Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Evolution of Cosmological Type Ia Supernovae and the
  Gravitational Constant   There are at least three ways in which a varying gravitational constant $G$
could affect the interpretation of the recent high-redhisft Type Ia supernovae
results. If the local value of $G$ at the space-time location of distant
supernovae is different, it would change both the thermonuclear energy release
and the time scale of the supernova outburst. In both cases the effect is
related to a change in the Chandrasekhar mass $M_{\rm Ch}\propto G^{-3/2}$.
Moreover the integrated variation of $G$ with time would also affect cosmic
evolution and therefore the luminosity distance relation. Here we investigate
in a consistent way how these different effects of a varying $G$ could change
the current interpretation of the Hubble diagram of Type Ia supernovae. We
parametrize the variation of $G$ using scalar-tensor theories of gravity, such
as the Jordan-Brans-Dicke theory or its extensions. It is remarkable that
Dirac's hypothesis that $G$ should decrease with time can qualitatively explain
the observed $\Delta m \simeq 0.2$ mag decrease at $z\simeq 0.5$ (with respect
to a decelerating universe) and, at the same time, reduce the duration of the
risetimes of distant Type Ia supernovae as recently reported.

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The categories of this paper are: math
35
The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: stat
28
The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
37
The categories of this paper are: supr-con