339 research outputs found
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
Planck scale inflationary spectra from quantum gravity
We derive the semiclassical evolution of massless minimally coupled scalar
matter in the de Sitter space-time from the Born-Oppenheimer reduction of the
Wheeler-DeWitt equation. We show that the dynamics of trans-Planckian modes can
be cast in the form of an effective modified dispersion relation and that high
energy corrections in the power spectrum of the cosmic microwave background
radiation produced during inflation remain very small if the initial state is
the Bunch-Davies vacuum.Comment: 6 pages, no figures, final version to appear in PR
Trans-Planckian footprints in inflationary cosmology
We consider a minimum uncertainty vacuum choice at a fixed energy scale
Lambda as an effective description of trans-Planckian physics, and discuss its
implications for the linear perturbations of a massless scalar field in
power-law inflationary models. We find possible effects with a magnitude of
order H/\Lambda in the power spectrum, in analogy with previous results for
de-Sitter space-time.Comment: 4 pages, 1 figure, final version to appear in Physics Letters
The deactivation of an NH3-SCR Cu-SAPO catalyst upon exposure to non-oxidizing conditions
Abstract A Cu-SAPO catalyst for NH3-SCR applications showed a significant loss of deNOx performance after exposure to oxygen-free conditions. The present work aims at elucidating the causes of the observed progressive deactivation by comparing different experimental procedures for the SCR activity tests. The adoption of an experimental protocol, which avoids the exposure to a non-oxidizing environment, ensured a stable activity of the Cu-SAPO catalyst. Moreover, treatment of the deactivated catalyst with an oxidizing mixture at 550 °C for 5 h enabled to partially recover the deNOx activity
The Inflaton and Time in the Matter-Gravity System
The emergence of time in the matter-gravity system is addressed within the
context of the inflationary paradigm. A quantum minisuperspace-homogeneous
minimally coupled inflaton system is studied with suitable initial conditions
leading to inflation and the system is approximately solved in the limit for
large scale factor. Subsequently normal matter (either non homogeneous inflaton
modes or lighter matter) is introduced as a perturbation and it is seen that
its presence requires the coarse averaging of a gravitational wave function
(which oscillates at trans-Planckian frequencies) having suitable initial
conditions. Such a wave function, which is common for all types of normal
matter, is associated with a ``time density'' in the sense that its modulus is
related to the amount of time spent in a given interval (or the rate of flow of
time). One is then finally led to an effective evolution equation (Schroedinger
Schwinger-Tomonaga) for ``normal'' matter. An analogy with the emergence of a
temperature in statistical mechanics is also pointed out.Comment: 14 pages, late
Particle Production in Tachyon Condensation
We study particle production in the tachyon condensation process as described
by different effective actions for the tachyon. By making use of invariant
operators, we are able to obtain exact results for the density of produced
particles, which is shown to depend strongly on the specific action. In
particular, the rate of particle production remains finite only for one of the
actions considered, hence confirming results previously appeared in the
literature.Comment: LaTeX, 6 pages, 3 figure
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.
- …