Total Curvature of Graphs in Space

نویسنده

  • ROBERT GULLIVER
چکیده

The Fáry-Milnor Theorem says that any embedding of the circle S1 into R3 of total curvature less than 4π is unknotted. More generally, a (finite) graph consists of a finite number of edges and vertices. Given a topological type of graphs Γ, what limitations on the isotopy class of Γ are implied by a bound on total curvature? Especially: what does “total curvature” mean for a graph? I shall discuss several natural notions of the total curvature of a graph. Turning to the problem of isotopy type, I shall then focus on the notion of net total curvature N (Γ) of a graph Γ ⊂ R3, and outline the proof that if Γ is homeomorphic to the θ-graph, thenN (Γ) ≥ 3π; and ifN (Γ) < 4π, then Γ is isotopic in R3 to a planar θ-graph. Proofs will be given in full in [GY2].

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تاریخ انتشار 2006