Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fluctuations of the Energy Levels Number at the Mobility Edge   We present a detailed analysis of the behavior of two--level correlation
function $R(s)$ in the disordered sample. We show that in the vicinity of the
Anderson transition as well as in $2d$, the variance of the number of levels in
an energy band of a width $E$ has a linear behavior as a function of $E$. This
is related with an ``anomalous'' contribution to the sum rule for $R(s)$, which
comes from the ``ballistic'' region of $s$.

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The categories of this paper are: math-ph
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con
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The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: math
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
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The categories of this paper are: solv-int