Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Normal matrix compressions   The recently developed theory of higher--rank numerical ranges originated in
problems of error correction in quantum information theory but its mathematical
implications now include a quite satisfactory understanding of \emph{scalar}
compressions of complex matrices. Here our aim is to make some first steps in
the more general program of understanding \emph{normal} compressions. We
establish some general principles for the program and make a detailed study of
rank--two normal compressions.

18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci