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Betweenness isomorphisms in the plane — the case of a circle and points
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Periodical
- Title:
- Advances in geometry
- Publication:
-
Berlin [u.a.]: de Gruyter, 2001 -
- Scope:
- Online-Ressource
- Note:
- Gesehen am 26.06.20
- ISSN:
- 1615-7168
- ZDB-ID:
- 2043066-8
- Keywords:
- Geometrie ; Zeitschrift
- Classification:
- Mathematik
- DDC Group:
- 500 Naturwissenschaften
- Copyright:
- Rights reserved
- Accessibility:
- Eingeschränkter Zugang mit Nutzungsbeschränkungen
- Collection:
- Mathematik
Article
- Title:
- Betweenness isomorphisms in the plane — the case of a circle and points
- Publication:
-
Berlin [u.a.]: de Gruyter, 2024
- Language:
- English
- Scope:
- Online-Ressource
- Note:
- Kein Open Access
- Archivierung/Langzeitarchivierung gewährleistet
- Keywords:
- Betweenness isomorphism classes ; circles with finitely many points inside ; group actions ; 52C45 ; 03E20 ; 51M04 ; 14L30
- Classification:
- Mathematik
- Sonstiges
- Collection:
- Mathematik
- Sonstiges
- Copyright:
- Rights reserved
- Accessibility:
- Eingeschränkter Zugang mit Nutzungsbeschränkungen
- Information:
-
Abstract: Two subsets A, B of the plane are betweenness isomorphic if there is a bijection f: A → B such that, for every x, y, z ∈ A, the point f (z) lies on the line segment connecting f (x) and f (y) if and only if z lies on the line segment connecting x and y. In general, it is quite difficult to tell whether two given subsets of the plane are betweenness isomorphic. We concentrate on the case when each of the sets A, B is of the form C ∪ D where C is a circle and D is a finite set. We fully characterize the betweenness isomorphism classes in the family of all circles with three collinear points inside. In particular, we show that there are only countably many isomorphism classes, for which we provide an algebraic description.