Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the semilattice of modal operators and decompositions of the
  discriminator   We investigate the join semilattice of modal operators on a Boolean algebra
$B$. Furthermore, we consider pairs $(f,g)$ of modal operators whose supremum
is the unary discriminator on $B$, and study the associated bi--modal algebras.

15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga