Seven mutually touching infinite cylinders

Bozóki, Sándor and Lee, T-L. and Rónyai, Lajos (2015) Seven mutually touching infinite cylinders. COMPUTATIONAL GEOMETRY-THEORY AND APPLICATIONS, 48 (2). pp. 87-93. ISSN 0925-7721


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We solve a problem of Littlewood: there exist seven infinite circular cylinders of unit radius which mutually touch each other. In fact, we exhibit two such sets of cylinders. Our approach is algebraic and uses symbolic and numerical computational techniques. We consider a system of polynomial equations describing the position of the axes of the cylinders in the 3 dimensional space. To have the same number of equations (namely 20) as the number of variables, the angle of the first two cylinders is fixed to 90 degrees, and a small family of direction vectors is left out of consideration. Homotopy continuation method has been applied to solve the system. The number of paths is about 121 billion, it is hopeless to follow them all. However, after checking 80 million paths, two solutions are found. Their validity, i.e., the existence of exact real solutions close to the approximate solutions at hand, was verified with the alphaCertified method as well as by the interval Krawczyk method. © 2014 Elsevier B.V.

Item Type: Article
Uncontrolled Keywords: Polynomials; Infinite cylinders; System of polynomial equations; Polynomial systems; Infinite circular cylinder; Homotopy continuation methods; Computational technique; Circular cylinders; Touching cylinders; Polynomial system; Homotopy method; Certified solutions; Alpha theory
Subjects: Q Science / természettudomány > QA Mathematics / matematika > QA76 Computer software / programozás
Depositing User: MTMT SWORD
Date Deposited: 15 Feb 2016 13:03
Last Modified: 15 Feb 2016 13:03

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