Total Curvature of Graphs in Space
نویسنده
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].
منابع مشابه
Fixed points for total asymptotically nonexpansive mappings in a new version of bead space
The notion of a bead metric space is defined as a nice generalization of the uniformly convex normed space such as $CAT(0)$ space, where the curvature is bounded from above by zero. In fact, the bead spaces themselves can be considered in particular as natural extensions of convex sets in uniformly convex spaces and normed bead spaces are identical with uniformly convex spaces. In this paper, w...
متن کاملRICCI CURVATURE OF SUBMANIFOLDS OF A SASAKIAN SPACE FORM
Involving the Ricci curvature and the squared mean curvature, we obtain basic inequalities for different kind of submaniforlds of a Sasakian space form tangent to the structure vector field of the ambient manifold. Contrary to already known results, we find a different necessary and sufficient condition for the equality for Ricci curvature of C-totally real submanifolds of a Sasakian space form...
متن کاملSpacelike hypersurfaces with constant $S$ or $K$ in de Sitter space or anti-de Sitter space
Let $M^n$ be an $n(ngeq 3)$-dimensional complete connected and oriented spacelike hypersurface in a de Sitter space or an anti-de Sitter space, $S$ and $K$ be the squared norm of the second fundamental form and Gauss-Kronecker curvature of $M^n$. If $S$ or $K$ is constant, nonzero and $M^n$ has two distinct principal curvatures one of which is simple, we obtain some charact...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2006