Tag Archives: buildings

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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Dima Fon-Der-Flaass

Yesterday, Edwin van Dam reminded us of a conjecture he and Willem Haemers made ten years ago: almost all graphs are determined by their spectra. This contrasts with the situation for special classes of graphs such as trees, and indeed … Continue reading

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From the archive, 2

Next up is a document which is just over a quarter-century old, a photocopy of a 26-page handwritten document entitled “On doing geometry in CAYLEY”. The background, as explained in the document, is that John Cannon’s computer algebra system CAYLEY, … Continue reading

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