K5 is the only double-critical 5-chromatic graph

نویسندگان

چکیده

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Edge Chromatic 5-Critical Graphs

In this paper, we study the structure of 5-critical graphs in terms of their size. In particular, we have obtained bounds for the number of major vertices in several classes of 5-critical graphs, that are stronger than the existing bounds.

متن کامل

The chromatic numbers of double coverings of a graph

If we fix a spanning subgraph H of a graph G, we can define a chromatic number of H with respect to G and we show that it coincides with the chromatic number of a double covering of G with co-support H. We also find a few estimations for the chromatic numbers of H with respect to G.

متن کامل

The average degree of an edge-chromatic critical graph

A graph G with maximum degree and edge chromatic number ′(G)> is edge-critical if ′(G− e)= for every edge e of G. New lower bounds are given for the average degree of an edge-critical graph, which improve on the best bounds previously known for most values of . Examples of edge-critical graphs are also given. In almost all cases, there remains a large gap between the best lower bound known and ...

متن کامل

On the chromatic number of a random 5-regular graph

It was only recently shown by Shi and Wormald, using the differential equation method to analyse an appropriate algorithm, that a random 5-regular graph asymptotically almost surely has chromatic number at most 4. Here, we show that the chromatic number of a random 5-regular graph is asymptotically almost surely equal to 3, provided a certain four-variable function has a unique maximum at a giv...

متن کامل

Group Chromatic Number of Graphs without K5-Minors

Let G be a graph with a ®xed orientation and let A be a group. Let F …G; A† denote the set of all functions f : E…G† U 3 A. The graph G is A-colorable if for any function f P F …G; A†, there is a function c: V …G† U 3 A such that for every directed e ˆ uv P E…G†, c…u† À c…v† T ˆ f …e†. The group chromatic number v 1 …G† of a graph G is the minimum m such that G is A-colorable for any group A of...

متن کامل

ذخیره 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: Discrete Mathematics

سال: 1987

ISSN: 0012-365X

DOI: 10.1016/0012-365x(87)90242-1