Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation angles, Fermi coordinates, and the Geodesic-Light-Cone gauge   We show that the angular directions locally measured by a static geodesic
observer in a generic cosmological background and expressed in the system of
Fermi Normal Coordinates always coincide with those expressed in the
Geodesic-Light-Cone (GLC) gauge, up to a local transformation which exploits
the residual gauge freedom of the GLC coordinates. This is not the case for
other gauges - like, for instance, the synchronous and longitudinal gauge -
commonly used in the context of observational cosmology. We also make an
explicit proposal for the GLC gauge-fixing condition that ensures a full
identification of its angles with the observational ones.

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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
0
The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics