Tag Archives: Laci Babai

Asymptotic group theory, 3

A Ramanujan graph is a connected finite graph of valency k whose eigenvalues (apart from k and −k) all have modulus at most 2√(k−1). This interval is the spectrum of the infinite k-valent tree T (regarded as an operator on … Continue reading

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Automorphism groups of hypergraphs

I am getting old and forgetful, but I don’t think I said anything here about this problem yet. If I did, apologies for the repetition – but there is something new to report! In April, Laci Babai and I finally … Continue reading

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