Holographic principle? The result that the entropy of a quantum field within a bounded volume is proportional to the surface area was derived (I recall) by Friedman and Sorkin, and then applied by Jay Beckenstein for the entropy of a Black Hole. Beckenstein also derived the temperature of a BH from these thermodynamic pronciples, but Hawking did the calculations for a quantum field in a background BH spacetime and showed that the BH radiates with the above black body radiation temperature.

I stop to miau to cats.

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