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Seminario / Gengo



Si comunica che il giorno 4 Aprile 2019, alle ore 14:45, in Sala Rappresentanza

il Dott. Massimo Gengo terrà un seminario dal titolo

"Cosmologies with matter and a scalar field"

In this talk I will discuss some multidimensional cosmological models à la Friedmann-Lemaître-Robertson-Walker (FLRW), in which the content of the universe consists of matter and of a scalar field (with possibly non zero space curvature eventually). The expression "matter" is used in a broad sense, and includes as a special case the radiation; the considered matter has pressure p and density ρ, related by an equation of state p = w ρ, with w an arbitrary constant (w = 0 in the case of dust; w = 1/d in the case of a radiation gas).
The scalar field Φ is minimally coupled to gravity, with a self-interaction potential V(Φ) and can be a Quintessence or a Phantom (depending on the sign of the kinetic part in its action functional); it is used as the mechanism that drives inflation, or as a model for the dark energy content of the universe (refining the standard cosmological constant model).
In the talk I will first discuss some integrable (i.e. explicitly solvable) cosmological models of the above kind, in which the field is a Quintessence; this analysis generalize previous results by Fré, Sagnotti and Sorin (Nuclear Physics B, 2013) who considered similar models with no matter content for the universe and zero spatial curvature.
In the last part of this talk I will discuss the problem of the particle horizon. I will prove that the occurrence of a particle horizon is unavoidable if the field is a Quintessence, the spatial curvature is non-positive and the usual energy conditions are fulfilled by matter.
On the contrary it is possible to build models with no horizon, based on a Phantom field and usual matter; examples will be given.


Per info: tiziano.penati@unimi.it/marco.sansottera@unimi.it

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22 marzo 2019
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