the case of equality

Stephen J. Kirkland, Neumann, Michael, Bryan L. Shader (1998)

Czechoslovak Mathematical Journal

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In a recent paper the authors proposed a lower bound on $1 - λ_{i}$ , where $λ_{i}$ , $λ_{i} \neq 1$ , is an eigenvalue of a transition matrix $T$ of an ergodic Markov chain. The bound, which involved the group inverse of $I - T$ , was derived from a more general bound, due to Bauer, Deutsch, and Stoer, on the eigenvalues of a stochastic matrix other than its constant row sum. Here we adapt the bound to give a lower bound on the algebraic connectivity of an undirected graph, but principally consider the case of equality in...

The number of isomorphism classes of spanning trees of a graph

Bohdan Zelinka (1978)

Mathematica Slovaca

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Constrained Steiner trees in Halin graphs

Guangting Chen, Rainer E. Burkard (2003)

RAIRO - Operations Research - Recherche Opérationnelle

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In this paper, we study the problem of computing a minimum cost Steiner tree subject to a weight constraint in a Halin graph where each edge has a nonnegative integer cost and a nonnegative integer weight. We prove the NP-hardness of this problem and present a fully polynomial time approximation scheme for this NP-hard problem.