Radiation from black holes
Pro Research Analysisby 
Searched over 200M research papers
Radiation from Black Holes: A Comprehensive Overview
Electromagnetic and Gravitational Radiation from Particles Falling into Black Holes
When charged particles fall into a neutral Schwarzschild black hole, they emit significant electromagnetic radiation. For particles with zero angular momentum, a system of electrons emits ten times more electromagnetic radiation compared to gravitational radiation. This ratio decreases for particles with a higher mass-to-charge ratio than electrons. In the case of particles in a spiraling circular orbit, the energy emitted remains the same for both charged and uncharged particles, but the spiral time is significantly shorter for charged particles. This introduces a new radiation mechanism for black holes, as the spiral time for uncharged particles emitting gravitational radiation is prohibitively long, making such processes practically non-existent .
Radiation from Extremal Black Holes
Extremal Reissner-Nordström black holes, characterized by their maximum charge-to-mass ratio, emit charged particles but no neutral scalar radiation. This emission is consistent with the predictions of Euclidean theory, which suggests the absence of thermal effects. The entropy considerations for these black holes differ from those of eternal extreme black holes due to the emission of charged particles .
Quantum Optics and Acceleration Radiation
Using quantum optics and general relativity, it has been shown that atoms falling into a black hole emit radiation that resembles, but is distinct from, Hawking radiation. This radiation, termed horizon brightened acceleration radiation (HBAR), provides insights into the Einstein principle of equivalence between acceleration and gravity. The entropy associated with this radiation is different from the traditional Bekenstein-Hawking black hole entropy .
Nonthermal Radiation from Evaporating Black Holes
Black hole evaporation, driven by the creation of entangled particle-antiparticle pairs near the event horizon, results in nonthermal radiation. The entanglement between photons inside and outside the event horizon and the non-unitary absorption of negative energy photons near the black hole center alter the outgoing radiation. This process ensures that the radiation carries information about the black hole's interior, preserving entropy during evaporation .
Quantum Radiation from Nonsingular Black Holes
Studies on quantum radiation from evaporating nonsingular black holes, using a modified Hayward metric, reveal significant quantum energy radiation from the inner domain of the black hole. This radiation can be exponentially large due to the mass inflation effect, but can be mitigated by choosing an appropriate redshift function. The emitted energy can exceed the initial mass of the black hole, highlighting the importance of back-reaction effects in constructing a self-consistent model of a nonsingular evaporating black hole .
Quantum Radiation from Sandwich Black Holes
In a sandwich black hole model, where a black hole is formed by the collapse of a null shell and later disrupted by another shell with negative mass, the radiation emitted after the black hole's formation closely matches Hawking radiation. The radiation from the black hole's interior peaks when the second shell intersects the inner horizon, with the energy outburst being exponentially large in the standard metric. This effect is suppressed in a modified metric with a non-trivial redshift parameter, reducing the surface gravity of the inner horizon .
Hawking Radiation and Dark Matter Production
Hawking radiation from primordial black holes in the early universe could produce both dark radiation and dark matter. If the early universe experienced a black hole-dominated era, Hawking radiation could generate dark radiation at levels that help reconcile discrepancies in Hubble constant measurements. Additionally, dark matter produced in this manner would need to be extremely heavy to match observed abundances .
Information Preservation in Black Hole Radiation
The information paradox, which questions whether information is lost in black hole radiation, suggests that information could be encoded in the radiation itself. This information might be released very slowly or be so spread out that it remains undetectable in perturbative analyses. The concept of "dark information," stored in correlations among non-thermally radiated particles, is influenced by dark energy, which lowers the Hawking temperature and extends the black hole's lifetime. This enhances the non-thermal effects of radiation, increasing the stored dark information 910.
Conclusion
The study of radiation from black holes encompasses a wide range of phenomena, from electromagnetic and gravitational radiation to quantum effects and information preservation. These insights not only deepen our understanding of black hole physics but also have implications for broader cosmological questions, such as the nature of dark matter and the fundamental principles of quantum mechanics and general relativity.
Sources and full results
Most relevant research papers on this topic