THE COMPLEX PLANK PROBLEM
Keith Ball · Bulletin of the London Mathematical Society · 2001
It is shown that if (vj)n1 is a sequence of norm 1 vectors in a complex Hilbert space and (tj)n1 is a sequence of non-negative numbers satisfying [formula here] then there is a unit vector z for which [formula here] for every j. The result is a strong, complex analogue of the author's real plank theorem.