### Speaker

Prof.
Gohar Harutyunyan
(Yerevan State University)

### Description

Certain conceptual difficulties arising in the construction of the
cosmological evolution of the Universe (horizon and "flatness" problems), in
fact, do not affect the Standard Model tested by known observations. They
allow to determine reasonable initial conditions for classical Cosmology,
the inflationary process, which transforms the exponential expansion near
the Planck time to the power-law one.It is significant that while different
areas of space, being on the "distance" $H_{0}^{-1}$ ($H_{0}$ is the
corresponding Hubble parameter) stop to interact, the "memory" on the
previous connection remains that solves the horizon problem in the
inflationary model. The "flatness" problem is solved in the case where
during some time period the equation of state is given by $p=-\varepsilon $.
In this case, during $70$ Hubble times "flat" Universe is formed with
accuracy $10^{-60}$. Simultaneously the horizon problem is solved. This
exotic equation of state occurs naturally in all sustainable models. In
particular, the dynamics of a scalar field, under very natural assumptions,
leads to a satisfactory inflationary expansion. In this work, within the
framework of various conformal representations of the modified Jordan -
Brans - Dicke theory, inflationary solutions are constructed by taking into
account a specific scalar field for particular de Sitter models in which the
Universe is filled by the vacuum. We consider the inflationary expansion
from the Planck time till the beginning of the hot stage in the case of a
minimally coupled scalar field. In the first model we take a massless scalar
field and in the second one - a conformally coupled scalar field. In both
cases there is a specific cosmological scalar that is an analogous of the
variable cosmological constant.

### Primary author

Prof.
Gohar Harutyunyan
(Yerevan State University)

### Co-authors

Prof.
Ashot Hovsepyan
(Yerevan State University)
Prof.
Roland Avagyan
(Yerevan State University)