Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universality of ac-conduction in anisotropic disordered systems: An
  effective medium approximation study   Anisotropic disordered system are studied in this work within the random
barrier model. In such systems the transition probabilities in different
directions have different probability density functions. The
frequency-dependent conductivity at low temperatures is obtained using an
effective medium approximation. It is shown that the isotropic universal
ac-conduction law, $\sigma \ln \sigma=u$, is recovered if properly scaled
conductivity ($\sigma$) and frequency ($u$) variables are used.

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The categories of this paper are: math
12
The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
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The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
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The categories of this paper are: eess
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph