23,809 research outputs found
Updating constraints on phantom crossing gravity
We establish constraints on gravity by considering the possibility of
a scenario that supports a phantom crossing of the equation of state parameter
. After determining the viable parameter space of the model, while
checking the impact on the background dynamics, we perform an analysis to
obtain constraints on cosmological parameters and determine the viability of
this scenario. To this end, we use combined data sets from cosmic chronometers
(CC), baryonic acoustic oscillations (BAO), redshift space distortion (RSD) and
Type Ia supernovae (SN) measurements from the latest Pantheon set, in which
the impact on the absolute magnitude due to the change of the effective
gravitational constant is also considered. It is found that a state where a
phantom crossing of happens is favored by data, and the
model is competitive with the CDM one by statistical criteria, such as
AIC and BIC. Additionally, we find evidence of the Hubble tension being
alleviated within the model, at the same time that it does not worsen
the growth one, indicating a possibility of the present scenario as an option
to address the current cosmic tensions.Comment: 18 pages, 6 figures, 2 tables. Updated results and references;
published in JCA
Effects of a CPT-even and Lorentz-violating nonminimal coupling on the electron-positron scattering
We propose a new \emph{CPT}-even and Lorentz-violating nonminimal coupling
between fermions and Abelian gauge fields involving the CPT-even tensor
of the standard model extension. We thus
investigate its effects on the cross section of the electron-positron
scattering by analyzing the process .
Such a study was performed for the parity-odd and parity-even nonbirefringent
components of the Lorentz-violating tensor.
Finally, by using experimental data available in the literature, we have
imposed upper bounds as tight as on the magnitude of the
CPT-even and Lorentz-violating parameters while nonminimally coupled.Comment: LaTeX2e, 06 pages, 01 figure
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