Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The spin-1/2 anisotropic Heisenberg-chain in longitudinal and
  transversal magnetic fields: a DMRG study   Using the density matrix renormalization group technique, we evaluate the
low-energy spectrum (ground state and first excited states) of the anisotropic
antiferromagnetic spin-one-half chain under magnetic fields. We study both
homogeneous longitudinal and transversal fields as well as the influence of a
transversal staggered field on opening of a spin-gap. We find that only a
staggered transversal field opens a substantial gap.

16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys