On the cardinality of intersection sets in inversive planes

Marcus Greferath, Cornelia Rößing

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)


Intersection sets and blocking sets play an important role in contemporary finite geometry. There are cryptographic applications depending on their construction and combinatorial properties. This paper contributes to this topic by answering the question: how many circles of an inversive plane will be blocked by a d-element set of points that has successively been constructed using a greedy type algorithm? We derive a lower bound for this number and thus obtain an upper bound for the cardinality of an intersection set of smallest size. Defining a coefficient called greedy index, we finally give an asymptotic analysis for the blocking capabilities of circles and subplanes of inversive planes.
Original languageEnglish
Pages (from-to)181-188
Number of pages8
JournalJournal of Combinatorial Theory Series A
Issue number1
Publication statusPublished - 2002
MoE publication typeA1 Journal article-refereed


  • inversive plane
  • finite geometry
  • blocking set
  • intersection set


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