Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Massive Klein--Gordon equation from a BEC-based analogue spacetime   We extend the "analogue spacetime" programme by investigating a
condensed-matter system that is in principle capable of simulating the massive
Klein--Gordon equation in curved spacetime. Since many elementary particles
have mass, this is an essential step in building realistic analogue models, and
a first step towards simulating quantum gravity phenomenology. Specifically, we
consider the class of two-component BECs subject to laser-induced transitions
between the components. This system exhibits a complicated spectrum of normal
mode excitations, which can be viewed as two interacting phonon modes that
exhibit the phenomenon of "refringence". We study the conditions required to
make these two phonon modes decouple. Once decoupled, the two distinct phonons
generically couple to distinct effective spacetimes, representing a bi-metric
model, with one of the modes acquiring a mass. In the eikonal limit the massive
mode exhibits the dispersion relation of a massive relativistic particle: omega
= sqrt[omega_0^2 + c^2 k^2], plus curved-space modifications. Furthermore, it
is possible to tune the system so that both modes can be arranged to travel at
the same speed, in which case the two phonon excitations couple to the same
effective metric. From the analogue spacetime perspective this situation
corresponds to the Einstein equivalence principle being satisfied.

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The categories of this paper are: q-bio
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The categories of this paper are: quant-ph
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The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas