Petr V. Tretyakov

Dark energy from modified F(R ) -scalar -Gauss -Bonnet gravity

Abstract The modified F ( R ) -scalar-Gauss–Bonnet gravity is proposed as dark energy model. The reconstruction program for such theory is developed. It is explicitly demonstrated that the known classical universe expansion history (deceleration epoch, transition to acceleration and effective quintessence, phantom or cosmological constant era) may naturally occur in such unified theory for some (reconstructed) classes of scalar potentials. Gauss–Bonnet assisted dark energy is also proposed. The possibility of cosmic acceleration is studied there.

From Inflation to Dark Energy in the Non-Minimal Modified Gravity

We consider the modified gravity non-minimally coupled with matter Lagrangian for the description of early-time and late-time universe. Such

Reconstruction and deceleration–acceleration transitions in modified gravity

F(R)

Inflation in a conformally-invariant two-scalar-field theory with an extra

(

R^2

F(G)

term

) gravity in the absence of non-minimal coupling is viable theory which passes the local tests and reproduces the

A note on the viability of Gauss–Bonnet cosmology

\Lambda

Deceleration versus acceleration universe in different frames of F(R) gravity

CDM era. For qualitatively similar choice of non-minimal gravitational coupling function it is shown that the unified description of early-time inflation and late-time cosmic acceleration is possible. It is interesting that matter (scalar) which supports the inflationary era is gravitationally screened at late times. Hence, it may be effectively invisible at current universe.

Stability in higher-derivative matter fields theories

We discuss the cosmological reconstruction in modified Gauss–Bonnet and F(R) gravities. Two alternative representations of the action (with and without auxiliary scalar) are considered. The approximate description of deceleration–acceleration transition cosmologies is reconstructed. It is shown that cosmological solution containing Big Bang and Big Rip singularities may be reconstructed only using the representation with the auxiliary field. The analytical description of the deceleration–acceleration transition cosmology in modified Gauss–Bonnet gravity is demonstrated to be impossible at sufficiently general conditions.

Quantum effects, soft singularities and the fate of the universe in a braneworld cosmology

We explore inflationary cosmology in a theory where there are two scalar fields which non-minimally couple to the Ricci scalar and an additional