31 research outputs found
Induced Gravity on RS Branes
It is shown that a localized four-dimensional Einstein term, induced by
quantum corrections, modifies significantly the law of gravity in a
Randall-Sundrum brane world. In particular, the short-distance behavior of
gravity changes from five- to four-dimensional, while, depending on the values
of parameters, there can be an intermediate range where gravity behaves as in
five dimensions. The spectrum of graviton fluctuations around the brane, their
relative importance for the gravitational force, and the relevance of their
emission in the bulk for the brane cosmology are analysed. Finally, constraints
on parameters are derived from energy loss in astrophysical and particle
physics processes.Comment: 20 pages, 1 figure, JHEP.cl
QCD uncertainties at the LHC and the implications of HERA
Strong interaction physics will be ubiquitous at the Large Hadron Collider
since the colliding beams consist of confined quarks and gluons. Although the
main purpose of the LHC is to study the mechanism of electroweak symmetry
breaking and to search for physics beyond the Standard Model, to maximise the
precision and sensitivity of such anaylses it is necessary to understand in
detail various perturbative, semi-perturbative and non-perturbative QCD
effects. Many of these effects have been extensively studied at HERA and will
be studied further at HERA II. We discuss the impact of the knowledge thus
gained on physics at the LHC.Comment: Contributed to the Proceedings of DIS04, Strbske Pleso, Slovaki
Non-uniform Braneworld Stars: an Exact Solution
The first exact interior solution to Einstein's field equations for a static
and non-uniform braneworld star with local and non-local bulk terms is
presented. It is shown that the bulk Weyl scalar is always
negative inside the stellar distribution, in consequence it reduces both the
effective density and the effective pressure. It is found that the anisotropy
generated by bulk gravity effect has an acceptable physical behaviour inside
the distribution. Using a Reissner-N\"{o}rdstrom-like exterior solution, the
effects of bulk gravity on pressure and density are found through matching
conditions.Comment: 22 pages, 3 figures, version to be published in International Journal
of Modern Physics D (IJMPD
Gravitational collapse in braneworld models with curvature corrections
We study the collapse of a homogeneous braneworld dust cloud in the context
of the various curvature correction scenarios, namely, the induced-gravity, the
Gauss-Bonnet, and the combined induced-gravity and Gauss-Bonnet. In accordance
to the Randall-Sundrum model, and contrary to four-dimensional general
relativity, we show in all cases that the exterior spacetime on the brane is
non-static.Comment: References adde
Gravity induced over a smooth soliton
I consider gravity induced over a smooth (finite thickness) soliton. Graviton
kinetic term is coupled to bulk scalar that develops solitonic vacuum
expectation value. Couplings of Kaluza-Klein modes to soliton-localized matter
are suppressed, giving rise to crossover distance between
4D and 5D behavior. This system can be viewed as a finite thickness brane
regularization of the model of Dvali, Gabadadze and Porrati.Comment: 12 pages, 2 figure
Gravitino dark matter in brane-world cosmology
The gravitino dark matter hypothesis in the brane cosmology is studied. The
theoretical framework is the CMSSM for particle physics and RS II brane model
for gravity. It is found that the gravitino can play the role of dark matter in
the universe and we determine what the gravitino mass should be for different
values of the five-dimensional Planck mass. An upper bound is obtained for the
latter.Comment: Improved version with minor corrections, to appear in JCA
Gravitational waves from brane-world inflation with induced gravity
We calculate the amplitude of gravitational waves produced by inflation on a
de Sitter brane embedded in five-dimensional anti-de Sitter bulk spacetime,
extending previous calculations in Randall-Sundrum type cosmology to include
the effect of induced gravity corrections on the brane. These corrections arise
via a term in the brane action that is proportional to the brane Ricci scalar.
We find that, as in the Randall-Sundrum case, there is a mass gap between the
discrete zero-mode and a continuum of massive bulk modes, which are too heavy
to be excited during inflation. We give the normalization of the zero-mode as a
function of the Hubble rate on the brane and are thus able to calculate the
high energy correction to the spectrum of gravitational wave (tensor) modes
excited on large scales during inflation from initial vacuum fluctuations on
small scales. We also calculate the amplitude of density (scalar) perturbations
expected due to inflaton fluctuations on the brane, and show that the usual
four-dimensional consistency relation for the tensor/scalar ratio remains valid
for brane inflation with induced gravity corrections.Comment: 8 pages, 2 figure
Towards a covariant model for cosmic self-acceleration
An explicitly covariant formulation is presented of a modified DGP scenario
proposed recently [1], to avoid the instability of the self-accelerating
branch. It is based on the introduction of a bulk scalar field with appropriate
non-minimal coupling to the bulk Einstein-Hilbert term. The method is general
and may be applied to other models as well.Comment: 10 pages, no figures; v2: version published in JHE
Brane-bulk energy exchange : a model with the present universe as a global attractor
The role of brane-bulk energy exchange and of an induced gravity term on a
single braneworld of negative tension and vanishing effective cosmological
constant is studied. It is shown that for the physically interesting cases of
dust and radiation a unique global attractor which can realize our present
universe (accelerating and 0<Omega_{m0}<1) exists for a wide range of the
parameters of the model. For Omega_{m0}=0.3, independently of the other
parameters, the model predicts that the equation of state for the dark energy
today is w_{DE,0}=-1.4, while Omega_{m0}=0.03 leads to w_{DE,0}=-1.03. In
addition, during its evolution, w_{DE} crosses the w_{DE}=-1 line to smaller
values.Comment: 8 pages, 2 figures, RevTex; references added, to appear in JHE
Dark matter in supersymmetric models with axino LSP in Randall-Sundrum II brane model
The axino dark matter hypothesis in RSII brane model is studied. Within the
framework of CMSSM we assume that the lightest neutralino or stau is the NLSP,
and that the axino production has a single contribution from the NLSP decay. It
is found that the axino can play the role of dark matter in the universe and we
determine what the axino mass should be for different values of the
five-dimensional Planck mass. An upper bound is obtained for the latterComment: 12 pages,3 figures, accepted in JHE