25 research outputs found
Cylindrical solutions in Mimetic gravity
This paper is devoted to investigate cylindrical solutions in mimetic
gravity. The explicit forms of the metric of this theory, namely mimetic-Kasner
(say) have been obtained. In this study we have noticed that the Kasner's
family of exact solutions needs to be reconsidered under this type of modified
gravity. A no-go theorem is proposed for the exact solutions in the presence of
a cosmological constant.Comment: 8 pages, Title changed,references added, final version accepted in
the" European Physical Journal C
Boson stars from a gauge condensate
The boson star filled with two interacting scalar fields is investigated. The
scalar fields can be considered as a gauge condensate formed by SU(3) gauge
field quantized in a non-perturbative manner. The corresponding solution is
regular everywhere, has a finite energy and can be considered as a quantum
SU(3) version of the Bartnik - McKinnon particle-like solution.Comment: errors are corrected, one reference is adde
General slow-roll Inflation in f(R) gravity under the Palatini approach
Producci贸n Cient铆ficaSlow-roll inflation is analyzed in the context of modified gravity within the Palatini formalism. As shown in the literature, inflation in this framework requires the presence of non-traceless matter; otherwise, it does not occur just as a consequence of the nonlinear gravitational terms of the action. Nevertheless, by including a single scalar field that plays the role of the inflaton, slow-roll inflation can be performed in these theories, where the equations lead to an effective potential that modifies the dynamics. We obtain the general slow-roll parameters and analyze a simple model to illustrate the differences introduced by the gravitational terms under the Palatini approach, and the modifications on the spectral index and the tensor to scalar ratio predicted by the model.Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08052034)