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Zapiski Nauchnykh Seminarov POMI, 2013, Volume 415, Pages 24–28
(Mi znsl5682)
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On the space of convex figures
V. V. Makeev, N. Yu. Netsvetaev St. Petersburg State University, St. Petersburg, Russia
Abstract:
Let T be the set of convex bodies in Rk, and let T be the set of classes of similar bodies in T. We write F for T in the case k=2. Define a metric d on T by setting for classes {K1},{K2} (from T, of convex bodies K1,K2) d({K1},{K2})=inf{ln(b/a)}, where a and b are positive reals such that there is a similarity transformation A with aA(K1)⊂K2⊂bA(K1). Let D2 be a planar unit disk. If x>0, we denote by Fx the set of the planar convex figures K in F with d({D2},{K})⩾x. We also equip the sets T and F with the usual Hausdorff metric.
We prove that if y>ln(sec(π/n))⩾x for some integer n>2, then no mapping Fx→Fy is SO(2)-equivariant.
Let Mk(n) be the space of k-dimensional convex polyhedra with at most n hyperfaces (vertices), and let Mk denote the space of k-dimensional convex polyhedra. We prove that there are no SO(2)-equivariant continuous mappings Mk(n+k)→Mk(n).
Let Ts be the closed subspace of T formed by centrally symmetric bodies. Let Tx denote the closed subspace of T formed by the bodies K with d(Ts,{K})⩾x>0. We prove that for every y>0 there exists an x>0 such that no mapping Tx→Ty is SO(2)-equivariant.
Key words and phrases:
convex figure, convex body, orthogonal group, vector bundle, Grassmannian.
Received: 31.12.2012
Citation:
V. V. Makeev, N. Yu. Netsvetaev, “On the space of convex figures”, Geometry and topology. Part 12, Zap. Nauchn. Sem. POMI, 415, POMI, St. Petersburg, 2013, 24–28; J. Math. Sci. (N. Y.), 212:5 (2016), 533–535
Linking options:
https://www.mathnet.ru/eng/znsl5682 https://www.mathnet.ru/eng/znsl/v415/p24
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Abstract page: | 242 | Full-text PDF : | 59 | References: | 37 |
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