Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Causality and Cosmic Inflation   In the context of inflationary models with a pre-inflationary stage, in which
the Einstein equations are obeyed, the weak energy condition is satisfied, and
spacetime topology is trivial, we argue that homogeneity on super-Hubble scales
must be assumed as an initial condition. Models in which inflation arises from
field dynamics in a Friedman-Robertson-Walker background fall into this class
but models in which inflation originates at the Planck epoch, {\it eg.} chaotic
inflation, may evade this conclusion. Our arguments rest on causality and
general relativistic constraints on the structure of spacetime. We discuss
modifications to existing scenarios that may avoid the need for initial
large-scale homogeneity.

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The categories of this paper are: math-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: eess
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The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
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The categories of this paper are: funct-an
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom