20 research outputs found
Gauss-Bonnet Brane Cosmology with Radion Stabilization
We study cosmology in a five-dimensional brane-world with a stabilizing
effective potential for the radion and matter localized on the two branes. We
consider the corrections induced by the Gauss-Bonnet contribution to the total
action performing and expansion around the two possible static solutions up to
second order in the ratio between brane matter energy density and brane
tensions. The Friedmann and acceleration equations on the visible brane are
obtained and discussed.Comment: To be published in Phys.Rev.D, References Adde
Second order brane cosmology with radion stabilization
We study cosmology in the five-dimensional Randall-Sundrum brane-world with a
stabilizing effective potential for the radion and matter localized on the
branes. The analysis is performed by employing a perturbative expansion in the
ratio rho/V between the matter energy density on the branes and the brane
tensions around the static Randall-Sundrum solution (which has rho=0 and brane
tensions +-V). This approach ensures that the matter evolves adiabatically and
allows us to find approximate solutions to second order in \rho/V. Some
particular cases are then analyzed in details.Comment: 17 pages, RevTeX4, 4 figures, final version to appear in Phys. Rev.
Radion Induced Spontaneous Baryogenesis
We describe a possible scenario for the baryogenesis arising when matter is
added on the branes of a Randall-Sundrum model with a radion stabilizing
potential. We show that the radion field can naturally induce spontaneous
baryogenesis when the cosmological evolution for the matter on the branes is
taken into account.Comment: LaTeX 2e, 8 pages and no figures, minor corrections to match version
to appear in MPL
Quantum Gravity Effects in Black Holes at the LHC
We study possible back-reaction and quantum gravity effects in the
evaporation of black holes which could be produced at the LHC through a
modification of the Hawking emission. The corrections are phenomenologically
taken into account by employing a modified relation between the black hole mass
and temperature. The usual assumption that black holes explode around TeV
is also released, and the evaporation process is extended to (possibly much)
smaller final masses. We show that these effects could be observable for black
holes produced with a relatively large mass and should therefore be taken into
account when simulating micro-black hole events for the experiments planned at
the LHC.Comment: 14 pages, 8 figures, extended version of hep-ph/0601243 with new
analysis of final products, final version accepted for publication in J.
Phys.
Spacetime dynamics and baryogenesis in braneworld
We point out that the effective theory for the Randall-Sundrum braneworld
models with bulk fields contains the baryon number violation process depending
on the spacetime dynamics. Combining to the curvature-current interaction, the
net baryon number observed today may be explained. The resultant baryon to
entropy ratio is determined by the ratio of the Planck scales in four
dimensional and five dimensional spacetime except for the parameter for CP
violation.Comment: 8 pages, references adde
Black hole evaporation in a spherically symmetric non-commutative space-time
Recent work in the literature has studied the quantum-mechanical decay of a
Schwarzschild-like black hole, formed by gravitational collapse, into
almost-flat space-time and weak radiation at a very late time. The relevant
quantum amplitudes have been evaluated for bosonic and fermionic fields,
showing that no information is lost in collapse to a black hole. On the other
hand, recent developments in noncommutative geometry have shown that, in
general relativity, the effects of non-commutativity can be taken into account
by keeping the standard form of the Einstein tensor on the left-hand side of
the field equations and introducing a modified energy-momentum tensor as a
source on the right-hand side. Relying on the recently obtained
non-commutativity effect on a static, spherically symmetric metric, we have
considered from a new perspective the quantum amplitudes in black hole
evaporation. The general relativity analysis of spin-2 amplitudes has been
shown to be modified by a multiplicative factor F depending on a constant
non-commutativity parameter and on the upper limit R of the radial coordinate.
Limiting forms of F have been derived which are compatible with the adiabatic
approximation.Comment: 8 pages, Latex file with IOP macros, prepared for the QFEXT07
Conference, Leipzig, September 200
Gravitational amplitudes in black-hole evaporation: the effect of non-commutative geometry
Recent work in the literature has studied the quantum-mechanical decay of a
Schwarzschild-like black hole, formed by gravitational collapse, into
almost-flat space-time and weak radiation at a very late time. The relevant
quantum amplitudes have been evaluated for bosonic and fermionic fields,
showing that no information is lost in collapse to a black hole. On the other
hand, recent developments in noncommutative geometry have shown that, in
general relativity, the effects of noncommutativity can be taken into account
by keeping the standard form of the Einstein tensor on the left-hand side of
the field equations and introducing a modified energy-momentum tensor as a
source on the right-hand side. The present paper, relying on the recently
obtained noncommutativity effect on a static, spherically symmetric metric,
considers from a new perspective the quantum amplitudes in black hole
evaporation. The general relativity analysis of spin-2 amplitudes is shown to
be modified by a multiplicative factor F depending on a constant
non-commutativity parameter and on the upper limit R of the radial coordinate.
Limiting forms of F are derived which are compatible with the adiabatic
approximation here exploited. Approximate formulae for the particle emission
rate are also obtained within this framework.Comment: 14 pages, 2 figures, Latex macros. In the final version, section 5
has been amended, the presentation has been improved, and References 21-24
have been added. Last misprints amended in Section 5 and Ref. 2