Planck stars, White Holes, Remnants and Planck-mass quasi-particles. The quantum gravity phase in black holes' evolution and its manifestations (2407.09584v4)

Abstract: This is a review of some recent developments on quantum gravity aspects of black hole physics. In particular, we focus on a scenario leading to the prediction of the existence of a Planck-mass quasi-stable object, that could form a component of dark matter.

• The paper proposes that quantum gravity effects drive black hole evolution, suggesting transitions through Planck stars or white holes that resolve the information paradox and yield stable remnants.
• These quasi-stable remnants, theoretically linked to Loop Quantum Gravity and general relativity, are suggested as potential constituents of dark matter.
• The study challenges classical views on black holes and suggests new empirical searches for dark matter, potentially redefining our understanding of gravity and universal composition.

An Analysis of Planck Stars, White Holes, Remnants, and Planck-Mass Quasi-Particles in Quantum Gravity

The paper discusses significant advances in quantum gravity and their implications for black hole physics. The primary focus is on the potential existence of quasi-stable Planck-mass objects, which may manifest as remnants of evaporated black holes. Such remnants are theoretically predicted to contribute to dark matter, leveraging core principles of Loop Quantum Gravity (LQG) and general relativity (GR).

Quantum Gravity Effects and Black Hole Evolution

Black holes are traditionally understood within the framework of classical general relativity. However, this perspective becomes inadequate in regions of extremely high curvature, particularly the black hole's interior. Within this context, quantum gravity effects cannot be ignored. The authors propose that black holes may evolve into regions governed by such effects, undergoing transitions that lead to the formation of Planck-mass particles, referred to as remnants.

Incorporating LQG insights, the paper suggests that these remnants arise from the transition of black holes into white holes, through a process analogous to quantum tunneling. This transition is purported to offer a resolution to the black hole information paradox by allowing the trapped quantum information to be released gradually, post-evaporation.

Theoretical Underpinnings and Models

The paper explores three key theoretical aspects supporting this scenario:

1. Planck Stars and Quantum Bounces: The authors posit that a collapsing black hole reaches a stage where quantum gravitational pressure halts further collapse, causing a rebound or bounce—a state referred to as a "Planck star."
2. Black-to-White Hole Transition: Leveraging solutions from LQG, a transition from a black hole to a white hole is depicted as a feasible quantum event. This process is highly dependent on the mass of the black hole, with a probability akin to quantum tunneling that is exponentially suppressed for masses much larger than the Planck mass.
3. Semiclassical Models and Stability: The analysis attributes quantum stability to remnants, including effects such as a superposition of black and white hole states resulting from LQG's area quantization. The superimposed states enhance stability by delocalizing the extrinsic curvature characteristics between black and white phases, preventing decay into classical configurations.

Implications and Speculative Aspects

The paper makes several bold proposals:

• Dark Matter Constituents: By linking the characteristics of these remnants to dark matter, the paper suggests a natural candidate for dark matter that avoids new physical laws or particles.
• Observational Prospects: The existence of quasi-stable remnants opens paths for empirical exploration, potentially altering searches for dark matter and contextualizing gamma-ray observations.
• Conceptual Shifts: It challenges traditional perspectives on the nature of black holes, proposing a paradigm shift in understanding their lifecycle by integrating quantum mechanics into GR.

Critique and Conclusion

The amalgam of LQG and GR findings presented in this research offers a cohesive theoretical outlook on remnants and white holes. While the hypotheses and models are speculative, they are grounded in an established theoretical framework, offering a non-trivial avenue for exploring the interface of quantum mechanics and general relativity. The potential direct observational consequences of these remnants require extensive empirical scrutiny. Long considered theoretical constructs, remnants and white holes may redefine our comprehension of the universe's composition and the fundamental nature of gravity. The paper sets a precursor for further exploration into black hole thermodynamics, quantum gravity phenomenology, and cosmological model re-evaluation.