Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mathieu subspaces of codimension less than n of Mat_n(K)   We classify all Mathieu subspaces of ${\rm Mat}_n(K)$ of codimension less
than $n$, under the assumption that ${\rm char\,} K = 0$ or ${\rm char\,} K \ge
n$.
  More precisely, we show that any proper Mathieu subspace of ${\rm Mat}_n(K)$
of codimension less than $n$ is a subspace of $\{M \in {\rm Mat}_n(K) \mid {\rm
tr\,} M = 0\}$ if ${\rm char\,} K = 0$ or ${\rm char\,} K \ge n$. On the other
hand, we show that every subspace of $\{M \in {\rm Mat}_n(K) \mid {\rm tr\,} M
= 0\}$ of codimension less than $n$ in ${\rm Mat}_n(K)$ is a Mathieu subspace
of ${\rm Mat}_n(K)$ if ${\rm char\,} K = 0$ or ${\rm char\,} K \ge n+1$.

28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas