A New Proof of the Csima-Sawyer Theorem Concerning Ordinary Points in Arrangements

A new and simpler proof is provided of the 1993 Theorem of Csima and Sawyer which states that in an arrangement of n lines or pseudolines in the projective plane, not all passing through a common point, then as long as the arrangement is not the 7 line arrangement due to Kelly and Moser having just
3 ordinary points, the arrangement must have at least ordinary points.

By: Jonathan Lenchner

Published in: RC24181 in 2007


This Research Report is available. This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). I have read and understand this notice and am a member of the scientific community outside or inside of IBM seeking a single copy only.


Questions about this service can be mailed to reports@us.ibm.com .