Entropy and Black Holes: Understanding the Second Law of Thermodynamics

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SUMMARY

The discussion centers on the relationship between entropy and black holes in the context of the second law of thermodynamics. It establishes that in a closed system, the entropy S1 of a black hole at the initial state must be less than or equal to the entropy S2 of the system after the black hole has radiated away. The conclusion drawn from W. H. Zurek's work indicates that the final entropy S2 is approximately 4/3 times the initial entropy S1, resolving the confusion regarding the entropy evolution in gravitational systems.

PREREQUISITES
  • Understanding of the second law of thermodynamics
  • Familiarity with black hole thermodynamics
  • Knowledge of entropy concepts in physics
  • Basic grasp of quantum mechanics and particle physics
NEXT STEPS
  • Study W. H. Zurek's paper, "Phys. Rev. Lett. 49 1683 (1982)" for detailed insights on black hole entropy
  • Explore the implications of black hole radiation on entropy and information theory
  • Research the role of gravity in thermodynamic systems
  • Investigate the relationship between entropy and particle distribution in closed systems
USEFUL FOR

This discussion is beneficial for physicists, students of thermodynamics, and researchers interested in black hole physics and entropy dynamics.

jmcmahon
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I am a little confused over something, so perhaps someone can tell me which one of the following statements is incorrect. (I don't know a lot about this, so forgive my ignorance).

Suppose that we have a closed system of some size, and we start in a state where we have a black hole at the center. So there is some entropy S1 at our initial condition. Now we let the system evolve and the black hole starts radiating and losing mass. At some point very far in the future the black hole radiates completely away and we are left with a lot of particles that are distributed (uniformly?) throughout our system. Our final condition here has some entropy S2. The second law of thermodynamics says that S2 >= S1. However, it was my understanding that in the presence of gravity a large number of particles uniformly distributed will have a lower entropy that when they are clumped together (like our original black hole). So it seems like S1 < S2. Or are so many particles created during the radiation that S2 > S1?
 
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It looks like Zurek figured out the answer some time ago. The answer is that the end entropy is ~4/3 times the initial entropy.

For anyone else interested in this, see W. H. Zurek, Phys. Rev. Lett. 49 1683 (1982).
 

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