Constructions of Spherical 3-Designs

Spherical t-designs are Chebyshev-type averaging sets on the d-sphere Sᵈ which are exact for polynomials of degree at most t. This concept was introduced in 1977 by Delsarte, Goethals, and Seidel, who also found the minimum possible size of such designs, in particular, that the number of points in a 3-design on Sᵈ must be at least n>=2d+2. In this paper we give explicit constructions for spherical 3-designs on Sᵈ consisting of n points for d=1 and n>=4; d=2 and n=6; 8; >= 10; d=3 and n=8; >=10; d = 4 and n = 10; 12; >= 14; d>=5 and n>=5 (d+1) /2 odd or n>=2d+2 even. We also provide some evidence that 3-designs of other sizes do not exist.