124,356 research outputs found
Fisher matrix forecasts for astrophysical tests of the stability of the fine-structure constant
We use Fisher Matrix analysis techniques to forecast the cosmological impact
of astrophysical tests of the stability of the fine-structure constant to be
carried out by the forthcoming ESPRESSO spectrograph at the VLT (due for
commissioning in late 2017), as well by the planned high-resolution
spectrograph (currently in Phase A) for the European Extremely Large Telescope.
Assuming a fiducial model without variations, we show that ESPRESSO
can improve current bounds on the E\"{o}tv\"{o}s parameter---which quantifies
Weak Equivalence Principle violations---by up to two orders of magnitude,
leading to stronger bounds than those expected from the ongoing tests with the
MICROSCOPE satellite, while constraints from the E-ELT should be competitive
with those of the proposed STEP satellite. Should an variation be
detected, these measurements will further constrain cosmological parameters,
being particularly sensitive to the dynamics of dark energy.Comment: Phys. Lett. B (in press
Brane bounce-type configurations in a string-like scenario
Brane world six dimensional scenarios with string like metric has been
proposed to alleviate the problem of field localization. However, these models
have been suffering from some drawbacks related with energy conditions as well
as from difficulties to find analytical solutions. In this work, we propose a
model where a brane is made of a scalar field with bounce-type configurations
and embedded in a bulk with a string-like metric. This model produces a sound
AdS scenario where none of the important physical quantities is infinite. Among
these quantities are the components of the energy momentum tensor, which have
its positivity ensured by a suitable choice of the bounce configurations.
Another advantage of this model is that the warp factor can be obtained
analytically from the equations of motion for the scalar field, obtaining as a
result a thick brane configuration, in a six dimensional context. Moreover, the
study of the scalar field localization in these scenario is done.Comment: 15 pages, 5 figures. To appear in Physics Letters
Soft supersymmetry breaking in the nonlinear sigma model
In this work we discuss the dynamical generation of mass in a deformed supersymmetric nonlinear sigma model in a two-dimensional ()
space-time. We introduce the deformation by imposing a constraint that softly
breaks supersymmetry. Through the tadpole method, we compute the effective
potential at leading order in expansion showing that the model exhibit a
dynamical generation of mass to the matter fields. Supersymmetry is recovered
in the limit of the deformation parameter going to zero.Comment: 9 pages, 2 figures. Revised version. arXiv admin note: text overlap
with arXiv:1308.471
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