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Physicists from the University of Aalto in Finland have proposed a new view of gravity, which they say is compatible with the Standard Model elementary particles and can bring scientists closer to the so-called «Theory of Everything».
For a long time, scientists have been trying to combine general relativity, which describes gravity as curvature of space-time under the influence of mass and energy, with quantum mechanics and quantum field theory, which describes the behavior of elementary particles and three of the four fundamental forces (electromagnetic, weak, and strong nuclear interactions) through the exchange of quanta. These two theories are not very compatible with each other.
Attempts to apply the rules of quantum mechanics to gravity, or vice versa, to add gravity to the Standard Model of Particle Physics, encounter mathematical paradoxes that cannot be resolved by traditional methods. In this regard, physicists Mikko Partanen and Jukka Tulkki have proposed an intermediate step that could help to combine these two theories.
The scientists’ proposal is to consider gravity as a gauge field. The concept of «Gauge Theory» belongs to quantum field theory, which describes behavior of elementary particles in a certain field. For example, charged particles interact by exchanging photons, which are quanta of the electromagnetic field. This field is the calibration field.
«The best known calibration field is the electromagnetic field. When electrically charged particles interact with each other, they interact with the help of an electromagnetic field, which is the corresponding calibration field. Therefore, when we have particles with energy, the interactions they have due to this energy will occur through the gravitational field», — explains Jukka Tulkki.
That is, particles have energy, and their gravitational interaction should occur through the exchange of some hypothetical carrier particles — quanta of the gravitational field. The peculiarity of what the finnish scientists proposed is a shift in emphasis to symmetry. The standard model of particle physics is based on mathematical symmetries. At the same time, general relativity is based on the symmetry of space-time. Mikko Partanen and Jukka Tulkki proposed to build a quantum theory of gravity based on symmetries similar to those that underlie the Standard Model.
Why is all this necessary? The fact is that existing theories stop working in extreme conditions. For example, general relativity predicts that at the center of black holes there should be a singularity — a point with infinite density and curvature of space-time. However, the general theory does not explain what actually happens there, and quantum mechanics does not have the appropriate apparatus for this either.
To explain what happened in the first moments after the Big Bang, when the Universe was a combination of ultra-high energies and densities, and gravity was equal in strength to other types of interaction. Back then, quantum effects could have played a key role for it. To understand all this, scientists need a full-fledged theory of quantum gravity. The asymmetry of matter and antimatter: why does our world consist of matter and almost no antimatter, even though they should have been formed equally during the Big Bang?
At the same time, the scientists themselves admit that their work is still far from a full-fledged theory of quantum gravity. The theory proposed by the Finnish physicists works well in the first-order approximation. However, it is unclear whether it will work with more complex interaction variants.
The results of the study are published in the journal Reports on Progress in Physics
Source: ScienceAlert