“…In particular, there have emerged improvements to the lower bounds for N (18) [24,36] and improvements to the upper bounds for N (d) where d = 14, 16, 17, 18, 19, 20 [1, 2, 14, 15, 16]. There have also been various recent improvements to upper bounds for N (d) for d 24 using semidefinite programming, see [12,21,22,28,38].The asymptotic behaviour of N (d) is quadratic in d with a general upper bound of d(d+1)/2 [23, Theorem 3.5] and a general lower bound of (32d 2 + 328d + 29)/1089 [15, Corollary 2.8]. One can also consider the related problem of, for fixed α ∈ (0, 1), finding N α (d), the maximum number of lines in R d through the origin with pairwise angle arccos α.…”