How Do Continuous Linear Representations of S^1 Function in Hilbert Spaces?

In summary, a linear representation is a mathematical concept that uses linear transformations to describe the structure of a group or algebraic system. It is widely used in science, particularly in physics, to study the symmetries of physical systems. There are two main types of linear representations: faithful and projective. Compared to matrix representations, linear representations are more general and can involve a wider range of linear transformations. They are closely related to symmetry and are a useful tool for understanding symmetrical structures and phenomena.
  • #1
HMY
14
0
Let H be a separable Hilbert space. What are the continuous
linear representations of S^1 on H?

I read in an article this is defined as in the finite-dim case.
Why is this so?

Thanks.
 
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  • #2
Well S^1 is compact, so every continuous linear representation of S^1 on H is unitary (re-norm H if necessary) and decomposes into a direct sum of irreducible representations. And since S^1 is abelian, its irreducible representations are nothing other than its characters, i.e. they're one-dimensional.

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Related to How Do Continuous Linear Representations of S^1 Function in Hilbert Spaces?

1. What is a linear representation?

A linear representation is a mathematical concept that describes how a group or algebraic structure is represented by a set of linear transformations. It involves assigning a linear transformation to each element of the group or structure, preserving its algebraic operations.

2. How is a linear representation useful in science?

Linear representations are widely used in physics and other sciences to study the symmetries of physical systems. They provide a powerful tool for analyzing and understanding the behavior of complex systems, such as molecules, crystals, and quantum particles.

3. What are the different types of linear representations?

There are two main types of linear representations: faithful and projective. A faithful representation is one in which each element of the group or structure is uniquely represented by a linear transformation. A projective representation, on the other hand, is one in which elements may have multiple representations.

4. How is a linear representation different from a matrix representation?

A linear representation is a more general concept than a matrix representation. While a matrix representation assigns a matrix to each element of a group or structure, a linear representation can involve more general linear transformations, such as rotations, reflections, and translations.

5. How are linear representations related to symmetry?

Linear representations are closely related to symmetry because they describe how a group or structure can be transformed without changing its essential properties. In other words, linear representations capture the symmetries that exist in a system, making them a powerful tool for studying symmetrical structures and phenomena.

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