Speaker
Description
We investigate two relativistic effects—the Shirokov effect and the Shapiro delay—within the Zipoy–Voorhees spacetime (q-metric), a generalization of the Schwarzschild solution that incorporates a quadrupole moment. By analyzing the geodesic deviation equations, we demonstrate that the quadrupole parameter induces oscillatory dynamics of test particles, with oscillation periods coinciding with the orbital period in the rotating reference frame. This behavior fundamentally distinguishes the q-metric from the Schwarzschild case and provides new insight into how multipolar structures modify orbital motion. Furthermore, we derive the Shapiro time delay in the q-metric and show its explicit dependence on quadrupole deformations of spacetime, finding a significant first-order contribution in contrast to some recent results. These findings deepen the understanding of how deviations from spherical symmetry affect gravitational phenomena such as orbital dynamics, time delay, and lensing. The results are of interest for astrophysical applications, particularly in the study of neutron stars, naked singularities, and black hole mimickers with strong quadrupole moments. Future observational tests, including pulsar timing and spacecraft tracking, may help to place further constraints on such deviations in strong gravitational fields.