Abstract
For a graph whose vertex set is a finite set of points in the Euclidean d-space consider the closed (open) balls with diameters induced by its edges. The graph is called a (an open) Tverberg graph if these closed (open) balls intersect. Using the idea of halving lines, we showthat (i) for any finite set of points in the plane, there exists a Hamiltonian cycle that is a Tverberg graph; (ii) for any n red and n blue points in the plane, there exists a perfect red-blue matching that is a Tverberg graph. Also, we prove that (iii) for any even set of points in the Euclidean d-space, there exists a perfect matching that is an open Tverberg graph; (iv) for any n red and n blue points in the Euclidean d-space, there exists a perfect red-blue matching that is a Tverberg graph.