Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Integrability of a disordered Heisenberg spin-1/2 chain   We investigate how the transition from integrability to nonintegrability
occurs by changing the parameters of the Hamiltonian of a Heisenberg spin-1/2
chain with defects. Randomly distributed defects may lead to quantum chaos. A
similar behavior is obtained in the presence of a single defect out of the
edges of the chain, suggesting that randomness is not the cause of chaos in
these systems, but the mere presence of a defect.

12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph