Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The 2p-2h electromagnetic response in the quasielastic peak and beyond   The contribution to the nuclear transverse response function R_T arising from
two particle-two hole (2p-2h) states excited through the action of
electromagnetic meson exchange currents (MEC) is computed in a fully
relativistic framework. The MEC considered are those carried by the pion and by
Delta degrees of freedom, the latter being viewed as a virtual nucleonic
resonance. The calculation is performed in the relativistic Fermi gas model in
which Lorentz covariance can be maintained. All 2p-2h many-body diagrams
containing two pionic lines that contribute to R_T are taken into account and
the relative impact of the various components of the MEC on R_T is addressed.
The non-relativistic limit of the MEC contributions is also discussed and
compared with the relativistic results to explore the role played by relativity
in obtaining the 2p-2h nuclear response.

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The categories of this paper are: nlin
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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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: mtrl-th
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: stat