Capped grope
Introduction In mathematics, a '''grope''' is a construction used in 4-dimensional topology, introduced by  and named by  "because of its multitudinous fingers". Capped gropes were used by  as a substitute for Casson handles, that  work better for non-simply-connected 4-manifolds. A capped surface in a 4-manifold is roughly a surface together with some 2-disks, called caps, whose boundaries generate the fundamental group of the surface. A capped grope is obtained by repeatedly replacing the caps of a capped surface by another capped surface. Capped surfaces and capped  gropes are studied in .
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