Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New results in the XXZ open spin chain   In this review, I describe a recent approach based on the representation
theory of the $q-$Onsager algebra which is used to derive exact results for the
XXZ open spin chain. The complete spectrum and eigenstates are obtained as
rational functions of a single variable which discrete values correspond to the
roots of a certain characteristic polynomial. Comments and open problems are
also presented.

30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph