On left regular bands and real conic–line arrangements

Michael Friedman, David Garber

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


An arrangement of curves in the real plane divides it into a collection of faces. In the case of line arrangements, there exists an associative product which gives this collection a structure of a left regular band. A natural question is whether the same is possible for other arrangements. In this paper, we try to answer this question for the simplest generalization of line arrangements, that is, conic–line arrangements. Investigating the different algebraic structures induced by the face poset of a conic–line arrangement, we present two different generalizations for the product and its associated structures: an alternative left regular band and an associative aperiodic semigroup. We also study the structure of sub left regular bands induced by these arrangements. We finish with some chamber counting results for conic–line arrangements.

Original languageEnglish
Pages (from-to)83-139
Number of pages57
JournalSemigroup Forum
Issue number1
StatePublished - 15 Feb 2019
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2018, Springer Science+Business Media, LLC, part of Springer Nature.


  • Aperiodic semigroup
  • Chamber counting
  • Conic-line arrangement
  • Face semigroup
  • Left regular band
  • Restriction-deletion theorem


Dive into the research topics of 'On left regular bands and real conic–line arrangements'. Together they form a unique fingerprint.

Cite this