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 [...]

## Recent comments

Yongzhi: I think that the domain of the function g in Fact 21 should ...El Manolo: I can't figure out ex.12 b) and c) in the proposed way. Tha...R.: Is $\rho\neq 0$ required in 1(f)?R.: Typo: they introduced also introduced “tribes”Chin Ho Lee: they introduced also introduced “tribes” -> they also int...Mathias Niepert: This is not a correction but a question concerning the stabi...Ravi Boppana: In the hint to Exercise 21, should $(-\frac{1}{2} + \frac{\s...