Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the possibility of metastable metallic hydrogen   Metallic hydrogen is expected to exhibit remarkable physics. Examples include
high-temperature superconductivity and possible novel types of quantum fluids.
These could have revolutionary practical applications. The pressures required
to obtain metallic hydrogen, however, are expected to be significant. For
practical, and terrestrial applications, a key question is therefore whether
this phase is metastable at lower pressures. In this work, this possibility is
investigated, using first-principles simulations. The results show that
metallic hydrogen is metastable, but strongly suggest that it is not so to
ambient conditions. Implications of these results for fundamental physics, and
also practical applications of metastable metallic hydrogen are discussed.

15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph