Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Topics in Hilbert Spaces, Spectral Theory, and Harmonic Analysis   General expository paper concerning topics in Hilbert spaces, spectral
theory, and harmonic analysis. The preliminary section includes basic Banach
algebra and Hilbert space theory with a digression on Riesz bases. The second
and third sections are focused on deriving the spectral theorem for Hilbert
spaces in finite and arbitrary dimension, respectively. The fourth and fifth
sections present applications of the general theory: first to finite abelian
groups, then to the space $L^2(S^1,\mu)$.

22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas