Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: More about spontaneous Lorentz-violation and infrared modification of
  gravity   We consider a model with Lorentz-violating vector field condensates, in which
dispersion laws of all perturbations, including tensor modes, undergo
non-trivial modification in the infrared. The model is free of ghosts and
tachyons at high 3-momenta. At low 3-momenta there are ghosts, and at even
lower 3-momenta there exist tachyons. Still, with appropriate choice of
parameters, the model is phenomenologically acceptable. Beyond a certain large
distance scale and even larger time scale, the gravity of a static source
changes from that of General Relativity to that of van Dam--Veltman--Zakharov
limit of the Fierz--Pauli theory. Yet the late time cosmological evolution is
always determined by the standard Friedmann equation, modulo small correction
to the ``cosmological Planck mass'', so the modification of gravity cannot by
itself explain the accelerated expansion of the Universe. We argue that the
latter property is generic in a wide class of models with condensates.

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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: cond-mat
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The categories of this paper are: math
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The categories of this paper are: eess
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: gr-qc