Narrow Results

The nonlinear Euler–Heisenberg interaction bends light toward an electric charge. The bending angle and trajectory of light in a Coulombic field are computed in geometric optics.

We take another look at the equations behind the description of light bending in a Universe with a cosmological constant. We show that even within the impact parameter entering into the photon's differential equation, and which is defined here with exclusive reference to the beam of light as it bends around the central mass, lies the contribution of the cosmological constant. The latter is shown to enter in a novel way into the equation. When the latter is solved our approach implies, beyond the first two orders in the mass-term and the lowest-order in the cosmological constant, a slightly different expression for the bending angle from what is previously found in the literature.

In 1911, Einstein proposed that light bending by the Sun’s gravitational field could be measured during a total solar eclipse. The first opportunity in which this measurement would be tried was during the total solar eclipse of October 10, 1912. We report about the expeditions sent to Brazil to observe this eclipse, including the one from the Córdoba Observatory, from Argentina, which aimed to measure this Einstein’s effect.

It appears that studying data from the catalogue of Gamma-Ray Bursts (GRBs) can be used to examine the birefringence phenomenon in the magnetosphere of the magnetars. By analysing the data from the McGill Online Magnetar and HEASARC Fermi Burst Catalogues, in this work we studied the angular distances between GRBs and magnetars in projection, we built their distribution map by the end of 2020, and the relative lag time periods of lights coming from GRBs and magnetars. It is confirmed that there are 29 galactic magnetars and their candidates, while the other two are located out of the Milkyway. The maximum separation angle for GRB and Magnetar projectiles was 3.76 degrees (4U0142+61 and GRB110818860), while minimum angular resolution was 0.54 degrees (SGR 1627-41 and GRB090829672). Currently, we discuss the relationship of GRB light intensity by their lag time as it would come after bending in the magnetosphere of the magnetar.

Higher-derivative gravity, i.e. the system defined by General Relativity’s Lagrangian augmented by curvature-squared terms, is a renormalizable gravity model, along with its matter couplings. This model has two free parameters, α and β, which couple the higher-order terms R² and $R_{\mu \nu }^2$, respectively. In this work we study the bending of light in the framework of higher-derivative gravity utilizing both classical and semiclassical approaches. We show that the Ricci-squared sector is associated to a repulsive interaction and, at the tree-level, yields dispersive propagation of photons yet in first order. Also, a comparison between the predicted results and experimental data allows us to set an upper bound on the coupling constant β.

We address the bending of light when the quantum electrodynamic vacuum is modified by non-charge-like sources. The magnetic field of a neutron star can make a gradient for the index of refraction from the nonlinear electrodynamic effect. We calculate the bending angle when a light ray passes around a magnetized neutron star. We also calculate the bending of light by a black body radiation assuming that a neutron star is an isothermal black body. We estimate the order of magnitude for both bending angles and compare them with the bending angle by gravitation.