Orthonormal basis functions for L^2(R)

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Sets of functions can indeed form an orthonormal basis for the space of square integrable functions over the reals, L²(ℝ). Hermite polynomials serve as an orthogonal basis with a specific weight function, and they can be scaled to achieve orthonormality. The Haar wavelet is another example that provides an orthonormal basis, particularly on the unit interval. The discussion raises the question of additional orthonormal bases for functions in L²(ℝ) that have support across the entire real line, particularly those that are rapidly decaying. Exploring these bases can enhance understanding of function spaces in mathematical analysis.
mnb96
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Hello,

are there sets of functions that form an orthonormal basis for the space of square integrable functions over the reals L2(ℝ)?
According to Wikipedia the hermite polynomials form an orthogonal basis (w.r.t. to a certain weight function) for L2(ℝ). So I guess it would be a matter of multiplying the polynomials by suitable scalars in order to make them orthonormal.
Are there other known examples besides the Hermite polynomials?
 
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Hi micromass!
thanks for your reply. Your answer basically answer my question.
Apparently the Haar wavelets "constitute a complete orthogonal system for the functions on the unit interval".

I was now wondering if there are more orthonormal bases for functions in L2(ℝ) whose support is the whole real line, e.g. rapidly decaying functions.
 
I am studying the mathematical formalism behind non-commutative geometry approach to quantum gravity. I was reading about Hopf algebras and their Drinfeld twist with a specific example of the Moyal-Weyl twist defined as F=exp(-iλ/2θ^(μν)∂_μ⊗∂_ν) where λ is a constant parametar and θ antisymmetric constant tensor. {∂_μ} is the basis of the tangent vector space over the underlying spacetime Now, from my understanding the enveloping algebra which appears in the definition of the Hopf algebra...

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