  We study the lowest energy E of a semirelativistic system of N identical
massless bosons with Hamiltonian H= sum{i=1 to N} sqrt(p_i^2)+ sum{j>i=1 to N}
g |r_i - r_j|^2, g > 0. We prove the inequalities A [g N^2 (N-1)^2]^{1/3} < E <
B [g N^2 (N-1)^2]^{1/3}, where A = 2.33810741 and B = [81/(2 pi)]^{1/3} =
2.3447779. The average of these bounds determines E with an error less than
0.15% for all N > 1.
