Constraining nonlocal gravity by S2 star orbits

• Published in: Physical review. D 2019-02, Vol.99 (4), Article 044053
• Main Authors: Dialektopoulos, K. F., Borka, D., Capozziello, S., Borka Jovanović, V., Jovanović, P.
• Format: Article
• Language: English
• Subjects: Celestial bodies; Dark energy; Distortion; Gravitation; Orbits; Phenomenology
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.99.044053

Nonlocal theories of gravity have recently drawn a lot of attention because they can suitably represent the behavior of gravitational interaction in the ultraviolet regime. Furthermore, at infrared scales, they give rise to notable cosmological effects which could be important to describe the dark energy behavior. In particular, exponential forms of the distortion function seem particularly useful for this purpose. Using Noether symmetries, it can be shown that the only nontrivial form of the distortion function is the exponential one, which is working not only for cosmological minisuperspaces, but also in a spherically symmetric spacetime. Taking this result into account, we study the weak-field approximation of this type of nonlocal gravity, and comparing with the orbits of the S2 star around the Galactic center (NTT/VLT data), we set constraints on the parameters of the theory. Nonlocal effects do not play a significant role on the orbits of S2 stars around Sgr A* but give richer phenomenology at cosmological scales than the ΛCDM model. Also, we show that the nonlocal gravity model gives better agreement between theory and astronomical observations than Keplerian orbits.