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Apr 20'25
[math] \newcommand{\mathds}{\mathbb}[/math]

Work out the Tannakian duality for the closed subgroups

[[math]] G\subset O_N [[/math]]

first as a consequence of the general results that we have, regarding the closed subgroups

[[math]] G\subset U_N [[/math]]

and then independently, by pointing out the simplifications that appear in the real case.

Apr 20'25
[math] \newcommand{\mathds}{\mathbb}[/math]

Work out the Tannakian duality for the closed subgroups

[[math]] G\subset U_N [[/math]]

whose fundamental representation is self-adjoint, up to equivalence,

[[math]] u\sim\bar{u} [[/math]]

first as a consequence of the results that we have, and then independently.

Apr 20'25
[math] \newcommand{\mathds}{\mathbb}[/math]

Check the Brauer theorems for [math]O_N,U_N[/math], which are both of type

[[math]] Hom(u^{\otimes k},u^{\otimes l})=span\left(T_\pi\Big|\pi\in D(k,l)\right) [[/math]]

for small values of the global length parameter, [math]k+l\in\{1,2,3\}[/math].

Apr 20'25
[math] \newcommand{\mathds}{\mathbb}[/math]

Write down Brauer theorems for the bistochastic groups

[[math]] B_N\subset O_N\quad,\quad C_N\subset U_N [[/math]]

by identifying first the partition which produces them, as subgroups of [math]O_N,U_N[/math].

Apr 20'25
[math] \newcommand{\mathds}{\mathbb}[/math]

Look up the original version of Tannakian duality, stating that [math]G[/math] can be recovered from the knowledge of its full category of representations [math]\mathcal R_G[/math], viewed as subcategory of the category [math]\mathcal H[/math] of the finite dimensional Hilbert spaces, with each [math]\pi\in\mathcal R_G[/math] corresponding to its Hilbert space [math]H_\pi\in\mathcal H[/math], and write down a brief account of this.

Apr 20'25
[math] \newcommand{\mathds}{\mathbb}[/math]

Look up the Doplicher-Roberts and Deligne theorems, stating that the compact group [math]G[/math] can be in fact recovered from the sole knowledge of the category [math]\mathcal R_G[/math], with no need for the embedding into [math]\mathcal H[/math], and write down a brief account of this.

Apr 20'25
[math] \newcommand{\mathds}{\mathbb}[/math]

Given a closed subgroup [math]G\subset_uU_N[/math], understand and then briefly explain, in a short piece of writing, why the [math]*[/math]-algebras

[[math]] C(k,k)=End(u^{\otimes k}) [[/math]]

form a planar algebra in the sense of Jones, and then comment as well on the various formulations of Tannakian duality, in the planar algebra setting.