While physicists have long debated gravity, with some suggesting that is may not be a fundamental force after all, the theory of emergent gravity has arisen over time, but a new study shows that this theory may actually have a fatal flaw in it.
The theory of emergent gravity links thermodynamics and gravity, but it has certainly had its fair share of critics, as Phys.org reports. Some physicists have proposed that gravity is merely what happens when tiny pieces of information end up on holographic screens which are technically spacetime surfaces. However, new research has shown that the holographic screen surfaces that underpin this theory do not act in a way that is thermodynamically appropriate.
Physicist Zhi-Wei Wang, who works at China’s Jilin University, has explained that the results of the new study will make proponents of the theory of emergent gravity have to work much harder to back up their claims.
“Emergent gravity has very strong claims: that it can explain things like dark matter and dark energy, but also reproduce the decades of work coming out of regular general relativity. That last claim is now knocked on its head by our work, so emergent gravity proponents will have their work cut out for themselves in showing consistency with the huge canon of observational results. We’ve set them back, not necessarily knocked them out.”
— Phys.org (@physorg_com) August 10, 2018
The surfaces that physicists are referring to are two-dimensional areas that can be found in spacetime. Many of these surfaces are thermodynamic in nature, like the horizons that reside around black holes. Because of this, black holes will always be beholden to thermodynamic principles. These principles include both entropy and positive temperatures.
However, some physicists believe that the surfaces of objects that do not have horizons at all may also follow the principles of thermodynamics, including the theory of emergent gravity and its holographic screens.
In their new study, researchers looked closely at a variety of different surfaces and tested these in order to determine if they too followed the first law of thermodynamics, which relates specifically to energy conservation. It was discovered that while areas around black holes did indeed follow this law, surfaces like holographic screens simply did not.
The University of York’s Samuel L. Braunstein noted that in their new research, physicists looked for ways in which they could replicate work done in the 1970s on black holes.
“We spent a large amount of time working out how to reproduce the original results for black holes from the 1970s. Although the methods from the 1970s were extremely tedious to replicate in detail, we found them very powerful and are thinking now about whether there is any way to generalize these results to other scenarios. Also, we think that our formula for the deviation away from the first law as one moves away from horizons will have important implications for quantum gravity.”
The new study on how there could be serious flaws behind the theory of emergent gravity has been published in Nature Communications.