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EARLY-TIME COSMIC DYNAMICS IN F(R) AND F(|Ωˆ|) EXTENSIONS OF BORN-INFELD GRAVITY // Tomsk State Pedagogical University Bulletin. 2014. Issue 12 (153). P. 158-163

We consider two types of modifications of Born-Infeld gravity in the Palatini formulation and explore their dynamics in the early universe. One of these families considers f(R) corrections to the Born-Infeld Lagrangian, which can be seen as modifications of the dynamics produced by the quantum effects of matter, while the other consists on different powers of the elementary building block of the Born-Infeld Lagrangian, which we denote by |Ωˆ|. We find that the two types of nonsingular solutions that arise in the original Born-Infeld theory are also present in these extensions, being bouncing solutions a stable and robust branch. Singular solutions with a period of approximate de Sitter inflation are found even in universes dominated by radiation.

Keywords: Cosmology, nonsingular universes, modified gravity, Palatini formalism

ACCELERATION AND DECELERATION IN COSMOLOGY WITH SPINOR AND SCALAR FIELDS NON-MINIMALLY COUPLED TO F(R) GRAVITY // Tomsk State Pedagogical University Bulletin. 2014. Issue 12 (153). P. 208-212

The solution to the current extending Universe problem, and the description of all stages of evolution compels scientists to consider various cosmological models. We combine two different approaches to the description of dark energy: modified gravity theory and introduction of the additional fields. We investigate the accelerating and decelerating cosmological models with non-linear spinor fields and non-minimal interaction of gravity with a scalar field. Scalar - tensor models are rather simple and also allow us to clearly define the separate stages of evolution. We explained the role of scalar and spinor potentials for emergence of accelerating or decelerating cosmology.

Keywords: cosmological model, non-minimally interactions, scalar field, spinor field

On the 25th Anniversary of the Scientific Journal “Tomsk State Pedagogical University Bulletin” // Tomsk State Pedagogical University Bulletin. 2023. Issue 1 (225). P. 7-8