Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A renormalized excitonic method in terms of block excitations.
  Application to spin lattices   Dividing the lattice into blocks with singlet ground state and knowing the
exact low energy spectrum of the blocks and of dimers (or trimers) of blocks,
it is possible to approach the lowest part of the lattice spectrum through an
excitonic type effective model. The potentialities of the method are
illustrated on the 1-D frustrated chain and the 1/5-depleted square and the
plaquette 2-D lattices. The method correctly locates the phase transitions
between gapped and non-gapped phases.

2
The categories of this paper are: math
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
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The categories of this paper are: gr-qc
16
The categories of this paper are: stat