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Sebastien Palcoux
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In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

enter image description here

Lemma 3.16. Let $G$ be a compact group and $Rep(G)$ the category of finite dimensional unitary representations of $G$. For $\pi \in Rep(G)$ $H_\pi$ denotes the representation space of $\pi$. Suppose we have a Hilbert subspace $K_\pi\subset H_\pi$ for each $\pi\in Rep(G)$ satisfying the following: $$K_\pi\oplus K_\sigma \subset K_{\pi \oplus \sigma}, \quad \pi,\sigma \in Rep(G),$$ $$K_\pi\otimes K_\sigma \subset K_{\pi \otimes \sigma}, \quad \pi,\sigma \in Rep(G),$$ $$\overline{K_\pi}=K_{\overline{\pi}}, \quad \pi \in Rep(G),$$ where $\overline{\pi}$ is the complex conjugate representation and $\overline{K_\pi}$ is the image of $K_\pi$ under the natural map from $H_\pi$ to its complex conjugate Hilbert space. Then there exists a closed subgroup $H \subset G$ such that $$K_\pi=\{\xi \in H_\pi; \pi(h)\xi=\xi,\quad h\in H\}.$$

By applying this result to finite groups, we get a Galois correspondence between subgroups and subsystems (of unitary representations).

Such a result seems "fundamental" in the finite group theory but I don't know an "old" reference for it.

Question: What's the first reference for this result in finite group theory?

In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

enter image description here

By applying this result to finite groups, we get a Galois correspondence between subgroups and subsystems (of unitary representations).

Such a result seems "fundamental" in the finite group theory but I don't know an "old" reference for it.

Question: What's the first reference for this result in finite group theory?

In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

Lemma 3.16. Let $G$ be a compact group and $Rep(G)$ the category of finite dimensional unitary representations of $G$. For $\pi \in Rep(G)$ $H_\pi$ denotes the representation space of $\pi$. Suppose we have a Hilbert subspace $K_\pi\subset H_\pi$ for each $\pi\in Rep(G)$ satisfying the following: $$K_\pi\oplus K_\sigma \subset K_{\pi \oplus \sigma}, \quad \pi,\sigma \in Rep(G),$$ $$K_\pi\otimes K_\sigma \subset K_{\pi \otimes \sigma}, \quad \pi,\sigma \in Rep(G),$$ $$\overline{K_\pi}=K_{\overline{\pi}}, \quad \pi \in Rep(G),$$ where $\overline{\pi}$ is the complex conjugate representation and $\overline{K_\pi}$ is the image of $K_\pi$ under the natural map from $H_\pi$ to its complex conjugate Hilbert space. Then there exists a closed subgroup $H \subset G$ such that $$K_\pi=\{\xi \in H_\pi; \pi(h)\xi=\xi,\quad h\in H\}.$$

By applying this result to finite groups, we get a Galois correspondence between subgroups and subsystems (of unitary representations).

Such a result seems "fundamental" in the finite group theory but I don't know an "old" reference for it.

Question: What's the first reference for this result in finite group theory?

minor edit
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Sebastien Palcoux
  • 27k
  • 5
  • 74
  • 186

In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

enter image description here

By applying this result to finite groups, we get a Galois correspondence between subgroups and subsystems (of unitary representations).

Such a result seems "fundamental" in the finite group theory but I didn'tdon't know an "old" reference for it.

Question: What's the first reference for this result in finite group theory?

In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

enter image description here

By applying this result to finite groups, we get a Galois correspondence between subgroups and subsystems (of unitary representations).

Such a result seems "fundamental" in the finite group theory but I didn't know an "old" reference for it.

Question: What's the first reference for this result in finite group theory?

In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

enter image description here

By applying this result to finite groups, we get a Galois correspondence between subgroups and subsystems (of unitary representations).

Such a result seems "fundamental" in the finite group theory but I don't know an "old" reference for it.

Question: What's the first reference for this result in finite group theory?

motivation
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Sebastien Palcoux
  • 27k
  • 5
  • 74
  • 186

In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

enter image description here

By applying this result to finite groups, we get a Galois correspondence between subgroups/subsystems and subsystems (of unitary representations).

Such a result seems "fundamental" in the finite group theory but I didn't know an "old" reference for it.

Question: What's the first reference for this result in finite group theory?

In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

enter image description here

By applying this result to finite groups, we get a Galois correspondence subgroups/subsystems.

Question: What's the first reference for this result in finite group theory?

In this paper (1998) by M. Izumi, R. Longo, S. Popa, there is the following result (page 49) on compact groups:

enter image description here

By applying this result to finite groups, we get a Galois correspondence between subgroups and subsystems (of unitary representations).

Such a result seems "fundamental" in the finite group theory but I didn't know an "old" reference for it.

Question: What's the first reference for this result in finite group theory?

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Sebastien Palcoux
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Sebastien Palcoux
  • 27k
  • 5
  • 74
  • 186
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Sebastien Palcoux
  • 27k
  • 5
  • 74
  • 186
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