I am trying to read Robert Zwanzig's paper `Diffusion in a rough potential' and am getting bogged down in notation. He says the mfpt is found by solving the differential equation
$e^{\beta U(x)}\partial/\partial x De^{-\beta U(x)}\partial/\partial x\langle t,x\rangle =-1$
Because he has written it all on one line I can't work out which bits are doing what. Is it supposed to be
$e^{\beta U(x)} \frac{\partial D}{\partial x} e^{-\beta U(x)}\frac{\partial \langle t,x\rangle}{\partial x}=-1$
is it a product of terms?
Based on Ian's helpful comment it may be
$e^{\beta U(x)} \frac{\partial \left(De^{-\beta U(x)}\frac{\partial \langle t,x\rangle}{\partial x}\right) }{\partial x} =-1$