# Geometric interpretation of perturbation theory in quantum field theory

I am studying GR right now, and one interesting thing I learned about vectors is that they are defined to have the same properties as derivatives.

With this in mind, can I make a differential geometric interpretation of ordinary perturbation theory used in quantum field theory in the following way:?

1. The set of all field configurations makes a (very complicated) manifold.
2. We do perturbation theory about a background field configuration corresponding to a point on this manifold.
3. The perturbations are like expanding functions out to first order -- can be viewed like tangent vectors

Am I on some track to enlightenment, or is this a dead-end train of thought?

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At the non-rigorous/intuitive level, OP's observations are spot on. To facilitate such thinking, physicists often use DeWitt's condensed notation, where a field $\phi^{\alpha}(x)$ is written as $\phi^{i}$, while pretending that $i=(\alpha,x)$ is an index of a local coordinate $\phi^{i}$ for some differential manifold.