# Department of Theoretical Physics

National Institute of Physics and Nuclear Engineering - Horia Hulubei

Cosmology of Nonlocal Gravity

Branko Dragovich

Mathematical Institute, Serbian Academy of Sciences and Arts, Belgrade, Serbia

23.04.2018

General relativity is Einstein theory of gravity, which is successful at many scales, but still has not been verified for the universe as a whole. Hence there are many attempts to modify Einstein gravity with intention to describe accelerating expansion of the universe without dark energy and initial singularity. One of the recent and promising approaches is nonlocal modified gravity. Our nonlocal gravity is given by the action $S = \frac{1}{16 \pi G}\int \sqrt{-g} (R - 2\Lambda + P(R) \mathcal{F}(\Box) Q(R)) d^4x ,$ where $R$ is scalar curvature and $\Lambda$ -- cosmological constant. $P(R)$ and $Q(R)$ are some differentiable functions of $R$. $\mathcal{F}(\Box) = \sum_{n=1}^\infty f_n \Box^n$ is an analytic function of the d'Alambertian $\Box .$ We present some general properties of this nonlocal model as well as cosmological solutions for some concrete functions $P(R)$ and $Q(R) .$

#### NEWS

Busteni MESO 2017

SANDU International Conference on Quantum Physics, Crisan, May 2017

#### CERN - SEENET-MTP PhD Training Program in Bucharest, 8-14 November 2015

Brasov MESO 2014

Conference TEDxCERN@IFIN-HH  May 17th 2013

BW2013 Workshop - 10 years of the SEENET-MTP

Central European Workshop on Quantum Optics (CEWQO 2012)

International Summer School “Dynamics of open nuclear systems” 2012- Predeal

Constanta Meso 2011

CSSP10

Joint IFIN-HH,ICTP......

Department of Theoretical Physics
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