Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Can gravity account for the emergence of classicality?   A recent debate has ensued over the claim by Pikovski et al. [Nat. Phys. 11,
668 (2015)] that systems with internal degrees of freedom undergo a universal,
gravity-induced, type of decoherence that explains their quantum-to-classical
transition. This decoherence is supposed to arise from the different
gravitational redshifts experienced by such systems when placed in a
superposition of two wave packets at different heights in a gravitational
field. Here we investigate some aspects of the discussion with the aid of
simple examples. In particular, we first resolve an apparent conflict between
the reported results and the equivalence principle by noting that the static
and free-fall descriptions focus on states associated with different
hypersurfaces. Next, we emphasize that predictions regarding the observability
of interference become relevant only in the context of concrete experimental
settings. As a result, we caution against hasty claims of universal validity.
Finally, we dispute the claim that, at least in the scenarios discussed by
Pikovski et al., gravitation is responsible for the reported results, and we
question the alleged ability of decoherence to explain the quantum-to-classical
transition. In consequence, we argue against the extraordinary assertion by
Pikovski et al. that gravity can account for the emergence of classicality.

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The categories of this paper are: cond-mat
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The categories of this paper are: hep-th
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The categories of this paper are: supr-con
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The categories of this paper are: cs
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The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: adap-org
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The categories of this paper are: math
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat