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This article is cited in 1 scientific paper (total in 1 paper)
Solving dynamical equations in general homogeneous isotropic cosmologies with a scalaron
A. T. Filippov Joint Institute for Nuclear Research, Dubna, Moscow Oblast,
Russia
Abstract:
We consider gauge-dependent dynamical equations describing homogeneous
isotropic cosmologies coupled to a scalar field $\psi$ (scalaron).
For flat cosmologies $(k=0)$, we analyze the gauge-independent equation
describing the differential $\chi(\alpha)\equiv\psi'(\alpha)$ of the map of
the metric $\alpha$ to the scalaron field $\psi$, which is the main
mathematical characteristic of a cosmology and locally defines its portrait
in the so-called $\alpha$ version. In the more customary $\psi$ version, the similar equation for the differential of the inverse map $\bar\chi(\psi)
\equiv\chi^{-1}(\alpha)$ is solved in an asymptotic approximation for
arbitrary potentials $v(\psi)$. In the flat case, $\bar\chi(\psi)$ and
$\chi^{-1}(\alpha)$ satisfy first-order differential equations depending
only on the logarithmic derivative of the potential, $v'(\psi)/v(\psi)$. If
an analytic solution for one of the $\chi$ functions is known, then we can
find all characteristics of the cosmological model. In the $\alpha$ version,
the full dynamical system is explicitly integrable for $k\ne0$ with any
potential $\bar v(\alpha)\equiv v[\psi(\alpha)]$ replacing $v(\psi)$. Until
one of the maps, which themselves depend on the potentials, is calculated,
no sort of analytic relation between these potentials can be found.
Nevertheless, such relations can be found in asymptotic regions or by
perturbation theory. If instead of a potential we specify a cosmological
portrait, then we can reconstruct the corresponding potential. The main
subject here is the mathematical structure of isotropic cosmologies. We also
briefly present basic applications to a more rigorous treatment of inflation
models in the framework of the $\alpha$ version of the isotropic scalaron
cosmology. In particular, we construct an inflationary perturbation
expansion for $\chi$. If the conditions for inflation to arise are
satisfied, i.e., if $v>0$, $k=0$, $\chi^2<6$, and $\chi(\alpha)$ satisfies a certain boundary condition as $\alpha\to-\infty$, then the expansion is
invariant under scaling the potential, and its first terms give the standard
inflationary parameters with higher-order corrections.
Keywords:
isotropic cosmology, scalar field, dynamical system, integrable model, gauge invariance, inflationary model.
Received: 09.09.2015 Revised: 21.10.2015
Citation:
A. T. Filippov, “Solving dynamical equations in general homogeneous isotropic cosmologies with a scalaron”, TMF, 188:1 (2016), 121–157; Theoret. and Math. Phys., 188:1 (2016), 1069–1098
Linking options:
https://www.mathnet.ru/eng/tmf9038https://doi.org/10.4213/tmf9038 https://www.mathnet.ru/eng/tmf/v188/i1/p121
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