How to reconcile the two pillars of modern physics: quantum theory and gravity? One or both must yield and surrender. The new approach says that gravity can emerge from random fluctuations at the quantum level, which makes quantum mechanics more fundamental of the two theories. Our two main explanations of reality, argued that quantum theory governs the interactions of the smallest particles of matter. The General theory of relativity as gravitation and the largest structures in the Universe. Since, as Einstein created his famous theory, physicists were trying to bridge the gap between them, but to no avail.
Part of the problem is knowing which strings each theory are of fundamental importance for our understanding of reality.
One approach to reconciling gravity with quantum mechanics was to show that gravity on its most fundamental level goes to the indivisible bits of quanta, like the electromagnetic forces arise from quanta called photons. But this way to a theory of quantum gravity turned out to be impassable.
And here Antoine Tilla from the Institute of quantum optics max Planck in Garching, Germany, attempted to reach the gravity, changing the standard quantum mechanics.
In quantum theory the state of a particle is described by its wave function. The wave function allows to calculate, for example, the probability of finding the particle in a particular place when measuring. Before measurement it is unknown whether there is a particle, and if so, where. The reality, apparently, is the act of observation which “destroys” the wave function.
But quantum mechanics does not define what is a measurement or observation. For example, do in this case, a conscious agent is a person? The measurement problem leads to paradoxes like schrödinger’s cat where the cat can be both alive and dead in a box until someone opens the box and do not look at it.
One solution to these paradoxes is the so-called GRW model, which was developed in the late 1980-ies. It includes “flash”, which are random spontaneous collapses of the wave function of quantum systems. The result is exactly the same as if it were measured, but no apparent observer.
Tilla has modified this model to show how it can lead to the theory of gravity. In this model, when the flash destroys the wave function and forces the particle to be in one place, it creates a gravitational field at this point in space-time. Massive quantum system with a large number of particles shows a lot of flashes, along with the fluctuations of the gravitational field.
It turns out that on average, these fluctuations one would expect the gravitational field arising from the theory of gravitation of Newton (read more about the job arxiv.org/abs/1709.03809). This approach to the unification of gravity with quantum mechanics is called semiclassical: gravity emerges from quantum processes, but it remains a classical force. “There is no reason to ignore this semiclassical approach, in which gravity remains a classic at a fundamental level,” says Tilla.
“In principle, I like this idea,” says Klaus Hornberger University of Duisburg-Essen in Germany. But he also notes that we need to solve other problems before this approach will become a serious contender for the unification of all fundamental forces underlying the laws of physics, in large and small scale. For example, the model of Tilloy can be used to obtain gravitation, described by Newtonian theory, but mathematicians have yet to determine whether it effectively to describe gravity in the framework of the General theory of relativity.
However, his model makes predictions that can be tested. For example, it predicts that gravity will behave differently at the scale of the atom and on the large scale. If the tests show that the model of Tillea to the reality and gravity collapserow really arises from quantum fluctuations, this will be an important indication that the theory of everything will include semi-classical gravity.
Gravity can create a strange flash in the quantum world
Ilya Hel