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Study Finds Flaw In Emergent Gravity https://phys.org/news/2018-08-flaw-emergent-gravity.html
An anonymous reader quotes a report from Phys.Org:
In recent years, some physicists have been investigating the possibility that gravity is not actually a fundamental force, but rather an emergent phenomenon that arises from the collective motion of small bits of information encoded on spacetime surfaces called holographic screens. The theory, called emergent gravity, hinges on the existence of a close connection between gravity and thermodynamics. Emergent gravity has received its share of criticism, however, and a new paper adds to this by showing that the holographic screen surfaces described by the theory do not actually behave thermodynamically, undermining a key assumption of the theory.
In the new paper, the scientists tested whether different kinds of surfaces obey an analogue of the first law of thermodynamics, which is a special form of energy conservation. Their results reveal that, while surfaces near black holes (called stretched horizons) do obey the first law, ordinary surfaces -- including holographic screens -- generally do not. The only exception is that ordinary surfaces that are spherically symmetric do obey the first law. As the scientists explain, the finding that stretched horizons obey the first law is not surprising, since these surfaces inherit much of their behavior from the nearby horizons. Still, the scientists caution that the results do not necessarily imply that stretched horizons obey all of the laws of thermodynamics. On the other hand, the finding that ordinary surfaces do not obey the first law is more unexpected, especially as it is one of the key assumptions of emergent gravity. Going forward, researchers will work to understand what this means for the future of emergent gravity, as well as explore other possible implications. |
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