Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gauge fixing by unitary transformations in QCD   The unitary gauge fixing technique is applied to the QCD hamiltonian
formulated in terms of angular variables. It is demonstrated that in this
formulation projections on the physical Hilbert space are unnecessary to
separate physical and unphysical degrees of freedom. Therefore the application
of the unitary gauge fixing technique can be extended to the operator level.

20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
19
The categories of this paper are: eess