math1um / objects-invariants-properties

Objects, Invariants and Properties for Graph Theory (GT) automated conjecturing: in particular with the Sage program CONJECTURING: http://nvcleemp.github.io/conjecturing/
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Add isoperimetric_number invariant #628

Open math1um opened 3 years ago

math1um commented 3 years ago

from: Mohar, Bojan. "Isoperimetric numbers of graphs." Journal of combinatorial theory, Series B 47, no. 3 (1989): 274-291.

let delta(U) = the number of edges with one endpoint in U and the other not in U.

isoperimetric_number(U) = min(|delta(U)|/|U|, over all non-empty subsets U of the vertex set V where |U|<=|V|/2)

add this to intractable_invariants list.