Linear Operators in Hilbert Space - A Dense Question

In summary, the conversation discusses the existence of a proper subset of linear operators on a Hilbert space that is dense in the space. It is suggested that the set T, defined by linear combinations of basis elements with rational coefficients, is a possible solution. However, this solution may not be valid if the definition of "basis" refers to the usual definition of a basis of a vector space. The problem is considered trivial in its current form.
  • #1
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Let H be a Hilbert space and let S be the set of linear operators on H. Is there a proper subset of S that is dense in S?
 
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  • #2
S is a vector space, so it must have a basis. Let T be a subset of S defined by linear combinations of basis elements with rational coefficients. T is a proper subset of S and is dense in S.
 
  • #3
The question assumes that H (and thus S) is not a zero space, of course.

A more trivial solution would be to consider S \ {0}.
 
  • #4
Not if his meaning of "basis" refers to the usual definition of the basis of a vector space. (That is, B is a basis of S iff every element of S is uniquely expressed as a finite linear combination of elements of B.) Of course, as stated, the problem is rather trivial.

Way to bring up an old thread ;)
 

1. What is a linear operator in Hilbert space?

A linear operator in Hilbert space is a mathematical function that maps one vector to another within the space. It is a fundamental concept in functional analysis and is essential in understanding the behavior of functions in infinite-dimensional spaces.

2. How do linear operators in Hilbert space differ from those in finite-dimensional spaces?

The main difference is that linear operators in Hilbert space can operate on an infinite number of dimensions, whereas those in finite-dimensional spaces are limited to a specific number of dimensions. Additionally, the properties and behavior of linear operators in Hilbert space are more complex and require specialized techniques to analyze.

3. What is a dense question in relation to linear operators in Hilbert space?

A dense question is a question that delves deep into the properties and behavior of linear operators in Hilbert space, often requiring a thorough understanding of advanced mathematical concepts. It may involve topics such as spectral theory, functional calculus, and operator algebras.

4. What are some applications of linear operators in Hilbert space?

Linear operators in Hilbert space have numerous applications in mathematics, physics, and engineering. They are used to model and analyze physical systems, such as quantum mechanics and signal processing. They are also essential in the development of numerical methods and optimization algorithms.

5. How do I study and understand linear operators in Hilbert space?

To study linear operators in Hilbert space, it is important to have a solid foundation in functional analysis, linear algebra, and complex analysis. It is also helpful to have a strong understanding of measure theory and topology. Additionally, studying specific applications and examples can aid in understanding the properties and behavior of linear operators in Hilbert space.

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