Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The n-th order Moment of the Nuclear Charge Density and Contribution
  from the Neutrons   The relativistic expression for the $n$-th order moment of the nuclear charge
density is presented. For the mean square radius(msr) of the nuclear charge
density, the non-relativistic expression, which is equivalent to the
relativistic one, is also derived consistently up to $1/M^2$ with use of the
Foldy-Wouthuysen transformation. The difference between the relativistic and
non-relativistic expressions for the msr of the point proton density is also
discussed. The $n(\ge 4)$-th order moment of the nuclear charge density depends
on the point neutron density. The 4-th order moment yields a useful information
on the msr of the point neutron density, and is expected to play an important
role in electron scattering off neutron-rich nuclei.

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The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: cond-mat
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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: solv-int
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The categories of this paper are: econ
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The categories of this paper are: comp-gas
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The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: supr-con