Particle Creation by Black Holes

February 2, 2023
5:00pm to 6:00pm

Blue Room

Specialist level
Eduardo Velasco

Blue Room


Eduardo Velasco Aja will present the following paper: Particle Creation by Black Holes, by Stephen Hawking (Commun.Math.Phys. 43 (1975) 199-220). 

In the classical theory black holes can only absorb and not emit particles. However it is shown that quantum mechanical effects cause black holes to create and emit particles as if they were hot bodies with temperature   where κ is the surface gravity of the black hole. This thermal emission leads to a slow decrease in the mass of the black hole and to its eventual disappearance: any primordial black hole of mass less than about 1015 g would have evaporated by now. Although these quantum effects violate the classical law that the area of the event horizon of a black hole cannot decrease, there remains a Generalized Second Law: S+1/4A never decreases where S is the entropy of matter outside black holes and A is the sum of the surface areas of the event horizons. This shows that gravitational collapse converts the baryons and leptons in the collapsing body into entropy. It is tempting to speculate that this might be the reason why the Universe contains so much entropy per baryon. 

PDF iconHawking Particle Creation.pdf