Proving Connectivity After Removing k Vertices in a Finite Graph

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SUMMARY

The discussion centers on proving that in a finite connected graph G with a minimal degree of k, it is possible to find a path of length k such that removing k vertices from G maintains its connectivity. The user explores an inductive approach, demonstrating that removing a leaf from a spanning tree keeps the graph connected, thus allowing for the removal of additional vertices. The challenge lies in identifying the correct vertices to remove to ensure the existence of a path of the required length.

PREREQUISITES
  • Understanding of graph theory concepts, particularly minimal degree and connectivity.
  • Familiarity with induction proofs in mathematical reasoning.
  • Knowledge of spanning trees and their properties.
  • Ability to analyze paths and edges within a graph structure.
NEXT STEPS
  • Study the properties of spanning trees in graph theory.
  • Learn about induction techniques specifically applied to graph connectivity proofs.
  • Explore algorithms for finding paths in graphs, such as Depth-First Search (DFS).
  • Investigate the implications of vertex removal on graph connectivity and minimal degree.
USEFUL FOR

This discussion is beneficial for students and researchers in graph theory, particularly those studying connectivity and vertex properties in finite graphs. It is also useful for educators preparing materials on inductive proofs and graph algorithms.

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Homework Statement



If a finite connected graph G has minimal degree k, show there exists a path x_1, x_2, x_3,..., x_k so that G-{x_1,x_2,...,x_k} is still connected

Homework Equations



Minimal degree means every vertex has k or more edges connecting to it

The Attempt at a Solution



I'm pretty much nowhere. I can do by induction that you can remove k vertices without disconnecting G by the following:

You can pare G down to a spanning tree, and then it has a vertex you can remove from the tree (since it has to have a leaf). Remove that, and the tree is still connected, so when you add back the rest of the edges it's still connected. This new graph has minimal degree at least k-1 so there are k-1 other vertices you can remove.

I can't see how to make a path though (I tried a similar induction argument for a path but it's demonstrably false as far as I can tell)
 
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:rolleyes: I think this is silly.

:rolleyes: It has taken me since yesterday to realize. :redface:

If you can show, similarly to what you have, that you can remove an edge, x1 say, without disconnecting, then you have a connected graph G - x1 of minimal degree (k -1), so ...
 
So I can remove a path of length k-1. I have already demonstrated to myself that the path found is not necessarily one that can be extended to a path of length k, unless I missed something.

http://img21.imageshack.us/img21/8876/graphtheory.png

I need a way of finding the 'right' vertex to remove, so that a path can be removed of length k-1 that has an edge to the one I removed.

EDIT: Whoops, the graph in the picture has minimal degree k, not k+1. That's a typo
 
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