... in an “unacceptably”smooth Denjoy map and vector field.University of California, Santa Cruz, CA 95064, USAE-mail address: ginzburg@math.ucsc.eduUniversity of California, Santa Cruz, CA, USACurrent ... condition:Iftwo points (a, x), the “entrance”, and (b, y), the “exit”, are on the same characteristic, thenx = y.Inother words, for a characteristic that meets both the bottomand the top of the plug, its ... North-Holland, Amsterdam, 2002.[KH] A. Katok and B. Hasselblatt, Introduction to the Modern Theory of DynamicalSystems, Encyc. of Mathematics and its Applications 54, Cambridge Univ. Press,Cambridge,...