From exoplanets to gravity theory
In the recently published work titled Metric-affine gravity effects on terrestrial exoplanet profiles Phys. Rev. D 104, 084097 (2021), Aleksander Kozak, a graduate student with the Institute of Theoretical Physics, and Aneta Wojnar study the influence of changes to the gravity theory on the structure of planets with an established chemical composition.
The authors focused on the so-called Starobinski model, which is one of the simplest modifications to the general gravity theory. The Starobinski model is equivalent to the standard gravity theory combined with the propagation of real scaled degrees of freedom, suitable for driving inflation. This model was the first model of inflation, introduced by Alexei Starobinski in the 1980s.
The result demonstrated that the modification introduces a degeneration in the so-called mass-radius diagram, which illustrates the relationship between a planet’s radius and mass and its chemical composition.The degeneration refers to the uncertainty in determining the composition of a planet based only on its mass and radius. A new way to test the theory of gravity by studying the precession of the planet’s axis, which is affected by the internal structure of the object, was also described.
Added by: Joanna Molenda-Żakowicz
Dean’s representative for faculty promotion and media relations
