Abstract

We demonstrate an infinite family of pseudoline arrangements, in which an arrangement of $n$ pseudolines has no member incident to more than $4n/9$ points of intersection. This shows the "Strong Dirac" conjecture to be false for pseudolines.We also raise a number of open problems relating to possible differences between the structure of incidences between points and lines versus the structure of incidences between points and pseudolines.

Highlights

  • A central problem of discrete geometry is to elucidate the structure of incidences between points and lines

  • Until the recent explosion of applications of polynomial methods to problems in incidence geometry ([7, 16, 19]), the tools most successfully applied to questions about incidences between points and lines could be immediately applied to prove equivalent results for incidences between points and pseudolines

  • The main interest of the pseudoline arrangement presented here is that it shows that a natural conjecture that is widely believed to be true for straight lines is definitely false for pseudolines

Read more

Summary

A Pseudoline Counterexample to the Strong Dirac Conjecture

Submitted: Feb 14, 2012; Accepted: Apr 23, 2014; Published: May 13, 2014 Mathematics Subject Classification: 52C10

Introduction
Strong Dirac conjecture
Wedge presentation of symmetric pseudoline arrangements
Pseudoline counterexample to Strong Dirac conjecture
Open problems
Variations on the Strong Dirac
Dirac-Motzkin for Pseudolines

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.