BBot
Apr 22'25
Exercise
[math]
\newcommand{\mathds}{\mathbb}[/math]
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Find an alternative, more conceptual proof for the equality
[[math]]
S_3^+=S_3
[[/math]]
by considering the following morphism, called universal coaction map,
[[math]]
\Phi:\mathbb C^3\to\mathbb C^3\otimes C(S_3^+)\quad,\quad
e_i\to\sum_je_j\otimes u_{ji}
[[/math]]
then by applying the Fourier transform over the group [math]\mathbb Z_3[/math] on the [math]\mathbb C^3[/math] part, and then observing that the coefficients of [math]u[/math], in Fourier transform, must clearly commute.