Particle Creation by Black Holes by Stephen Hawking

Particle Creation by Black Holes

What's this about?

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

Classically, black holes can only absorb particles, not emit them. But quantum effects could cause emission.

Black Hole Temperature

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

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

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

As black holes shrink, they get hotter and emit faster. This can cause explosions releasing huge energy.

Area Decreasing Violates Classical Laws

Classically, a black hole's area can't decrease. But the emission violates this, implying negative energy flow across horizon.

Quantum Fluctuations Cause Uncertainty

The area decrease is due to quantum uncertainty in the horizon position, not observable negative energy.

Emission Matches Thermal Temperature

Hawking showed the emission matches a thermal spectrum at temperature T, supporting thermodynamic links between T, entropy, and surface gravity.

Angular Momentum and Charge

Rotation and charge affect T. Emission carries away angular momentum and charge. Superradiance causes enhanced emission for some modes.

Back Reaction On the Metric

The emission causes the black hole to evolve, not remain stationary. But the approximation works until the black hole becomes very small.

Conclusion

Quantum particle emission causes black holes to eventually evaporate away due to an underlying thermodynamic relationship between temperature, entropy, and surface gravity.

Key References

   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.