Looking for empty topological wormhole spacetimes in F ( R )-modified gravity

Wormhole throats in R m gravity

We consider wormhole geometries subject to a gravitational action consisting of non-linear powers of the Ricci scalar. Specifically, wormhole throats are studied in the case where Einstein gravity is supplemented with a Ricci-squared and inverse Ricci term. In this modified theory it is found that static wormhole throats respecting the weak energy condition can exist. The analysis is done local...

Cosmological Dynamics from Modified f(R) Gravity in Einstein Frame

In this paper, we investigate and analyze the cosmological dynamics of the universe, with an effect of modified f(R) gravity emerging at cosmological scale. We choose the Einstein frame as a physical frame. We consider phase portraits of the universe at the late time from modified f(R) gravity model. This result gives our universe an acceleration phase expansion without introducing existence of...

f(R) theories of gravity

Modified gravity theories have received increased attention lately due to combined motivation coming from high-energy physics, cosmology and astrophysics. Among numerous alternatives to Einstein’s theory of gravity, theories which include higher order curvature invariants, and specifically the particular class of f(R) theories, have a long history. In the last five years there has been a new st...

Wormhole geometries in modified teleparallel gravity and theenergy conditions

Curvature scalar instability in f(R) gravity

An instability in the presence of matter in theories of gravity which include a 1/R correction in the gravitational action has been found by Dolgov and Kawasaki. In the present paper this instability is discussed for f(R) gravity in general. We focus on the Palatini formalism of the theory and it is shown that no such instability occurs in this version of f(R) gravity. The reasons for the appea...