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Displaying 101 – 120 of 152

Homomorphism duality for rooted oriented paths

Petra Smolíková (2000)

Commentationes Mathematicae Universitatis Carolinae

Let $(H, r)$ be a fixed rooted digraph. The $(H, r)$ -coloring problem is the problem of deciding for which rooted digraphs $(G, s)$ there is a homomorphism $f : G \to H$ which maps the vertex $s$ to the vertex $r$ . Let $(H, r)$ be a rooted oriented path. In this case we characterize the nonexistence of such a homomorphism by the existence of a rooted oriented cycle $(C, q)$ , which is homomorphic to $(G, s)$ but not homomorphic to $(H, r)$ . Such a property of the digraph $(H, r)$ is called rooted cycle duality or $*$ -cycle duality. This extends the analogical result for...

Homomorphisms and related contractions of graphs.

Girse, Robert D., Gillman, Richard A. (1988)

International Journal of Mathematics and Mathematical Sciences

Homomorphisms of complete n-partite graphs.

Girse, Robert D. (1986)

International Journal of Mathematics and Mathematical Sciences

Homomorphisms of finite bipartite graphs onto complete bipartite graphs

Bohdan Zelinka (1982)

Mathematica Slovaca

Homomorphisms of Graphs and of Their Orientations.

P. Hell, J. Nesetril (1978)

Monatshefte für Mathematik

Homomorphisms of infinite bipartite graphs onto complete bipartite graphs

Bohdan Zelinka (1983)

Czechoslovak Mathematical Journal

Homomorphisms of nets of fixed degree, with singular points on the same line

Václav Havel (1976)

Czechoslovak Mathematical Journal

Homomorphisms of triangle groups with large injectivity radius.

Abas, M. (2003)

Acta Mathematica Universitatis Comenianae. New Series

Homopolar circuits in polar graphs

Lars Døvling Andersen, Douglas D. Grant (1981)

Czechoslovak Mathematical Journal

Homotopy and homology in pretopological spaces

Demaria, Davide Carlo, Bogin, Garbaccio Rosanna (1984)

Proceedings of the 11th Winter School on Abstract Analysis

Homotopy equivalence of isospectral graphs.

Bisson, Terrence, Tsemo, Aristide (2011)

The New York Journal of Mathematics [electronic only]

Homotopy types of line arrangements.

Michael Falk (1993)

Inventiones mathematicae

Honeycomb arrays.

Blackburn, Simon R., Panoui, Anastasia, Paterson, Maura B., Stinson, Douglas R. (2010)

The Electronic Journal of Combinatorics [electronic only]

Hook length formula and geometric combinatorics.

Pak, Igor (2001)

Séminaire Lotharingien de Combinatoire [electronic only]

Hook length formulas for trees by Han's expansion.

Chen, William Y.C., Gao, Oliver X.Q., Guo, Peter L. (2009)

The Electronic Journal of Combinatorics [electronic only]

Hook lengths in a skew Young diagram.

Janson, Svante (1997)

The Electronic Journal of Combinatorics [electronic only]

Hooks and powers of parts in partitions.

Bacher, Roland, Manivel, Laurent (2002)

Séminaire Lotharingien de Combinatoire [electronic only]

Hopf algebras and dendriform structures arising from parking functions

Jean-Christophe Novelli, Jean-Yves Thibon (2007)

Fundamenta Mathematicae

We introduce a graded Hopf algebra based on the set of parking functions (hence of dimension ${(n + 1)}^{n - 1}$ in degree n). This algebra can be embedded into a noncommutative polynomial algebra in infinitely many variables. We determine its structure, and show that it admits natural quotients and subalgebras whose graded components have dimensions respectively given by the Schröder numbers (plane trees), the Catalan numbers, and powers of 3. These smaller algebras are always bialgebras and belong to some family...

Horocyclic products of trees

Laurent Bartholdi, Markus Neuhauser, Wolfgang Woess (2008)

Journal of the European Mathematical Society

Let $T_{1}, \dots, T_{d}$ be homogeneous trees with degrees $q_{1} + 1, \dots, q_{d} + 1 \geq 3$ , respectively. For each tree, let $𝔥 : T_{j} \to ℤ$ be the Busemann function with respect to a fixed boundary point (end). Its level sets are the horocycles. The horocyclic product of $T_{1}, \dots, T_{d}$ is the graph $𝖣𝖫 (q_{1}, \dots, q_{d})$ consisting of all $d$ -tuples $x_{1} \dots x_{d} \in T_{1} \times \dots \times T_{d}$ with $𝔥 (x_{1}) + \dots + 𝔥 (x_{d}) = 0$ , equipped with a natural neighbourhood relation. In the present paper, we explore the geometric, algebraic, analytic and probabilistic properties of these graphs and their isometry groups. If $d = 2$ and $q_{1} = q_{2} = q$ then we obtain a Cayley graph of the...

Hosoya polynomial of Hanoi graphs

Kishori P. Narayankar, S. B. Lokesh, Veena Mathad, Ivan Gutman (2012)

Kragujevac Journal of Mathematics

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