https://doi.org/10.1140/epjc/s10052-016-4426-9
Regular Article - Theoretical Physics
Do sewn up singularities falsify the Palatini cosmology?
1
Astronomical Observatory, Jagiellonian University, Orla 171, 30-244, Kraków, Poland
2
Mark Kac Complex Systems Research Centre, Jagiellonian University, ul. Łojasiewicza 11, 30-348, Kraków, Poland
3
Institute for Theoretical Physics, University of Wrocław, pl. M. Borna 9, 50-204, Wrocław, Poland
4
Dipartimento di Fisica, Universita di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cinthia, 9, 80126, Naples, Italy
* e-mail: marek.szydlowski@uj.edu.pl
Received:
30
April
2016
Accepted:
10
October
2016
Published online:
21
October
2016
We investigate further (cf. Borowiec et al. JCAP 1601(01):040, 2016) the Starobinsky cosmological model 
in the Palatini formalism with a Chaplygin gas and baryonic matter as a source in the context of singularities. The dynamics reduces to the 2D sewn dynamical system of a Newtonian type (a piece-wise-smooth dynamical system). We demonstrate that the presence of a sewn up freeze singularity (glued freeze type singularities) for the positive 
is, in this case, a generic feature of the early evolution of the universe. It is demonstrated that equal zero is a bifurcation parameter and the dynamics qualitatively changes as the sign is changing. On the other side for the case of negative instead of the big bang the sudden bounce singularity of a finite scale factor does appear and there is a generic class of bouncing solutions. While the 
is favored by data only very small values of 
parameter are allowed if we require agreement with the 
CDM model. From the statistical analysis of astronomical observations, we deduce that the case of only very small negative values of 
cannot be rejected. Therefore, observation data favor the universe without the ghost states (
) and tachyons (
).
© The Author(s), 2016
