Proving Connectivity After Removing k Vertices in a Finite Graph

In summary, the conversation discussed how to show that a finite connected graph with minimal degree k has a path of length k-1 that can be removed without disconnecting the graph. This can be demonstrated through an induction argument by first removing a vertex from a spanning tree and then finding the 'right' vertex to remove in order to maintain connectivity.
  • #1
Office_Shredder
Staff Emeritus
Science Advisor
Gold Member
5,663
1,566

Homework Statement



If a finite connected graph G has minimal degree k, show there exists a path [tex] x_1, x_2, x_3,..., x_k[/tex] so that [tex]G-{x_1,x_2,...,x_k}[/tex] 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)
 
Physics news on Phys.org
  • #2
: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 ...
 
  • #3
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
 
Last edited by a moderator:

FAQ: Proving Connectivity After Removing k Vertices in a Finite Graph

1. What is a finite graph?

A finite graph is a mathematical structure consisting of a set of vertices and a set of edges connecting these vertices, where both the vertices and edges are finite in number. It is used to represent relationships or connections between objects or entities.

2. How is connectivity defined in a finite graph?

Connectivity in a finite graph refers to the ability to travel from one vertex to another through a series of connected edges. A graph is considered connected if there is a path between every pair of vertices.

3. What does it mean to remove k vertices from a finite graph?

Removing k vertices from a finite graph means to delete k vertices and any edges connected to those vertices from the graph. This alters the graph's structure and can affect its connectivity.

4. What is the significance of proving connectivity after removing k vertices in a finite graph?

Proving connectivity after removing k vertices is important because it helps determine if the graph remains connected even after the removal of a certain number of vertices. This can have implications in various fields, such as computer science and network analysis.

5. How is the connectivity of a finite graph after removing k vertices proven?

To prove connectivity after removing k vertices in a finite graph, one can use various methods such as induction, contradiction, or graph theory theorems. These techniques involve analyzing the remaining graph structure and determining if there is still a path between all pairs of vertices.

Back
Top