Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravitational Friedel oscillations in higher-derivative and
  infinite-derivative gravity?   When a positively charged impurity is placed inside a cold metal, the
resulting charge density around that object exhibits characteristic ripples to
negative values, known as Friedel oscillations. In this essay, we describe a
somewhat analogous effect in (i) linearized higher-derivative gravity and (ii)
linearized infinite-derivative "ghost-free" gravity: when a gravitational
impurity (point particle) is placed in Minkowski vacuum, the local energy
density $\rho \equiv G{}_{\mu\nu}\xi{}^\mu \xi{}^\nu$ (with $\xi=\partial_t$)
exhibits oscillations to negative values. The wavelength of these oscillations
is roughly given by (i) the Pauli--Villars regularization scale and (ii) the
scale of non-locality. We hence dub this phenomenon gravitational Friedel
oscillations.

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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: astro-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: q-bio
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: cs