On the number of digons in arrangements of pairwise intersecting circles

Eyal Ackerman, Gábor Damásdi, Balázs Keszegh +2

A long-standing open conjecture of Branko Grünbaum from 1972 states that any simple arrangement of $n$ pairwise intersecting pseudocircles in the plane can have at most $2n-2$ digo…