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Dark energy and modified gravities // Tomsk State Pedagogical University Bulletin. 2004. Issue 7 (44). P. 49-57

We review the several models of the dark energy, which may generate the accelerated expansion of the present universe. We also discuss the the Big Rip singularity, which may occur when the equation of the state parameter w is less than -1. We show that the quantum correction would be very important near the singularity.

Dark energy, inflation and dark mater from modified F(R) gravity // Tomsk State Pedagogical University Bulletin. 2011. Issue 8 (110). P. 7-19

We review modified F(R)-gravity as realistic candidate to describe the observable universe expansion history. We show that recent cosmic acceleration, radiation/matter-dominated epoch and inflation could be realized in the framework of F(R)-gravity in the unified way. For some viable classes of F(R)-gravity, the Newton law is respected and there is no so-called matter instability (the very heavy positive mass for additional scalar degree of freedom is generated). The reconstruction program in modified gravity is also reviewed and it is demonstrated that any time-evolution of the universe expansion could be realized in F(R)-gravity. These models remain to be realistic also in the presence of non-minimal gravitational coupling with usual matter. It is shown that same model which passes local tests and predicts the unification of inflation with cosmic acceleration also describes dark matter thanks to presence of additional scalar degree of freedom and chameleon mechanism.

Keywords: dark energy, cosmological singularity, cosmic acceleration

NEW MODEL OF MASSIVE SPIN TWO FIELD // Tomsk State Pedagogical University Bulletin. 2014. Issue 12 (153). P. 203-207

We propose a new ghost-free model describing massive spin two field1 . This model consists of a kinetic term and interaction terms without derivative. We report on the properties of this model, especially we consider what could happen when this model couples with gravity. Although the model does not generate any ghost on the Minkowski space-time, it is not so clear whether or not this property is preserved even on curved space-time. In fact, Buchbinder et al. have found that the ghost appears even in the Fierz-Pauli theory on curved space-time if we do not include non-minimal coupling terms. We report on the model with interactions on curved space-time and show that we can construct a model without ghost by including non-minimal coupling terms.

Keywords: massive spin two field, massive gravity