%0 Journal Article %1 lubotzky98 %A Lubotzky, Alexander %A Nagnibeda, Tatiana %D 1998 %J Journal of Combinatorial Theory, Series B %K eigenvalues expander graph.theory ramanujan %N 2 %P 202--212 %R 10.1006/jctb.1998.1843 %T Not Every Uniform Tree Covers Ramanujan Graphs %V 74 %X 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.

@article{lubotzky98, 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.}, added-at = {2016-10-29T16:17:57.000+0200}, author = {Lubotzky, Alexander and Nagnibeda, Tatiana}, biburl = {https://www.bibsonomy.org/bibtex/2231a1144a8b42475e3cc801ac943b5c8/ytyoun}, doi = {10.1006/jctb.1998.1843}, interhash = {a6719f411cba91ac1cfb80ab38aa0a33}, intrahash = {231a1144a8b42475e3cc801ac943b5c8}, issn = {0095-8956}, journal = {Journal of Combinatorial Theory, Series B}, keywords = {eigenvalues expander graph.theory ramanujan}, number = 2, pages = {202--212}, timestamp = {2017-02-23T12:42:13.000+0100}, title = {Not Every Uniform Tree Covers Ramanujan Graphs}, volume = 74, year = 1998 }