Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Orthogonal almost complex structures on the Riemannian products of
  even-dimensional round spheres   We discuss the integrability of orthogonal almost complex structures on
Riemannian products of even-dimensional round spheres and give a partial answer
to the question raised by E. Calabi concerning the existence of complex
structures on a product manifold of a round 2-sphere and a round 4-sphere.

8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
3
The categories of this paper are: physics
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph