140 research outputs found
Resonance enhancement of dark matter interactions: the case for early kinetic decoupling and velocity dependent resonance width
Motivated by the possibility of enhancing dark matter (DM) self-interaction
cross-section , we have revisited the issue of DM
annihilation through a Breit-Wigner resonance. In this case thermally averaged
annihilation cross-section has strong temperature dependence, whereas elastic
scattering of DM on the thermal bath particles is suppressed. This leads to the
early kinetic decoupling of DM and an interesting interplay in the evolution of
DM density and temperature that can be described by a set of coupled Boltzmann
equations. The standard Breit-Wigner parametrization of a resonance propagator
is also corrected by including momentum dependence of the resonance width. It
has been shown that this effects may change predictions of DM relic density by
more than order of magnitude in some regions of the parameter space. Model
independent discussion is illustrated within a theory of Abelian vector dark
matter. The model assumes extra symmetry group factor and an additional
complex Higgs field needed to generate a mass for the dark vector boson, which
provides an extra neutral Higgs boson . We discuss the resonance
amplification of . It turns out that if DM abundance is
properly reproduced, the Fermi-LAT data favor heavy DM and constraint the
enhancement of to the range, which cannot provide a
solution to the small-scale structure problems.}Comment: 17 pages, 5 figures, v2: minor changes in text, BBN and CMB
constraints adde
Brane modeling in warped extra-dimension
Five-dimensional scenarios with infinitesimally thin branes replaced by
appropriate configurations of a scalar field were considered. A possibility of
periodic extra dimension was discussed in the presence on non-minimal
scalar-gravity coupling and a generalized Gibbons-Kallosh-Linde sum rule was
found. In order to avoid constraints imposed by periodicity, a non-compact
spacial extra dimension was introduced. A five dimensional model with warped
geometry and two thin branes mimicked by a scalar profile was constructed and
discussed. In the thin brane limit the model corresponds to a set-up with two
positive-tension branes. The presence of two branes allows to address the issue
of the hierarchy problem which could be solved by the standard warping of the
four dimensional metric provided the Higgs field is properly localized.
Stability of the background solution was discussed and verified in the presence
of the most general perturbations of the metric and the scalar field.Comment: 38+1 pages and 5 figures; v2: some references added and matches the
published version in JHE
Low-energy effective theory from a non-trivial scalar background in extra dimensions
Consequences of a non-trivial scalar field background for an effective 4D
theory were studied in the context of one compact extra dimension. The periodic
background that appears within the (1+4)-dimensional theory was found
and the excitations above the background (and their spectrum) were determined
analytically. It was shown that the presence of the non-trivial solution leads
to the existence of a minimal size of the extra dimension that is determined by
the mass parameter of the scalar potential. It was proved that imposing
orbifold antisymmetry boundary conditions allows us to eliminate a negative
mass squared Kaluza-Klein ground-state mode that otherwise would cause an
instability of the system. The localization of fermionic modes in the presence
of the non-trivial background was discussed in great detail varying the size of
the extra dimension and the strength of the Yukawa coupling. A simple exact
solution for the zero-mode fermionic states was found and the solution for
non-zero modes in terms of trigonometric series was constructed. The fermionic
mass spectrum, which reveals a very interesting structure, was found
numerically. It was shown that the natural size of the extra dimension is twice
as large as the period of the scalar background solution.Comment: 29 pages, 11 figures, 1 tabl
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