444 research outputs found
Phantom Mimicry on the Normal Branch of a DGP-inspired Braneworld Scenario with Curvature Effect
It has been shown recently that phantom-like effect can be realized on the
normal branch of the DGP setup without introduction of any phantom matter
neither in the bulk nor on the brane and therefore without violation of the
null energy condition. It has been shown also that inclusion of the
Gauss-Bonnet term in the bulk action modifies this picture via curvature
effects. Here, based on the Lue-Starkman conjecture on the dynamical screening
of the brane cosmological constant in the DGP setup, we extend this proposal to
a general DGP-inspired model that stringy effects in the
ultra-violet sector of the theory are taken into account by inclusion of the
Gauss-Bonnet term in the bulk action. We study cosmological dynamics of this
setup, especially its phantom-like behavior and possible crossing of the
phantom divide line especially with a non-minimally coupled quintessence field
on the brane. In this setup, scalar field and curvature quintessence are
treated in a unified framework.Comment: 25 Figures, To appear in MPL
Non-Minimal Inflation after WMAP3
The Wilkinson Microwave Anisotropy Probe (WMAP) three year results are used
to constraint non-minimal inflation models. Two different non-minimally coupled
scalar field potentials are considered to calculate corresponding slow-roll
parameters of non-minimal inflation. The results of numerical analysis of
parameter space are compared with WMAP3 data to find appropriate new
constraints on the values of the non-minimal coupling. A detailed comparison of
our results with previous studies reveals the present status of the non-minimal
inflation model after WMAP3.Comment: 16 pages, 11 figures, 2 tables, Revised Versio
Holographic Dark Energy from a Modified GBIG Scenario
We construct a holographic dark energy model in a braneworld setup that
gravity is induced on the brane embedded in a bulk with Gauss-Bonnet curvature
term. We include possible modification of the induced gravity and its coupling
with a canonical scalar field on the brane. Through a perturbational approach
to calculate the effective gravitation constant on the brane, we examine the
outcome of this model as a candidate for holographic dark energy.Comment: 13 pages, accepted for publication in IJMP
Braneworld Teleparallel Gravity
We study the gravity in the context of a braneworld teleparallel scenario.
The geometrical setup is assumed to be Randall-Sundrum II model where a single
positive tension brane is embedded in an infinite AdS bulk. We derive the
equivalent of Gauss-Codacci equations in teleparallel gravity and junction
conditions in this setup. Using these results we derive the induced
teleparallel field equations on the brane. We show that compared to general
relativity, the induced field equations in teleparallel gravity contain two
extra terms arising from the extra degrees of freedom in the teleparallel
Lagrangian. The term carrying the effects of the bulk to the brane is also
calculated and its implications are discussed.Comment: 7 pages, no figur
Braneworld setup and embedding in teleparallel gravity
We construct the setup of a five-dimensional braneworld scenario in
teleparallel gravity. Both cases of Minkowski and Friedmann-Robertson-Walker
branes embedded in Anti de Sitter bulk are studied and the effective 4-D action
were studied. 4-dimensional local Lorentz invariance is found to be recovered
in both cases. However, due to different junction conditions, the equations
governing the 4-D cosmological evolution differ from general relativistic case.
Using the results of Ref. [13], we consider a simple inflationary scenario in
this setup. The inflation parameters are found to be modified compared to
general relativistic case.Comment: 21 pages, no figure, Title Changed, Accepted for Publication in Phys.
Lett.
Noncommutative Inspired Reissner-Nordstr\"om Black Holes in Large Extra Dimensions
Recently, a new noncommutative geometry inspired solution of the coupled
Einstein-Maxwell field equations including black holes in 4-dimension is found.
In this paper, we generalize some aspects of this model to the
Reissner-Nordstr\"om (RN) like geometries with large extra dimensions. We
discuss Hawking radiation process based on noncommutative inspired solutions.
In this framework, existence of black hole remnant and possibility of its
detection in LHC are investigated.Comment: 24 pages, 12 figures, revised version to appear in Commun. Theor.
Phy
Bounds on quantum gravity parameter from the NJL effective model of QCD
Existence of a minimal measurable length, as an effective cutoff in the
ultraviolet regime, is a common feature of all approaches to the quantum
gravity proposal. It is widely believed that this length scale will be of the
order of the Planck length , where
is a dimensionless parameter that should be
fixed only by the experiments. This issue can be taken into account through the
deformed momentum spaces with compact topologies. In this paper, we consider
minimum length effects on the physical quantities related to three parameters
of the Nambu-Jona-Lasinio effective model of QCD by means of the
deformed measure which is defined on compact momentum space with topology. This measure is suggested by the doubly special relativity
theories, Snyder deformed spaces, and the deformed algebra that is obtained in
the light of the stability theory of Lie algebras. Using the current
experimental data of the particle physics collaboration, we constraint quantum
gravity parameter and we compare our results with bounds that are
arisen from the other experimental setups.Comment: 10 pages, no figure, accepted for publication in Europhysics Letter
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