On degree sequences of undirected, directed, and bidirected graphs
نویسندگان
چکیده
منابع مشابه
On degree sequences of undirected, directed, and bidirected graphs
Bidirected graphs generalize directed and undirected graphs in that edges are oriented locally at every node. The natural notion of the degree of a node that takes into account (local) orientations is that of net-degree. In this paper, we extend the following four topics from (un)directed graphs to bidirected graphs: – Erdős–Gallai-type results: characterization of net-degree sequences, – Havel...
متن کاملReduction Factors of Pyramids on Undirected and Directed Graphs
We present two new methods to determine contraction kernels for the construction of graph pyramids. The first method is restricted to undirected graphs and yields a reduction factor of at least . This means that with our method the number of vertices in the subgraph induced by any set of contractible edges is reduced to half or less by a single parallel contraction. Our second method also works...
متن کاملEndomorphisms of undirected modifications of directed graphs
If z is an automorphism (or an endomorphism) of H, then it is also an automorphism (or an endomorphism) of %H and of %H. Hence the automorphism group Aut H is a subgroup of Aut 9?H and of Aut %H. Is there any other relation between the groups Aut H, Aut CBH and Aut %H? More in detail, which spans of groups, see Fig. 1, where m,, m2 are monomorphisms, can be realized by directed graphs H (in the...
متن کاملAlgorithms for realizing degree sequences of directed graphs
The Havel-Hakimi algorithm for constructing realizations of degree sequences for undirected graphs has been used extensively in the literature. A result by Kleitman and Wang extends the Havel-Hakimi algorithm to degree sequences for directed graphs. In this paper we go a step further and describe a modification of Kleitman and Wang’s algorithm that is a more natural extension of Havel-Hakimi’s ...
متن کاملAn Overview of the Degree/Diameter Problem for Directed, Undirected and Mixed Graphs
A well-known fundamental problem in extremal graph theory is the degree/diameter problem, which is to determine the largest (in terms of the number of vertices) graphs or digraphs or mixed graphs of given maximum degree, respectively, maximum outdegree, respectively, mixed degree; and given diameter. General upper bounds, called Moore bounds, exist for the largest possible order of such graphs,...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: European Journal of Combinatorics
سال: 2017
ISSN: 0195-6698
DOI: 10.1016/j.ejc.2017.04.002