The theory of general relativity (GR) perfectly describes the most commonly known gravitational effects, but for two leading gravitational problems at the astrophysical and cosmological scales that cannot be explained by GR: the existence of dark matter and dark energy.
One possible way to resolve these problems is to look for alternative gravitational theories, and this is the endeavor of many researchers. One popular candidate is the so-called degenerate higher-order scalar tensor (DHOST) theories. These theories make two critical predictions: the existence of a fifth-force effect inside stars and that the speed of gravitational waves is not the speed of light.
In a recent article, Ippocratis Saltas and Ilidio Lopes explore the validity of these DHOST theories inside the sun. In particular, they explain how the effect of the fifth force on the solar interior affects the acoustic oscillations. Equally, they have constrained the parameter that measures the strength of the fifth force by using Helioseismology data: this result is a thousand times more accurate than the results of the previous measurements. This, in turn, would suggest constraints of a similar order for the theory’s free functions around a cosmological background.
If you want to know more, please follow the article link: Phys. Rev. Lett. 123, 091103