ὅδε οἶκος, ὦ ἑταῖρε, μνημεῖον ἐστιν ζῴων τῶν σοφῶν ἀνδρῶν, καὶ τῶν ἔργων αὐτῶν

PROGRAM

MATEMATIČKI INSTITUT SANU
Seminar geometriju, obrazovanje i vizualizaciju sa primenama

ČETVRTAK, 05.03.2020. u 17:15, Matematički institut SANU, sala 301f
COSMOLOGICAL SOLUTIONS OF A NEW NONLOCAL GRAVITY MODEL
In this talk, we present modification of GR extending $R - 2\Lambda$ by nonlocal term $\sqrt{R - 2\Lambda} \mathcal{F}(\Box)\sqrt{R - 2\Lambda}$, where $\mathcal{F}(\Box)$ is an analytic function of the d’Alembert operator $\Box$. The choice of $\mathcal{F}(\Box)$ in the analytic form is motivated by existence of analytic expressions with $\Box$ in string field theory and $p$-adic string theory.
We have found some exact cosmological solutions of the corresponding equations of motion without matter and with $\Lambda\neq 0$. One of these solutions is $a(t) = A t^{\frac 23} e^{\frac{\Lambda}{14}t^2}$, which contains properties similar to an interplay of the dark matter and the dark energy.
For this solution we computed some cosmological parameters which are in good agreement with their values in the standard $\Lambda$CDM model. This nonlocal gravity model has not the Minkowski space solution. Also, some constraints on function $\mathcal{F}(\Box)$ are obtained.

ČETVRTAK, 12.03.2020. u 17:15, Matematički institut SANU, sala 301f