I am studying domain walls. In Vilenkin's book on topological defects (p. 382) a classical field $\phi(z)$ forms a domain wall, while the field $\chi(x,y,z,t)$ of a particle interacts (scatters) with it.
He (without explanation) gives a reflection probability $R$ for the scattering of $\chi$. How is that calculated? How can you calculate the probability that a particle is somewhere from the field of the particle? I am hoping for something like $P(x) = |\psi(x)|^2$ in quantum mechanics.
I am asking about classical field theory, not QFT. Thank you for the help!
