Horizon quantum geometries and decoherence

TL;DR

This paper explores how quantum geometric effects of black hole horizons, such as area quantization, influence decoherence phenomena, potentially reducing decoherence effects significantly depending on the quantum of area.

Contribution

It introduces the impact of horizon area quantization on decoherence, showing that quantum geometry can suppress decoherence effects compared to classical horizon models.

Findings

Quantum geometry can significantly reduce decoherence effects.

Discreteness of horizon area levels impacts decoherence strength.

Decoherence can become negligible with area quanta of order Planck length squared.

Abstract

There is mounting theoretical evidence that black hole horizons induce decoherence on a quantum system, say a particle, put in a superposition of locations, with the decoherence functional, evaluated after closure of the superposition, increasing linearly with the time the superposition has been kept open. This phenomenon has been shown to owe its existence to soft modes, that is modes with very low frequencies, of the quantum fields -- sourced by the particle -- which pierce through the horizon, or also can be understood as coming from the interaction with the black hole described as a thermodynamic quantum system at Hawking's temperature. Here we investigate the effects of ensuing quantum aspects of the geometry itself of the horizon, in an effective perspective in which the quantum geometry of the horizon is captured by existence of a limit length or by horizon area quantisation. We show that the discreteness of the energy levels associated to the different geometric configurations might have strong impact on the results, in particular reducing the decoherence effects even to a negligible level in case of quanta of area $A_0 = \mathcal{O}(1) \, \, l_p^2$ or larger, with $l_p$ the Planck length.