Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Blue Spectra of Kalb-Ramond Axions and Fully Anisotropic String
  Cosmologies   The inhomogeneities associated with massless Kalb-Ramond axions can be
amplified not only in isotropic (four-dimensional) string cosmological models
but also in the fully anisotropic case. If the background geometry is
isotropic, the axions (which are not part of the homogeneous background)
develop, outside the horizon, growing modes leading, ultimately, to logarithmic
energy spectra which are "red" in frequency and increase at large distance
scales. We show that this conclusion can be evaded not only in the case of
higher dimensional backgrounds with contracting internal dimensions but also in
the case of string cosmological scenarios which are completely anisotropic in
four dimensions. In this case the logarithmic energy spectra turn out to be
"blue" in frequency and, consequently, decreasing at large distance scales. We
elaborate on anisotropic dilaton-driven models and we argue that, incidentally,
the background models leading to (or flat) logarithmic energy spectra for
axionic fluctuations are likely to be isotropized by the effect of string
tension corrections.

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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex