The fact that the Fourier characters $\chi_{\gamma} : {\mathbb F}_2^n \to \{-1,1\}$ form a group isomorphic to ${\mathbb F}_2^n$ is not a coincidence; the analogous result holds for any finite abelian group and is a special case of the theory of Pontryagin duality in harmonic analysis. We will see further examples of this in Chapter [...]

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Ryan O'Donnell: Yes, thanks! Sorry for the delay in replying.Ryan O'Donnell: No, it's definitely messed up. Will fix!Ryan O'Donnell: Thanks!Ryan O'Donnell: Hi Amir. It's just a 'dummy variable'; in some sense an X's...Ryan O'Donnell: Right, or I guess I can just switch 'codimension' to 'dimens...Ryan O'Donnell: Yep, thanks!Ryan O'Donnell: Thanks, seems like I spotted this one myself too. (Not corr...