Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Navier-Stokes equations: an analysis of a possible gap to achieve the
  energy equality   The paper is concerned with the IBVP of the Navier-Stokes equations. The goal
is the attempt to construct a weak solution enjoying an energy equality. This
result is a natural continuation and improvement of the one obtained by the
same authors in [2].

3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex