We prove that the area distance between two convex bodies K and K' with the same parallel X-rays in a set of n mutually non parallel directions is bounded from above by the area of their intersection, times a constant depending only on n. Equality holds if and only if K is a regular n-gon, and K' is K suitably rotated about its center, up to affine transformations. This and similar sharp affine invariant inequalities lead to stability estimates for Hammer's problem if the n directions are known up to an error, or in case X-rays emanating from n collinear points are considered. For n=4, the order of these estimates is compared with the cross ratio of given directions and given points, respectively.
Sharp affine stability estimates for Hammer's problem
DULIO, PAOLO;
2008-01-01
Abstract
We prove that the area distance between two convex bodies K and K' with the same parallel X-rays in a set of n mutually non parallel directions is bounded from above by the area of their intersection, times a constant depending only on n. Equality holds if and only if K is a regular n-gon, and K' is K suitably rotated about its center, up to affine transformations. This and similar sharp affine invariant inequalities lead to stability estimates for Hammer's problem if the n directions are known up to an error, or in case X-rays emanating from n collinear points are considered. For n=4, the order of these estimates is compared with the cross ratio of given directions and given points, respectively.File | Dimensione | Formato | |
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Sharp affine stability estimates for Hammer’s problem.pdf
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