INTERSECTING the SIDES of A POLYGON

Research output: Contribution to journalArticlepeer-review

Abstract

Consider the map S which sends a planar polygon P to a new polygon S(P) whose vertices are the intersection points of second-nearest sides of P. This map is the inverse of the famous pentagram map. In this paper we investigate the dynamics of the map S. Namely, we address the question of whether a convex polygon stays convex under iterations of S. Computer experiments suggest that this almost never happens. We prove that indeed the set of polygons which remain convex under iterations of S has measure zero, and moreover it is an algebraic subvariety of codimension two. We also discuss the equations cutting out this subvariety, as well as their geometric meaning in the case of pentagons.

Original languageEnglish (US)
Pages (from-to)639-649
Number of pages11
JournalProceedings of the American Mathematical Society
Volume150
Issue number2
DOIs
StatePublished - 2022

ASJC Scopus subject areas

  • Mathematics(all)
  • Applied Mathematics

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