Since we have P ′ ( t ) = π D 2 ρ ′ ( t ) e − π ρ ( t ) D 2 {\displaystyle P'(t)=\pi D^{2}\rho '(t)e^{-\pi \rho (t)D^{2}}} , in the case where ρ ′ ( t ) = 0 {\displaystyle \rho '(t)=0} , we get P ′ ( t ) = 0 {\displaystyle P'(t)=0} . Hence the probability of interaction is not changing over time. Hence P ( t ) {\displaystyle P(t)} will be the constant function during that time.
