Counting Periodic Trajectories of Finsler Billiards

We provide lower bounds on the number of periodic Finsler billiard trajectories inside a quadratically convex smooth closed hypersurface M in a 𝑑-dimensional Finsler space with possibly irreversible Finsler metric. An example of such a system is a billiard in a sufficiently weak magnetic field. The...

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Published in:Symmetry, Integrability and Geometry: Methods and Applications
Date:2020
Main Authors: Blagojević, Pavle V.M., Harrison, Michael, Tabachnikov, Serge, Ziegler, Günter M.
Format: Article
Language:English
Published: Інститут математики НАН України 2020
Online Access:https://nasplib.isofts.kiev.ua/handle/123456789/210588
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Journal Title:Digital Library of Periodicals of National Academy of Sciences of Ukraine
Cite this:Counting Periodic Trajectories of Finsler Billiards. Pavle V.M. Blagojević, Michael Harrison, Serge Tabachnikov and Günter M. Ziegler. SIGMA 16 (2020), 022, 33 pages

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Digital Library of Periodicals of National Academy of Sciences of Ukraine
id nasplib_isofts_kiev_ua-123456789-210588
record_format dspace
spelling Blagojević, Pavle V.M.
Harrison, Michael
Tabachnikov, Serge
Ziegler, Günter M.
2025-12-12T10:31:40Z
2020
Counting Periodic Trajectories of Finsler Billiards. Pavle V.M. Blagojević, Michael Harrison, Serge Tabachnikov and Günter M. Ziegler. SIGMA 16 (2020), 022, 33 pages
1815-0659
2020 Mathematics Subject Classification: 37J45; 55R80; 70H12
arXiv:1712.07930
https://nasplib.isofts.kiev.ua/handle/123456789/210588
https://doi.org/10.3842/SIGMA.2020.022
We provide lower bounds on the number of periodic Finsler billiard trajectories inside a quadratically convex smooth closed hypersurface M in a 𝑑-dimensional Finsler space with possibly irreversible Finsler metric. An example of such a system is a billiard in a sufficiently weak magnetic field. The 𝑟-periodic Finsler billiard trajectories correspond to 𝑟-gons inscribed in M and having extremal Finsler length. The cyclic group ℤᵣ acts on these extremal polygons, and one counts the ℤᵣ-orbits. Using Morse and Lusternik-Schnirelmann theories, we prove that if 𝑟 ≥ 3 is prime, then the number of 𝑟-periodic Finsler billiard trajectories is not less than (𝑟−1)(𝑑−2)+1. We also give stronger lower bounds when M is in general position. The problem of estimating the number of periodic billiard trajectories from below goes back to Birkhoff. Our work extends to the Finsler setting, the results previously obtained for Euclidean billiards by Babenko, Farber, Tabachnikov, and Karasev.
We are grateful to Sergei Ivanov for useful discussions on Finsler geometry, and we are grateful to the following sources of funding. Pavle V. M. Blagojevic, Serge Tabachnikov, and Gunter M. Ziegler were supported by the DFG via the Collaborative Research Center TRR 109 Discretization in Geometry and Dynamics. Pavle V. M. Blagojevic was supported by the grant ON 174024 of the Serbian Ministry of Education and Science. Michael Harrison and Serge Tabachnikov were supported by the NSF grant DMS-1510055. We are also grateful to the referees for their suggestions.
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Інститут математики НАН України
Symmetry, Integrability and Geometry: Methods and Applications
Counting Periodic Trajectories of Finsler Billiards
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title Counting Periodic Trajectories of Finsler Billiards
spellingShingle Counting Periodic Trajectories of Finsler Billiards
Blagojević, Pavle V.M.
Harrison, Michael
Tabachnikov, Serge
Ziegler, Günter M.
title_short Counting Periodic Trajectories of Finsler Billiards
title_full Counting Periodic Trajectories of Finsler Billiards
title_fullStr Counting Periodic Trajectories of Finsler Billiards
title_full_unstemmed Counting Periodic Trajectories of Finsler Billiards
title_sort counting periodic trajectories of finsler billiards
author Blagojević, Pavle V.M.
Harrison, Michael
Tabachnikov, Serge
Ziegler, Günter M.
author_facet Blagojević, Pavle V.M.
Harrison, Michael
Tabachnikov, Serge
Ziegler, Günter M.
publishDate 2020
language English
container_title Symmetry, Integrability and Geometry: Methods and Applications
publisher Інститут математики НАН України
format Article
description We provide lower bounds on the number of periodic Finsler billiard trajectories inside a quadratically convex smooth closed hypersurface M in a 𝑑-dimensional Finsler space with possibly irreversible Finsler metric. An example of such a system is a billiard in a sufficiently weak magnetic field. The 𝑟-periodic Finsler billiard trajectories correspond to 𝑟-gons inscribed in M and having extremal Finsler length. The cyclic group ℤᵣ acts on these extremal polygons, and one counts the ℤᵣ-orbits. Using Morse and Lusternik-Schnirelmann theories, we prove that if 𝑟 ≥ 3 is prime, then the number of 𝑟-periodic Finsler billiard trajectories is not less than (𝑟−1)(𝑑−2)+1. We also give stronger lower bounds when M is in general position. The problem of estimating the number of periodic billiard trajectories from below goes back to Birkhoff. Our work extends to the Finsler setting, the results previously obtained for Euclidean billiards by Babenko, Farber, Tabachnikov, and Karasev.
issn 1815-0659
url https://nasplib.isofts.kiev.ua/handle/123456789/210588
citation_txt Counting Periodic Trajectories of Finsler Billiards. Pavle V.M. Blagojević, Michael Harrison, Serge Tabachnikov and Günter M. Ziegler. SIGMA 16 (2020), 022, 33 pages
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