Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The transformation of irreducible tensor operators under spherical
  functions   The irreducible tensor operators and their tensor products employing Racah
algebra are studied. Transformation procedure of the coordinate system
operators act on are introduced. The rotation matrices and their
parametrization by the spherical coordinates of vector in the fixed and rotated
coordinate systems are determined. A new way of calculation of the irreducible
coupled tensor product matrix elements is suggested. As an example, the
proposed technique is applied for the matrix element construction for two
electrons in a field of a fixed nucleus.

24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas