

Other version: http://linkinghub.elsevier.com/retrieve/pii/S0095895698918433
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Not Every Uniform Tree Covers Ramanujan Graphs |
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Published in | Journal of combinatorial theory. Series B. 1998, vol. 74, no. 2, p. 202 - 212 | |
Abstract | The notion of Ramanujan graph has been extended to not necessarily regular graphs by Y. Greenberg. We construct infinite trees with infinitely many finite quotients, none of which is Ramanujan. We give a sufficient condition for a finite graph to be covered by such a tree. | |
Keywords | Ramanujan graph — Covering tree — Spectral radius — Mini- mal graph | |
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Citation (ISO format) | LUBOTZKY, Alexander, SMIRNOVA-NAGNIBEDA, Tatiana. Not Every Uniform Tree Covers Ramanujan Graphs. In: Journal of combinatorial theory. Series B, 1998, vol. 74, n° 2, p. 202 - 212. doi: 10.1006/jctb.1998.1843 https://archive-ouverte.unige.ch/unige:12428 |