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

Understand

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.