Excluding a small minor

There are sixteen 3-connected graphs on eleven or fewer edges. For each of these graphs H we discuss the structure of graphs that do not contain a minor isomorphic to H. © 2012 Elsevier B.V. All rights reserved

A chain theorem for 3 \u3csup\u3e+\u3c/sup\u3e-connected graphs

A 3-connected graph is called 3 +-connected if it has no 3-separation that separates a large fan or K 3,n from the rest of the graph. It is proved in this paper that except for K 4, every 3 +-connected graph has a 3 +-connected proper minor that is at most two edges away from the original graph. This result is used to characterize Q-minor-free graphs, where Q is obtained from the cube by contracting an edge. © 2012 Society for Industrial and Applied Mathematics

Lepton-Flavor Violating Processes li→ljγl_{i}\to l_{j}\gamma in Topcolor Assisted Technicolor Models

We consider the lepton-flavor violating(LFV) processes $l_{i}\to l_{j}\gamma$ in the framework of topcolor assisted technicolor(TC2) models. We find that the new gauge boson $Z^{\prime}$ predicted by TC2 models can give significantly contributions to these processes via the flavor changing couplings. The present experimental bound on the LFV process $\mu \to e\gamma$ gives severe constraints on the TC2 models. In the case that the $Z^{\prime}$ mass $M_{Z}$ is consistent with other experimental constraints, we obtain constraints on the lepton mixing factors $K_{\tau\mu}$ and $K_{\tau e}$. The future LFV experiments will be probe of the TC2 models.Comment: some mistakes corrected and several references adde