Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modified Friedmann Equation and Inflation in Warped Codimension-two
  Braneworld   We study the Friedmann equation for the warped codimension-two braneworld
background which most closely resembles the Randall-Sundrum model. Extra matter
on the (Planck) 4-brane, with equation of state p_\theta=(\alpha-1)\rho for the
azimuthal pressure, is required to satisfy the junction conditions. For 1 <
\alpha < 5, we show that there are two static solutions to the Einstein
equations for given values of the brane stress-energies. Close to the static
solutions, the relation between Hubble expansion rate H and brane tension
reproduces the standard 4D result for small H, but exhibits unusual deviations
when H is of order the AdS curvature scale. The two static branches for 1
<\alpha < 5 are shown to come together smoothly at a maximum value of H;
however the radion is shown to be unstable in the branch with higher H. This
remains true even with a mechanism for stabilization of the radion, i.e., the
Goldberger-Wise (GW) mechanism, since large enough H overcomes the force of
stabilization. Even in the unstabilized case, cosmological constraints on the
time and spatial variation of Newton's constant are typically satisfied; only
fifth force constraints require the stabilization. For \alpha > 5 the model is
intrinsically stable, without the need for a GW field, and in this case we show
that inflationary predictions can be modified by the nonstandard Friedmann
equation; in particular it is possible to get an upper limit on the spectral
index, large deviations from the consistency condition between the tensor
spectrum and ratio r, and large running of the spectral index even though the
slow roll parameters remain small.

15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio