From Computational Certification to Exact Coordinates: Heilbronn's Triangle Problem on the Unit Square Using Mixed-Integer Optimization

This paper presents an optimized "optimize-then-refine" framework combining mixed-integer nonlinear programming with exact symbolic computation to solve Heilbronn's triangle problem for n=9n=9 with certified global optimality in minutes, thereby proving the optimality of a 2002 configuration and deriving exact coordinates for n=5n=5 through $9$.

Nathan Sudermann-MerxFri, 13 Ma🔢 math

A characterization of graphs with \a\coronaG+\a\coreG=2α(G)+1\a{\corona G}+\a{\core G}=2\alpha(G)+1

This paper provides a complete characterization of graphs satisfying the equation corona(G)+core(G)=2α(G)+1|\text{corona}(G)| + |\text{core}(G)| = 2\alpha(G) + 1, thereby solving an open problem posed by Levit and Mandrescu and extending known results from graphs with a unique odd cycle to a broader family containing arbitrarily many odd cycles.

Kevin PereyraFri, 13 Ma🔢 math

On the maximum number of tangencies among $1$-intersecting curves

This paper improves the known upper bounds on the maximum number of tangencies among nn 1-intersecting Jordan arcs from O(n7/4)O(n^{7/4}) to O(n5/3)O(n^{5/3}) for the general case and to O(n3/2)O(n^{3/2}) for the strictly 1-intersecting case, while also establishing tighter bounds for specific variants involving xx-monotone curves and proving a new graph-theoretic result.

Eyal Ackerman, Balázs KeszeghFri, 13 Ma🔢 math