/sci/ - Science & Math

Anyone here know how to translate the expression to an integral? I'm in particular not sure about the external photon vertices and how to put all the factors in order --- there are three vertices and in particular if, say, one electron vertex would also have radiative corrections, then clearly the order must matter.
What do the Feynman rules prescribe here?

I'm just learning some probability theory and stochastic differential equations.
Am I right in thinking that the Ito lemma relates the first order infinitesimal variation of a function of a noisy variable to a second order variation, hence building the brige to the relation to physics looking differential equations?
Specifically, looking at the Feynman-Kac formula,

http://en.wikipedia.org/wiki/Feynman%E2%80%93Kac_formula

am I interpreting it right that it works because it goes the way backwards: relating the second order differential equation in u with the first order variation of u(X) where X is a random variable with an associated expectation value, and the formula says that the formula just says that to solve the differential equation you need to integrate up the first order probabilistic variation?