eng Some non-amenable groups Kar, Aditi Niblo, Graham A. info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 2012 Finitely generated groups Orbifolds Cohomology Euler characteristic Publicacions matemàtiques http://ddd.uab.cat/record/85173 oai:ddd.uab.cat:85173 02141493v56n1p255 10.5565/PUBLMAT_56112_09 Tots els drets reservats http://www.europeana.eu/rights/rr-f/ We generalise a result of R. Thomas to establish the non-vanishing of the first L2 Betti number for a class of nitely generated groups.