Retrograde versus prograde models of accreting black holes

TL;DR

This paper compares retrograde and prograde models of accreting black holes, analyzing their differences in explaining energetic phenomena, and discusses how observational data can distinguish between these models.

Contribution

It provides a critical comparison of retrograde and prograde black hole accretion models, highlighting their differences and observational implications.

Findings

Retrograde models offer alternative explanations for black hole energetics.

Observational data can help distinguish between retrograde and prograde models.

The paper discusses the limitations of current numerical simulations.

Abstract

There is a general consensus that magnetic fields, accretion disks, and rotating black holes are instrumental in the generation of the most powerful sources of energy in the known universe. Nonetheless, because magnetized accretion onto rotating black holes involves both the complications of nonlinear magnetohydrodynamics that currently cannot fully be treated numerically, and uncertainties about the origin of magnetic fields that at present are part of the input, the space of possible solutions remains less constrained. Consequently, the literature still bears witness to the proliferation of rather different black hole engine models. But the accumulated wealth of observational data is now sufficient to meaningfully distinguish between them. It is in this light that this critical paper compares the recent retrograde framework with standard "spin paradigm" prograde models.