Creating a black hole
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Creating a Black Hole: Mechanisms and Theoretical Insights
Black Hole Creation in 2 + 1 Dimensions
In three-dimensional gravity with a negative cosmological constant, black holes can be created when two point particles approach each other with sufficient center-of-mass energy. This process results in the formation of a BTZ black hole, as demonstrated by an explicit solution to the Einstein equations. This solution describes the collapse of two massless particles into a non-rotating black hole, and it is suggested that massive particles could also be used to create rotating black holes.
Pair Creation of Rotating Black Holes
The creation of rotating black holes can also occur in the presence of an external electromagnetic field. Using the Ernst technique in Einstein-Maxwell gravity, a solution describing a pair of charged and spinning black holes is generated. This process involves a wormhole instantonic solution that interpolates between the two black holes, discussing the quantum process of creation rate in an external magnetic field.
Quantum Creation of Black Holes
Quantum Cosmology and Black Hole Formation
In quantum cosmology, black holes can be created from nothing, originating from a constrained gravitational instanton. The probability of creating various types of black holes in the Kerr-Newman family is related to the total entropy of the universe, which is the exponential of one quarter of the sum of the areas of both the black hole and cosmological horizons. Similarly, using the Hartle-Hawking no-boundary proposal, the wave function and probability of a single black hole created at the birth of the universe can be studied. This black hole originates from a generalized gravitational instanton with conical singularities, and the probability of its creation is also tied to the total entropy of the universe.
Black Hole Creation During Inflation
During the inflationary period of the universe, black holes can be created through quantum processes. A single topology change can lead to the formation of multiple black holes, which eventually evaporate and cause the universe to fragment. This iterative process can lead to the proliferation of inflationary universes.
Particle Creation by Black Holes
Black holes, contrary to classical theory, can emit particles due to quantum mechanical effects. This emission, akin to black body radiation, leads to a slow decrease in the mass of the black hole and its eventual disappearance. This process, known as Hawking radiation, shows that black holes can create and emit particles, violating the classical law that the area of the event horizon cannot decrease. However, a Generalized Second Law is maintained, where the sum of the entropy of matter outside black holes and one quarter of the event horizon area never decreases .
Primordial Black Holes from Phase Transitions
Primordial black holes (PBHs) can form via a first-order electroweak phase transition (FOEWPT). This process involves the collapse of non-topological solitons called Fermi-balls, which form by trapping fermions in the false vacuum during the FOEWPT. These solitons eventually collapse into PBHs due to internal Yukawa attractive forces. This mechanism suggests that PBHs could be candidates for dark matter, with experimental signals including FOEWPT gravitational waves and multi-lepton/jet or displaced vertex final states at the LHC.
Conclusion
The creation of black holes can occur through various mechanisms, including high-energy particle collisions, quantum cosmology, and phase transitions in the early universe. These processes are deeply rooted in both classical and quantum theories of gravity, providing a rich field of study for understanding the fundamental nature of black holes and their role in the cosmos.
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