τ ∼ k (\frac{P}{M^{2}} )

|GP E| > KE

r_{strong} = \frac{2GM}{(Δv)^{2}}

f = n σ Δv

σ = π(r_{strong}^{2}) = π(\frac{2GM}{(Δv)^{2}} )^{2} ∝ M^{2}

Δv ∼ \frac{1}{2} (\frac{Δa}{a}) v ∝ (\frac{v}{a}) ∝ \frac{1}{P}

f ∝ n (M^{2}) (\frac{1}{P} ) ∝ \frac{M^{2}}{P}