Black holes, Planckian granularity, and the changing cosmological `constant'

TL;DR

This paper proposes that Planck-scale space-time granularity causes energy diffusion, which could generate the cosmological constant and influence black hole properties, potentially resolving the H0 tension and black hole spin discrepancies.

Contribution

It introduces a novel diffusion mechanism from quantum gravity effects that impacts cosmological and black hole phenomena, linking them through a common underlying process.

Findings

Diffusion mechanism can produce observed cosmological constant magnitude

Black hole energy diffusion may explain low spin measurements

Potential resolution of H0 tension via quantum gravity effects

Abstract

In a recent work we have argued that nosy energy momentum diffusion due to space-time discreteness at the Planck scale (naturally expected to arise from quantum gravity) can be responsible for the generation of a cosmological constant during the electro-weak phase transition era of the cosmic evolution. Simple dimensional analysis and an effectively Brownian description of the propagation of fundamental particles on a granular background yields a cosmological constant of the order of magnitude of the observed value, without fine tuning. While the energy diffusion is negligible for matter in standard astrophysical configurations (from ordinary stars to neutron stars) here we argue that a similar diffusion mechanism could, nonetheless be important for black holes. If such effects are taken into account two observational puzzles might be solved by a single mechanism: the `$H_0$ tension' and the relatively low rotational spin of the black holes detected via gravitational wave astronomy.