https://doi.org/10.1140/epjc/s10052-025-14312-9
Regular Article - Theoretical Physics
Friedmann–Lemaître universes and their metamorphoses
1
Clare Hall, University of Cambridge, Herschel Road, CB3 9AL, Cambridge, UK
2
Institute of Gravitation and Cosmology, RUDN University, ul. Miklukho-Maklaya 6, 117198, Moscow, Russia
Received:
28
November
2024
Accepted:
24
April
2025
Published online:
27
May
2025
We analyze the dynamics of the Friedmann–Lemaître universes taking into account the different roles played by the fluid parameter and the cosmological constant, as well as the degenerate character of the equations. We find that the Friedmann–Lemaître system reduces to four qualitatively inequivalent normal forms and write down the sets of all stable perturbations that may result (the ‘versal unfoldings’). These sets are of small codimension up to three. We then describe all possible parameter-dependent solutions and their transfigurations to other forms during evolution through the bifurcation sets, these are also fully described. This analysis leads to a picture of cosmological evolution determined by new parameters related to codimension which are zero in standard cosmology. The emerging versal solutions are all free of singularities, while other properties of them are also discussed.
© The Author(s) 2025
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