# Black Holes extert Pressure on Environment:

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Black holes found to exert a pressure on their environment:

Physicists at the University of Sussex have discovered that black holes exert a pressure on their environment, in a scientific first.

In 1974 Stephen Hawking made the seminal discovery that black holes emit thermal radiation. Previous to that, black holes were believed to be inert, the final stages of a dying heavy star.

The University of Sussex scientists have shown that they are in fact even more complex thermodynamic systems, with not only a temperature but also a pressure.

The serendipitous discovery was made by Professor Xavier Calmet and Folkert Kuipers in the Department of Physics and Astronomy at the University of Sussex, and is published today in Physical Review D.

the paper:

Quantum gravitational corrections to the entropy of a Schwarzschild black hole:

ABSTRACT:

We calculate quantum gravitational corrections to the entropy of black holes using the Wald entropy formula within an effective field theory approach to quantum gravity. The corrections to the entropy are calculated to second order in curvature and we calculate a subset of those at third order. We show that, at third order in curvature, interesting issues appear that had not been considered previously in the literature. The fact that the Schwarzschild metric receives corrections at this order in the curvature expansion has important implications for the entropy calculation. Indeed, the horizon radius and the temperature receive corrections. These corrections need to be carefully considered when calculating the Wald entropy.

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The first thing I needed to do was eliminate my ignorance on " Wald entropy" and the "Wald entropy formula"....

Wald's entropy is equal to a quarter of the horizon area in units of the effective gravitational coupling:

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