starlike tree

On Lower Bound of Edge Number of Minimal Edge 1-Extension of Starlike Tree

Authors: Abrosimov M. B.

For a given graph G with n nodes, we say that graph G∗ is its 1-edge extension if for each edge e of G∗ the subgraph G∗ −e contains graph G up to isomorphism. Graph G∗ is minimal 1-edge extension of graph G if G∗ has n nodes and there is no 1-edge extension with n nodes of graph G having fewer edges than G. A tree is called starlike if it has exactly one node of degree greater than two. We give a lower bound of edge number of minimal edge 1-extension of starlike tree and provide family on which this bound is achieved.

Indices of States in Dynamical System of Binary Vectors Associated with Palms Orientations

Authors: Zharkova A. V.

Dynamical system of binary vectors associated with palms orientations is considered. A tree is called a palm with s + c edges if it is a union of c + 1 paths with common end vertex and all of these paths except perhaps one (with s edges) have a length 1. The system splits into finite subsystems according to the dimension of states. States of a finite dynamical system (B s+c ,γ) are all possible orientations of a given palm with s + c edges.

T-irreducible Extensions for Starlike Trees

Authors: Osipov D. Y.

We deal with a sort of optimal extensions of graphs, so called T-irreducible extensions. T-irreducible extension of a graph G is an extension of G obtained by removing a maximal set of edges from the trivial extension of G. A difficult starlike tree is a starlike tree that has at least one difficult node. T-irreducible extensions for nondifficult starlike trees were constructed by M. B. Abrosimov, T-irreducible extensions for palms (one of subclasses of starlike trees) were constructed by S. G. Kurnosova.