Non-singular Gravitational Collapse Avoids Singularity, Rebounds, and Deviates from Hawking Radiation

Recent investigations into gravitational collapse reveal important corrections to established theories, and challenge the expectation of inevitable singularities. Hassan Mehmood, from the University of New Brunswick, and colleagues explore what happens when a collapsing star doesn’t fall into a singularity, but instead bounces back, potentially avoiding the breakdown of known physics. Their work examines particle creation during this non-singular collapse, demonstrating that the spontaneous emission of particles differs from the well-known Hawking radiation predicted by classical models. This deviation from expected thermal behaviour suggests a fundamental shift in our understanding of black hole evaporation and offers a potential mechanism for resolving problematic shell crossing singularities within collapsing dust clouds.

Bouncing Black Holes and Hawking Radiation Correction

Recent research explores how quantum gravity modifies gravitational collapse, where matter compresses under its own weight. Instead of collapsing into a central singularity, collapsing matter may bounce and expand outwards, contrasting with classical predictions. Understanding this bounce and its impact on emitted radiation is crucial for developing a complete theory of quantum gravity and resolving the singularity problem. This research investigates how corrections to Hawking radiation, the thermal radiation emitted by black holes, arise from this non-singular collapse model, aiming for a more accurate description of the radiation spectrum and its characteristics.

The research demonstrates that the probability of particle emission during this bouncing collapse differs from that of Hawking radiation from classical collapse, implying a non-thermal radiation spectrum. This non-singular collapse could potentially resolve issues with shell crossing singularities, points where infalling matter becomes infinitely dense.

Loop Quantum Gravity Resolves Black Hole Singularity

This research investigates the quantum behavior of black holes, specifically their evaporation process and the fate of the singularity at their core, aiming to resolve the information paradox and develop a consistent theory of quantum gravity. A key framework used is Loop Quantum Gravity, a theoretical approach that attempts to quantize spacetime itself. Researchers are exploring how Loop Quantum Gravity modifies the classical picture of black hole collapse and evaporation.

A major focus is finding mechanisms within Loop Quantum Gravity that can resolve the singularity, replacing it with a quantum-geometric structure. The research often focuses on effective spacetime descriptions, approximations valid at certain energy scales. Hawking radiation is explained as arising from quantum tunneling, and path integrals are used to calculate probabilities related to black hole evaporation and quantum effects.

The Wentzel-Kramers-Brillouin approximation connects classical and quantum descriptions, while isolated and dynamical horizons provide frameworks for studying black holes in general contexts. During gravitational collapse, infalling matter can form shells that may lead to shocks, regions of rapid change in density and velocity. Loop Quantum Cosmology, an application of Loop Quantum Gravity to cosmology, is used to study the early universe.

The research suggests that Loop Quantum Gravity can resolve the singularity by replacing it with a quantum bounce or a non-singular region, leading to modified predictions about the radiation spectrum and the fate of the black hole. The dynamics of shockwaves formed during gravitational collapse may not be unique, and researchers are exploring whether quantum black holes completely evaporate or leave behind a remnant. This research provides a generalized analysis of dust collapse within effective Loop Quantum Gravity, focusing on the fate of shocks and their consistency, and explores radiation emitted from the inner horizon of a black hole.

Bouncing Collapse Modifies Hawking Radiation Spectrum

This research investigates particle creation during gravitational collapse, challenging aspects of the standard Hawking radiation model. The findings demonstrate that when considering non-singular collapse, where the collapsing body bounces rather than forming a singularity, the probability of particle emission differs from that predicted by classical Hawking radiation, indicating a deviation from a purely thermal spectrum. This suggests that modifications to classical gravitational collapse, motivated by considerations from quantum gravity, can alter the expected radiation profile.

The study highlights that the standard picture of Hawking radiation relies on the assumption of a singularity forming during collapse, an assumption that may not hold in more complete theories. Future research could focus on further exploring the implications of these non-thermal spectra and refining models of quantum gravity to accurately describe the late stages of gravitational collapse.