Particle Creation by Black Holes by Stephen Hawking
Particle Creation by Black Holes[edit | edit source]
What's this about?[edit | edit source]
This paper by physicist Stephen Hawking discusses how black holes can create and emit particles, acting like hot bodies with a temperature.
Black Holes Should Only Absorb[edit | edit source]
Classically, black holes can only absorb particles, not emit them. But quantum effects could cause emission.
Black Hole Temperature[edit | edit source]
Hawking showed that black holes emit particles like a body with temperature T proportional to the surface gravity K of the black hole. For a solar mass black hole, T is tiny.
Quantum Particles Near Horizon[edit | edit source]
Virtual particle pairs exist near the event horizon. A negative energy particle can tunnel inside, becoming real. The positive energy particle escapes as radiation.
Emission Causes Black Holes to Shrink[edit | edit source]
This emission causes black holes to slowly shrink over billions of years. Tiny primordial black holes would have evaporated by now.
As Mass Decreases, Emission Speeds Up[edit | edit source]
As black holes shrink, they get hotter and emit faster. This can cause explosions releasing huge energy.
Area Decreasing Violates Classical Laws[edit | edit source]
Classically, a black hole's area can't decrease. But the emission violates this, implying negative energy flow across horizon.
Quantum Fluctuations Cause Uncertainty[edit | edit source]
The area decrease is due to quantum uncertainty in the horizon position, not observable negative energy.
Emission Matches Thermal Temperature[edit | edit source]
Hawking showed the emission matches a thermal spectrum at temperature T, supporting thermodynamic links between T, entropy, and surface gravity.
Angular Momentum and Charge[edit | edit source]
Rotation and charge affect T. Emission carries away angular momentum and charge. Superradiance causes enhanced emission for some modes.
Back Reaction On the Metric[edit | edit source]
The emission causes the black hole to evolve, not remain stationary. But the approximation works until the black hole becomes very small.
Conclusion[edit | edit source]
Quantum particle emission causes black holes to eventually evaporate away due to an underlying thermodynamic relationship between temperature, entropy, and surface gravity.
Key References[edit | edit source]
Hawking, Nature 248, 30 (1974) Hawking, Communications in Mathematical Physics 43, 199 (1975) Bekenstein, Physical Review D 7, 2333 (1973)
See original paper for full details and references.