Геометрија, образовање и визуализација са применама, 5. март 2020.

Наредни састанак Семинара биће одржан у четвртак, 5. марта 2020. у сали 301ф Математичког института САНУ са почетком у 14:15.

Предавач: Иван Димитријевић, Математички факултет, Универзитет у Београду

Наслов предавања: COSMOLOGICAL SOLUTIONS OF A NEW NONLOCAL GRAVITY MODEL

Апстракт:
In this tаlk, we present modification of GR extending $R - 2\Lambda$ by nonlocal term $\sqrt{R - 2\Lambda} \mathcal{F}(\Bоx)\сqрт{Р - 2\Lambda}$, wхере $\mathcal{F}(\Bоx)$ 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


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