An infinite hierarchy of exact equations is derived for the newly observed f0 avalanche in the Bak-Sneppen model. By solving the first-order exact equation, we find that the critical exponent γ, governing the divergence of the average avalanche size, is exactly 1 (for all dimensions), which has been confirmed by extensive simulations. Solution of the gap equation yields another universal result ρ=1 (ρ is the exponent of relaxation to attractor). Scaling relations are established among the crit...
