Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A few remarks about operator theory, topology, and analysis on metric
  spaces   Some basic facts about Fredholm indices are briefly reviewed, often used in
connection with Toeplitz and pseudodifferential operators, and which may be
relevant for operators associated to fractals.

11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ