41 research outputs found
Exact solutions of nonlocal nonlinear field equations in cosmology
The final publication is
available at www.springerlink.comWe consider a method for seeking exact solutions of the equation of a nonlocal scalar field in a nonflat metric. In the Friedmann-Robertson-Walker metric, the proposed method can be used in the case of an arbitrary potential except linear and quadratic potentials, and it allows obtaining solutions in quadratures depending on two arbitrary parameters. We find exact solutions for an arbitrary cubic potential, which consideration is motivated by string field theory, and also for exponential, logarithmic, and power potentials. We show that the k-essence field can be added to the model to obtain exact solutions satisfying all the Einstein equations.Peer reviewe
Anisotropic solutions for gravity model with a scalar field
We study anisotropic solutions for the pure gravity model with a scalar
field in the Bianchi I metric. The evolution equations have a singularity at
zero value of the Ricci scalar for anisotropic solutions, whereas these
equations are smooth for isotropic solutions. So, there is no anisotropic
solution with the Ricci scalar smoothly changing its sign during evolution. We
have found anisotropic solutions using the conformal transformation of the
metric and the Einstein frame. The general solution in the Einstein frame has
been found explicitly. The corresponding solution in the Jordan frame has been
constructed in quadratures.Comment: 13 pages, accepted for publication in Phys. Atom. Nucle
gravity inflationary model with term
The proposed inflationary model, which is a one-parametric generalization of
the Starobinsky model, includes the term, where
the parameter is the inflaton mass, defined in the same way as in the
Starobinsky model, and is a dimensionless constant. Using the conformal
transformation and the Einstein frame potential, we obtain the inflationary
parameters of the model proposed. The value of the tensor-to-scalar ratio
is bigger than in the Starobinsky model. The considered inflationary model
produces a good fit to current observation data.Comment: 11 pages, 2 figure
Construction of inflationary scenarios with the Gauss-Bonnet term and nonminimal coupling
Inflationary models with a scalar field nonminimally coupled both with the
Ricci scalar and with the Gauss-Bonnet term are studied. We propose the way of
generalization of inflationary scenarios with the Gauss-Bonnet term and a
scalar field minimally coupled with the Ricci scalar to the corresponding
scenarios with a scalar field nonminimally coupled with the Ricci scalar. Using
the effective potential, we construct a set of models with the same values of
the scalar spectral index and the amplitude of the scalar perturbations
and different values of the tensor-to-scalar ratio .Comment: 11 pages, 5 figures, v2: minor corrections, references are added, to
appear in EPJ