Vertex Connectivity

Definition

Vertex connectivity is a measure of how well connected the vertices of a graph are. Specifically, it is defined as the minimum number of vertices that need to be removed to disconnect the remaining vertices from each other. This concept is crucial when analyzing the robustness of a network, as higher vertex connectivity indicates greater resilience against failures or attacks.

5 Must Know Facts For Your Next Test

1. A graph is said to be k-connected if its vertex connectivity is at least k, meaning at least k vertices must be removed to disconnect it.
2. If a graph has vertex connectivity equal to 0, it implies that the graph is disconnected from the start.
3. The vertex connectivity of a complete graph with n vertices is n-1, as removing any n-1 vertices still leaves one vertex connected.
4. In bipartite graphs, the vertex connectivity can often be determined by the smaller of the two partition sizes.
5. Understanding vertex connectivity is important in network design, particularly for ensuring reliability in communication systems.

Review Questions

• How does vertex connectivity help in assessing the robustness of a network?
  • Vertex connectivity is crucial for evaluating a network's robustness because it indicates how many nodes can fail before the network becomes disconnected. A higher vertex connectivity means that the network can withstand multiple failures without losing overall connectivity. This measure helps engineers design more resilient networks by ensuring that critical nodes are adequately protected and redundancy is implemented.
• Compare and contrast vertex connectivity with edge connectivity, and explain how they both contribute to understanding graph structure.
  • Vertex connectivity focuses on the minimum number of vertices that must be removed to disconnect the graph, while edge connectivity pertains to the edges necessary for maintaining connectivity. Both measures provide insights into a graph's structure; however, vertex connectivity tends to give more information about the overall resilience of a network since it considers node failures, while edge connectivity highlights the importance of specific connections between nodes. Together, they offer a comprehensive view of a graph's vulnerability and robustness.
• Evaluate how cut-vertices and bridges relate to vertex connectivity and their implications for graph stability.
  • Cut-vertices and bridges are directly related to vertex connectivity as they represent critical points and connections whose removal increases disconnection within the graph. Cut-vertices, when removed, increase the number of components in a graph, directly affecting vertex connectivity. Similarly, bridges play a key role since removing them leads to fragmentation. Understanding these concepts is essential for maintaining graph stability in applications such as transportation networks and communication systems, where preserving connections is vital.

Related terms

Edge Connectivity: The minimum number of edges that need to be removed to disconnect the graph.

Cut-Vertex: A vertex whose removal increases the number of connected components in the graph.

Bridge: An edge whose removal disconnects the graph into two or more components.