Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Perturbation Theory by Flow Equations: Dimerized and Frustrated S=1/2
  Chain   The flow equation method (Wegner 1994) is used as continuous unitary
transformation to construct perturbatively effective Hamiltonians. The method
is illustrated in detail for dimerized and frustrated antiferromagnetic S=1/2
chains. The effective Hamiltonians conserve the number of elementary
excitations which are S=1 magnons for the dimerized chains. The sectors of
different number of excitations are clearly separated. Easy-to-use results for
the gap, the dispersion and the ground state energies of the chains are
provided.

5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th