spectral-radius-of-graph.ipynb

Kernel: SageMath (Development)

Compute the spectral radius of a tree with SageMath

Gordon reports an issue at

• Ask Sage question: Why can't I find the spectral radius of a tree?

David opens a ticket at

• SageMath Trac ticket 26148: Infinite loop in spectral_radius for trees

Vincent fixes the issue. David reviews the fix. The fix is merged in Sage 8.4.beta4.

Since CoCalc has the latest development release of SageMath, let's test this!

We open a Jupyter notebook in CoCalc and select the "SageMath (development)" kernel for Jupyter from the Kernel menu.

version()

'SageMath version 8.4.beta4, Release Date: 2018-09-06'

g = graphs.CompleteBipartiteGraph(1, 3)

g.spectral_radius()

(1.7320508075688772, 1.7320508075688772)

It works!