Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Semi-fermionic approach for quantum spin systems   We present a general derivation of semi-fermionic representation for
generators of SU(N) group as a bilinear combination of Fermi operators. The
constraints are fulfilled by means of imaginary Lagrange multipliers. The
important case of SU(2) group is discussed. We demonstrate how the idea of
semi-fermionic representation might be extended to the groups possessing
dynamic symmetries. As an example, SO(4) group is considered. We illustrate the
application of semi-fermionic representations for various problems of strongly
correlated physics.

22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th