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Harmonic analysis is a generalisation of Fourier analysis that studies the properties of functions. Check out this tag for abstract harmonic analysis (on abelian locally compact groups), or Euclidean harmonic analysis (eg, Littlewood-Paley theory, singular integrals). It also covers harmonic analysis on tube domains, as well as the study of eigenvalues and eigenvectors of the Laplacian on domains, manifolds and graphs.

10 votes

Background for Hejhal's "The Selberg Trace Formula for $PSL(2, \mathbb{R})$

Deitmar and Echterhoff "Principles in Harmonic Analysis" Chapter 9 and 11 for the cocompact case (Hejhal I). It requires some familiarity with representation theory, but you seem to be more interested …
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7 votes
3 answers
1k views

A Question concerning the Fourier Transform of $\mathbb{R}$

Consider the classical Schwartz space $\mathcal{S}(\mathbb{R})$ together with the Fourier transform $\mathcal{F} : \mathcal{S}(\mathbb{R}) \rightarrow \mathcal{S}( \mathbb{R})$. Consider the subspace …
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7 votes
1 answer
1k views

Does random matrix theory make any prediction for the eigenvalue distributions of compact Ri...

Under RH, Montgomery has proven equidistribution results for the zeros of the Riemann Zeta function, which suggest a close connection of the distribution to certain results in Random matrix theory. An …
Marc Palm's user avatar
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3 votes
1 answer
280 views

Inducing from cocompact subgroups

Consider a locally compact group $G$ and a cocompact subgroup $H$, is it known that the induction of an irreducible representation $\pi$ of $H$ to $G$ decomposes discretely into a direct sum of irredu …
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3 votes
Accepted

When does a LCA group not contain a (closed) infinite cyclic subgroup?

In general, you have for a compactly generated group $G = \mathbb{R}^n \times \mathbb{Z}^n\times K$, with $K$ compact. And there is no way to embed $\mathbb{Z}$ discretely in something compact, see D …
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3 votes
1 answer
706 views

Ergodic decomposition of quasi-invariant measure

I have a reference request concerning Proposition 1.6 in the following article Link The setting: Let $G$ be a locally compact, second countable group. Let $S = (S, \mu)$ be a Polish space. Assume we h …
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3 votes

Topology on the Unitary Dual

Convergence in the Fell topology is equivalent to convergence of matrix coefficients. In the finite-dimensional case, this is equivalent as $\rho_n(g) v \rightarrow \rho(g)v$. Quote from Vogan (http: …
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3 votes
2 answers
709 views

Measures and structure on conjugacy classes

Given a locally compact group $G$, does there exist a measure $\nu$ on the conjugacy classes $conj(G)$ such that for $f \in C_c(G)$ $$ \int_G f(g) d \mu_G(g) = \int_{conj(H)} \int_{G / G_\gamma} f(g\g …
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2 votes

Where do the real analytic Eisenstein series live?

I can give an additional point of view, which is coming from the theory of parabolic induction. Parabolic induction plays a prominent role in representation theory and gives you a better intuition for …
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1 vote

Decomposition of $L^2(\Gamma \backslash G)$

The continuous part(=Eisenstein series) is understood by Moeglin-Waldspurgers book on Eisenstein series. The cuspidal part(=discrete part) is not well understood. Many things are still open. I am re …
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1 vote
Accepted

Spherical functions for sl(2,Q_p)

Be careful that among the irreducible unitary reps also the trivial representation has this property. That's why Paul Garrett says "embeds" into a prinicpal series, so you get not only unramified unit …
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1 vote

How does one show the existence of discrete and complementary series for SL(2,R)?

I found Traces of Hecke operators by Knightly and Li very readable. They treat Gl(2,R) by a similar method. Knapp or Wallach is also nice to read and more general. They have chapters for Sl(2,R) and …
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1 vote

The measure on the harmonic spectrum from Selberg trace formula

The physics paper regularizes the volume and I don't expect a straight forward translation between the Selberg trace formula setting for finite volume Riemann surface and the regularized upper halfpla …
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1 vote

Support of functions on compact groups, and their Fourier transforms

Certainly you can recover $f$ for a circle, because the group is abelian. In general, $f$ can be written as a linear combination of matrix coefficients, and for the Fourier transform of a general comp …
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1 vote

Orthonormal basis for $L^2(G/H)$.

This was merely too long for a comment. There is a certain preferable choice in a special situation, where one can choose an orthornormal basis of a rather specific nature. Let $H$ be cocompact in $ …
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