Abstract
Abstract We discuss the effects of a (possibly) negative ( 1 + z ) 6 type contribution to the Friedmann equation in a spatially flat universe. No definite answer can be given as to the presence and magnitude of a particular mechanism, because any test using the general relation H ( z ) is able to estimate only the total of all sources of such a term. That is why we describe four possibilities: (1) geometric effects of loop quantum cosmology, (2) braneworld cosmology, (3) metric-affine gravity, and (4) cosmology with spinning fluid. We find the exact solutions for the models with ρ 2 correction in terms of elementary functions, and show all evolutional paths on their phase plane. Instead of the initial singularity, the generic feature is now a bounce.
Highlights
Cosmology, mainly due to its modern astronomical observations, seems to have been limited to what is nowadays dubbed the Cosmological Concordance Model (CCM)
In the observational cosmology this role is played by the cold dark matter model with the cosmological constant ( CDM model)
It offers the simplest explanation of the current Universe filled with two components— dark matter and dark energy [1,2]
Summary
Mainly due to its modern astronomical observations, seems to have been limited to what is nowadays dubbed the Cosmological Concordance Model (CCM). In the observational cosmology this role is played by the cold dark matter model with the cosmological constant ( CDM model) It offers the simplest explanation of the current Universe filled with two components— dark matter and dark energy [1,2]. What we consider here are the effects of theories which predict a ρ2-type modification to the Friedmann equation, which fits the above description Such reduction is a big simplification, we feel it is important to stress that such problems are explicitly solvable, which is often not checked before applying numerical studies in current works; and that it is possible to find and classify all types of evolutional scenarios which help to gain insight into more complicated models. We outline some recently significant possibilities of non-classical physics, and proceed to solve the resulting Friedmann equation in the subsequent sections
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