Modified gravity revealed along geodesic tracks

The study of the dynamics of a two-body system in modified gravity constitutes a more complex problem than in Newtonian gravity. Numerical methods are typically needed to solve the equations of geodesics. Despite the complexity of the problem, the study of a two-body system in $f(R)$ gravity leads to a new exciting perspective hinting the right strategy to adopt in order to probe modified gravity. Our results point out some differences between the {\em semiclassical} (Newtonian) approach, and the {\em relativistic} (geodesic) one thus suggesting that the latter represents the best strategy for future tests of modified theories of gravity. { Finally, we have also highlighted the capability of forthcoming observations to serve as smoking gun of modified gravity revealing a departure from GR or further reducing the parameter space of $f(R)$ gravity}. \keywords{$f(R)$ gravity \and binary system \and geodesics \and precessionComment: 7 Pages, 2 figures. Accepted for publication on The European Physics Journal

Analysis of the Yukawa gravitational potential in f(R)f(R) gravity I: semiclassical periastron advance

The {\it concordance} cosmological model has been successfully tested throughout the last decades. Despite its successes, the fundamental nature of dark matter and dark energy is still unknown. Modifications of the gravitational action have been proposed as an alternative to these dark components. The straightforward modification of gravity is to generalize the action to a function, $f(R)$, of the scalar curvature. Thus one is able to describe the emergence and the evolution of the Large Scale Structure without any additional (unknown) dark component. In the weak field limit of the $f(R)$-gravity, a modified Newtonian gravitational potential arises. This gravitational potential accounts for an extra force, generally called fifth force, that produces a precession of the orbital motion even in the classic mechanical approach. We have shown that the orbits in the modified potential can be written as Keplerian orbits under some conditions on the strength and scale length of this extra force. Nevertheless, we have also shown that this extra term gives rise to the precession of the orbit. Thus, comparing our prediction with the measurements of the precession of some planetary motions, we have found that the strength of the fifth force must be in the range $[2.70-6.70]\times10^{-9}$ whit the characteristic scale length to fixed to the fiducial values of $\sim 5000$ AU.Comment: 9 pages, 5 figures, accepted for publication in Phys. Rev.

Women and Reparations

Reparations for victims of gross human rights violations are becoming an increasingly acknowledged feature in post-authoritarian and post-conflict societies coping with the legacy of a violent past. Despite some recent progress much more work needs to be done for massive reparations programs to respond better to the needs of women. This article, resting as it does on a comprehensive conception of reparations, outlines both the procedural and substantive components of reparations programs necessary for the programs to fulfill the goal of providing (partial) justice to women