Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Retrograde doping dependence of charge order in
  La$_{1.8-x}$Eu$_{0.2}$Sr$_x$CuO$_4$   Comparison with La$_{2-z-x}$Nd$_z$Sr$_x$CuO$_4$ ($z=0, 0.4$) shows that the
retrograde doping dependence of charge order in
La$_{1.8-x}$Eu$_{0.2}$Sr$_x$CuO$_4$ must be caused by a mechanism transcending
the common charge-order generation in the hole-doped lanthanum cuprates. This
could be a bond-stretching phonon with comparable momentum, $q \sim 0.24$
r.l.u., as observed in La$_{1.675}$Eu$_{0.2}$Sr$_{0.125}$CuO$_4$.

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The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: eess
35
The categories of this paper are: mtrl-th