Einstein’s general relativity is an exceptional theory of gravity that has been proven correct time and time again. Quantum mechanics takes care of the three other fundamental forces, and it too has been exceptionally successful over the last century. Unfortunately, the two don’t work together. Many solutions have been proposed to get to the elusive quantum gravity, and the latest one, proposed by Professor Ginestra Bianconi, uses the fascinating concept of entropy.
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Entropy is a quantity that comes from thermodynamics. It is associated with the disorder of a system, and in an isolated system, such as the universe, it always increases. Entropy is also associated with information. For this reason, it is in the field of quantum information theory that this new work hopes to find a reconciliation between relativity and quantum mechanics.
The concept of quantum relative entropy is used in this work to describe the behavior between spacetime geometry and matter. In many graphics about gravity, the spacetime geometry is visualized as a grid, with the matter being the object curving said grid. In reality, the geometry is defined by the metric of spacetime, and it is in three space dimensions and one time dimension, all affected by the mass of objects.
However, this study suggests that the effect of said masses should be defined with a similar but different metric not related to spacetime. The connection between the geometric spacetime and the “geometric” matter field is quantified by an entropic action. Relativity is already pretty complicated, and this might seem to add another level of complexity, but if we are not talking about enormous masses or energies, these two metrics end up being the standard relativity that has been tested time and time again.
But that is not all. This theory has features that could explain both dark energy and dark matter, the unknown and hypothetical components of the universe that are at the core of our cosmology. The theory predicts the emergence of a small positive cosmological constant; this could be consistent with versions of dark energy, which is responsible for the accelerated expansion of the universe.
There is also a quantity in this theoretical framework called the G-field that modifies gravity in a way that could be consistent with dark matter. The existence of dark matter is presumed due to the motion of galaxies, suggesting a lot more invisible matter than what we can see. But maybe it’s the laws of gravity that are wrong.
“This work proposes that quantum gravity has an entropic origin and suggests that the G-field might be a candidate for dark matter,” Professor Bianconi, from Queen Mary University, said in a statement. “Additionally, the emergent cosmological constant predicted by our model could help resolve the discrepancy between theoretical predictions and experimental observations of the universe’s expansion.”
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A paper describing this innovative framework is published in the journal Physical Review D.
Source Link: Gravity From Entropy? Bold New Approach Hopes To Bring Relativity And Quantum Mechanics Together