349 research outputs found
K-Inflation in Noncommutative Space-Time
The power spectra of the scalar and tensor perturbations in the
noncommutative k-inflation model are calculated in this paper. In this model,
all the modes created when the stringy space-time uncertainty relation is
satisfied are generated inside the sound/Hubble horizon during inflation for
the scalar/tensor perturbations. It turns out that a linear term describing the
noncommutative space-time effect contributes to the power spectra of the scalar
and tensor perturbations. Confronting the general noncommutative k-inflation
model with latest results from \textit{Planck} and BICEP2, and taking and
as free parameters, we find that it is well consistent with
observations. However, for the two specific models, i.e. the tachyon and DBI
inflation models, it is found that the DBI model is not favored, while the
tachyon model lies inside the contour, if the e-folds number is
assumed to be around .Comment: 9 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:1404.016
Modified holographic dark energy in DGP brane world
In this paper, the cosmological dynamics of a modified holographic dark
energy which is derived from the UV/IR duality by considering the black hole
mass in higher dimensions as UV cutoff, is investigated in
Dvali-Gabadaze-Porrati (DGP) brane world model. We choose Hubble horizon and
future event horizon as IR cutoff respectively. And the two branches of the DGP
model are both taken into account. When Hubble horizon is considered as IR
cutoff, the modified holographic dark energy (HDE) behaves like an effect dark
energy that modification of gravity in pure DGP brane world model acts and it
can drive the expansion of the universe speed up at late time in
branch which in pure DGP model can not undergo an accelerating phase. When
future event horizon acts as IR cutoff, the equation of state parameter of the
modified HDE can cross the phantom divide.Comment: 8 pages, 4 figures, accepted for publication in PL
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