Cosmic Mirages Test the Law of Gravity ⚡ экспресс
The mystery of the accelerated expansion of the Universe drives the search for alternative theories of gravity. f(R) models, which extend General Relativity, can reproduce the background evolution of ΛCDM without explicit dark energy but alter the growth of structures. This work investigates several viable f(R) models using weak gravitational lensing data. The impact of these theories on the matter power spectrum, as well as on convergence and cosmic shear spectra, is analyzed. Data processing is performed within a Bayesian framework using the Cobaya and MGCobaya codes, which provide consistent predictions and comparison with observational data from weak lensing and cosmic microwave background lensing. It is shown that standard cosmological parameters remain consistent with the ΛCDM scenario for all models considered, which is expected due to degeneracy at the background level. However, nontrivial and model-dependent constraints on the characteristic parameters of several f(R) theories are obtained.
Light from distant galaxies, passing through clusters of matter, gets distorted—much like the bottom of a pool breaks up into ripples of water. Astronomers measure these barely perceptible bends in shape and create a map of gravitational ‘ripples.’ This is weak lensing—a natural detector of invisible matter. However, the accelerated expansion of the cosmos is usually attributed to dark energy, but maybe it’s not there, and gravity itself on huge scales works a little differently. By testing theories where gravity gets a tiny correction, scientists overlaid them onto the distortion map. It turned out that the allowed deviations from Einstein’s law are within a few percent. To spot the difference, they had to average the shapes of millions of galaxies. If gravity were different, the night’s constellations would ‘ripple’ differently—and it would be visible. So lensing became a judge, separating permissible corrections from fantasies.
🎯 When a distant quasar, a lensing galaxy, and a telescope line up, an Einstein ring appears—a perfectly round circle of light.