A Parameter-Free Derivation of the Glueball Mass: Historical BSFT Approach

We review the application of boundary string field theory (BSFT) methods, circa 2001, to the QCD glueball spectrum. The BSFT beta=0 condition, with inputs n=2, χ=3800, t=10^4 and zero free parameters, yields M₀₊₊/m_ρ = 2.69. This result matches lattice QCD 2.58(14) at 0.7σ. We further note testable predictions for neutron star maximum mass M_max = 2.18 M_sun and CMB-S4 observable ΔN_eff = 0.334.