Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: FLRW spaces as submanifolds of $\mathbb{R}^6$: restriction to the
  Klein-Gordon operator   The FLRW spacetimes can be realized as submanifolds of $\mathbb{R}^6$. In
this paper we relate the Laplace-Beltrami operator for an homogeneous scalar
field $\phi$ of $\mathbb{R}^6$ to its explicit restriction on FLRW spacetimes.
We then make the link between the homogeneous solutions of the equation
$\square_6 \phi = 0$ in $\mathbb{R}^6$ and those of the Klein-Gordon equation
$(\square_{f} - \xi R^f + m^2)\phi^f=0 $ for the free field $\phi^f$ in the
FLRW spacetime. We obtain as a byproduct a formula for the Ricci scalar of the
FRLW spacetime in terms of the function $f$ defining this spacetime in
$\mathbb{R}^6$.

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The categories of this paper are: astro-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
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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: cs