Midgap states in corrugated graphene: Ab initio calculations and effective field theory T. O. Wehling, A. V. Balatsky, A. M. Tsvelik, M. I. Katsnelson and A. I. Lichtenstein EPL, 84 1 (2008) 17003 Published online: 18 September 2008 DOI: 10.1209/0295-5075/84/17003