Programme

O.17 -- Oral, NCTP-43

Date: Wednesday, 1 August 2018

Time: 11:30 - 11:50

$f(R)$-theory of gravity: perturbative solutions, motions and gravitational waves in a central field

Nguyen Anh Ky (1), Pham Van Ky (2), Nguyen Thi Hong Van (1,3)

(1) Institute of physics, Vietnam academy of science and technology, 10 Dao Tan, Ba Dinh, Hanoi, Viet Nam. (2) Graduate university of science and technology, Vietnam academy of science and technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Viet Nam. (3) Institute for interdisciplinary research in science and education, ICISE, Quy Nhon, Viet Nam.

Einstein's General theory of Relativity (GR) has been verified as an excellent theory of gravitation and, thus, it is a foundation of modern cosmological models. The GR is governed by the Einstein equation obtained from the Lagrangian $ {\cal L}_G= R $. This equation can describe very well gravitational phenomena of the normal matter, however, it ineffectively explains other observations such as the accelerated expansion of the Uinverse (i.e., the problem of dark energy or cosmological constant), dark matter, cosmic inflation, quantum gravity, etc. These new observations require an extension or modification of the GR. One of the most popular extensions of the GR is the so called $f(R)$-theory of gravity, or just $f(R)$-gravity. This theory is based on the Lagrangian ${\cal L}_G= f(R)$, where $ f(R) $ is a scalar function of the scalar curvature $ R $. This Lagragian leads to an equation replacing the Einstein equation. To find an exact soluion of this generalized equation is a hard, even impossible, tast. It is why an approximate method of solving the equation is often chosen.\\ Here, after making a brief review on the $f(R)$-theory of graviy, we use a pertubative method to solve the $f(R)$-generalized Einstein equation in a central field which, being a good approximation in many cases, is either static or non-static. As a test of an $f(R)$-gravity, the obtained solutions are applied to investigating different astronomical and cosmological problems such as motions and gravitational waves in a central field. New phenomena are predicted. References: Nguyen Anh Ky, Pham Van Ky and Nguyen Thi Hong Van, “Perturbative solutions of the f(R)-theory of gravity in a central gravitational field and some applications”, Eur. Phys. J. C 78 (2018) no.7, 539. https://doi.org/10.1140/epjc/s10052-018-6023-6 (open access).

Presenter: Pham Van Ky