Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: General reference frames and their associated space manifolds   We propose a formal definition of a general reference frame in a general
spacetime, as an equivalence class of charts. This formal definition
corresponds with the notion of a reference frame as being a (fictitious)
deformable body, but we assume, moreover, that the time coordinate is fixed.
This is necessary for quantum mechanics, because the Hamiltonian operator
depends on the choice of the time coordinate. Our definition allows us to
associate rigorously with each reference frame F, a unique "space" (a
three-dimensional differentiable manifold), which is the set of the world lines
bound to F. This also is very useful for quantum mechanics. We briefly discuss
the application of these concepts to G\"odel's universe.

15
The categories of this paper are: nucl-ex
28
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: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: funct-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-bio
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The categories of this paper are: eess
4
The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin