Equiangular lines in \(C^r\). II (Q1397700)

This paper continues the publication with the same title (as part I) in [ibid. 11, No. 2, 201--207 (2000; Zbl 0983.51010)]. Let \(r\) be a positive integer. The author investigates questions of finding integers \(n\) such that in the complex projective space \(\mathbb C\mathbb P^{r-1}\) there exists an \(F\)-regular \(n\)-tuple with invariant zero shape. In particular, following properties are shown for the largest integer \(n(r)\): \(n(r)\leq 2r -2\) for every odd integer \(r\) and \(n(1 +2^s)= 2^{s+1}\) for every integer \(s\). The geometric problem is related to the existence of some special matrices.