Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exotic dense matter states pumped by relativistic laser plasma in the
  radiation dominant regime   The properties of high energy density plasma are under increasing scrutiny in
recent years due to their importance to our understanding of stellar interiors,
the cores of giant planets$^{1}$, and the properties of hot plasma in inertial
confinement fusion devices$^2$. When matter is heated by X-rays, electrons in
the inner shells are ionized before the valence electrons. Ionization from the
inside out creates atoms or ions with empty internal electron shells, which are
known as hollow atoms (or ions)$^{3,4,5}$. Recent advances in free-electron
laser (FEL) technology$^{6,7,8,9}$ have made possible the creation of condensed
matter consisting predominantly of hollow atoms. In this Letter, we demonstrate
that such exotic states of matter, which are very far from equilibrium, can
also be formed by more conventional optical laser technology when the laser
intensity approaches the radiation dominant regime$^{10}$. Such
photon-dominated systems are relevant to studies of photoionized plasmas found
in active galactic nuclei and X-ray binaries$^{11}$. Our results promote
laser-produced plasma as a unique ultra-bright x-ray source for future studies
of matter in extreme conditions as well as for radiography of biological
systems and for material science studies$^{12,13,14,15}$.

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The categories of this paper are: math-ph
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The categories of this paper are: adap-org
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The categories of this paper are: eess
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci