Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mixed-Spin Ladders and Plaquette Spin Chains   We investigate low-energy properties of a generalized spin ladder model with
both of the spin alternation and the bond alternation, which allows us to
systematically study not only ladder systems but also alternating spin chains.
By exploiting non-linear $\sigma$ model techniques we study the model with
particular emphasis on the competition between gapful and gapless states. Our
approach turns out to provide a more consistent semi-classical description of
alternating spin chains than that in the previous work. We also study a closely
related model, i.e., a spin chain with plaquette structure, and show that
frustration causes little effect on its low-energy properties so far as the
strength of frustration is weaker than a certain critical value.

6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc