Gravitational Particle Production Influences Hubble Constant Measurements

Recent research by Recai Erdem explores the phenomenon of gravitational particle production and its implications for the Hubble constant, denoted as $H_0$. The study, titled "Gravitational particle production and the Hubble tension," examines how the production of scalar particles due to gravitational effects can influence the effective cosmic energy density from the era after photon decoupling to the present.

The findings indicate that this gravitational particle production significantly affects the measured value of the Hubble constant, leading to an increase in the directly measured $H_0$. However, it does not alter the Hubble constant used in calculating the number density of baryons, which is essential for determining the recombination redshift.

This discrepancy may provide an explanation for the observed differences between local measurements of the Hubble constant and those derived from non-local measurements, such as those from the Cosmic Microwave Background (CMB). The research suggests that gravitational particle production could play a crucial role in addressing the ongoing Hubble tension, which refers to the conflict between various measurements of the universe's expansion rate.

The study is available for further reading at arXiv:2402.16791.