Absolute differences along Hamiltonian paths
  Given a set $A$ of real numbers consider the complete graph on the elements of $A$. We prove that if $A$ is an arithmetic progression then for every vertex $a\in A$ there exists an hamiltonian path such that the absolute differences of consecutive vertices are pairwise distinct. This result partially proves a conjecture by Zhi-Wei Sun. 
Francesco Monopoli
math.CO