Conjecture on the limiting probability that a random lift is Ramanujan
Conjecture on the limiting probability that a random lift is Ramanujan
Let be a Ramanujan graph, and let be its random uniform -lift. A graph is Ramanujan when all its nontrivial eigenvalues have absolute value at most the Ramanujan bound for a -regular graph.
Ramanujan-lift probability conjecture. There exists a constant with such that
where the term tends to as . This predicts that the probability of the Ramanujan property for random lifts converges to a nontrivial limit, rather than to either zero or one. The source presents this as a natural conjecture motivated by the unresolved probability that a random regular graph is Ramanujan; no resolution status is given.
Sources & referencesView supporting material
Primary source
Eyal Lubetzky, Benny Sudakov and Van Vu, “Spectra of lifted Ramanujan graphs”, arXiv:0911.4148 (2009).
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