عنوان مجله
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European Physical Journal Plus
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چکیده
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Recently, a modified version of Rastall theory of gravity has been introduced in
which a varying coupling parameter could act as dark energy (DE) and thus, it can be held
responsible for the current accelerated expansion of the Universe. Motivated by this modification, we study here the evolution of linear and nonlinear perturbations in the matter content of
the Universe, utilizing spherically symmetric top-hat collapse scenario. The exact solutions
we obtain in linear regime show that as the Universe evolves, matter density perturbations
grow and reach a maximum value at a certain redshift after which these perturbations start
decreasing toward a finite positive value at the present time. Depending on model parameters, exact oscillatory solutions can be also found representing that matter perturbations
could experience either overdense and underdense regions during the dynamical evolution of
the Universe. Numerical solutions in nonlinear regime show that the amplitude of perturbations grows much faster than the linear one and diverges at a critical redshift. However, the
formation of collapsed structures is delayed as compared to CDM model. It is found that
the running mutual interaction between matter and geometry, encoded in the variable Rastall
coupling parameter, could drastically affect the dynamics of matter perturbations and their
growth rate during the evolution of the Universe
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