New Proof Settles Decades-Old Bet About Connected Networks

It started with a bet. In the late 1980s, at a conference in Lausanne, the mathematicians Noga Alon and Peter Sarnak got into a friendly debate. Both were studying collections of nodes and edges called graphs. In particular, they wanted to better understand a paradoxical type of graph, called an expander, that has relatively few edges but is still highly interconnected. At issue were the very…
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