Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Characterizations of Fredholm pairs and chains in Hilbert spaces   In this work characterizations of Fredholm pairs and chains of Hilbert space
operators are given. Following a well-known idea of several variable operator
theory in Hilbert spaces, the aforementioned objects are characterized in terms
of Fredholm linear and bounded maps. Furthermore, as an application of the main
results of this work, direct proofs of the stability properties of Fredholm
pairs and chains in Hilbert spaces are obtained.

24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat