# Homework Help: Number of weighted vacuum Feynman diagrams

1. Jun 5, 2012

### th13

I didn't know where to put this, because it isn't a homework or coursework I have to do but just a thing I'm trying to understand. Anyway, I have attached the problem as an image.

We have a scalar quartic lagrangian in d dimensions. It says that the number of vacuum Feynman diagrams, at a given order λ^k, weighted by their statistical factor, should depend on the number of dimension d.
If understand well what the "statistical factor" is, i.e. the number of ways to join the vertices of a given diagram, I can't figure out how it could be dependent on the number of space-time dimensions d. Any suggestions?

Thank you and sorry for my English

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