Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Finite-frequency optical absorption in 1D conductors and Mott-Hubbard
  insulators   The frequency-dependent conductivity is studied for the one-dimensional
Hubbard model, using a selection rule, the Bethe ansatz, and symmetries
associated with conservation laws. For densities where the system is metallic
the absorption spectrum has two contributions, a Drude peak at $\omega = 0$
separated by a pseudogap from a broad absorption band whose lower edge is
characterized by a non-classical critical exponent. Our findings shed new light
on the ``far infrared puzzle'' and other optical properties of metallic organic
chain compounds.

19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys