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.
Original language | English |
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Pages (from-to) | 202-212 |
Number of pages | 11 |
Journal | Journal of Combinatorial Theory. Series B |
Volume | 74 |
Issue number | 2 |
DOIs | |
State | Published - Nov 1998 |
Keywords
- Covering tree
- Minimal graph
- Ramanujan graph
- Spectral radius