Alberto Cavicchioli

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We construct a Heegaard diagram of genus three for the real projective 3-space, which has no waves and pairs of complementary handles. The first example was given by Im and Kim but our diagram has smaller complexity. Furthermore the proof presented here is quite different to that of the quoted authors, and permits also to obtain a simple alternative proof(More)
Let M be a closed connected oriented topological 4-manifold with fundamental group π1. Let Λ be the integral group ring of π1. Suppose that f : M → P is a degree one map inducing an isomorphism on π1. We give a homological condition on the intersection forms λM and λ Λ M under which M is homotopy equivalent to a connected sum P#M ′ for some simply-connected(More)
By An (resp. Nn) we will denote the set {0, 1 , . . . , n} (resp. An-{0}). If X is an arbitrary set, # X means the cardinality of X. All spaces and maps will be in the PL (piecewise-linear) category in the sense of [9] or [15]. The prefix PL will always be omitted. All the spaces that we consider will be compact. For basic graph theory see [8], [6]. The(More)