[tw1010]

The notation R^G comes from invariant theory[1]. I'm not aware if it has any connection with exponentiation or if that is just notation, but it wouldn't surprise me because notation in algebra seems to have a tendency to be really sneaky and well connected.

[1] https://en.wikipedia.org/wiki/Invariant_theory

[yorwba]

Thank you for the link, now I know at least how to search for more information.

Can you confirm or refute my calculation of the growth of the number of parameters when the input variables are the sample points of an image and the polynomial has to be rotation-invaraint?