Physicists from Austria and Australia have described Einstein's principle of equivalence within the framework of quantum mechanics. This discovery, possibly, will allow resolving the contradictions that arise when trying to create a unified theory describing gravitational and other types of fundamental interactions. The article of scientists was published in the journal Nature Physics.
According to the principle of equivalence, in a uniform gravitational field (on the surface of the Earth), all bodies move in the same way as if they were in a uniformly accelerated coordinate system in the absence of gravitation (an elevator accelerating in empty space). In other words, gravitational and inertial masses are equal. This principle also explains why all bodies, regardless of mass, fall to the ground with the same acceleration. To move bodies with a large mass requires a significant force, but they are attracted by gravity more strongly than light objects.
The principle of equivalence underlies Einstein's general theory of relativity, but it is applicable only to the macrocosm. Quantum mechanics, which explains the fundamental interactions in the microworld, and the theory of gravity turned out to be incompatible, although each describes physical phenomena as accurately as possible on the appropriate scales. This is partly due to the fact that it was not known how the principle of equivalence can be applied to fundamental particles, which, for example, can be in superposition - simultaneously in two mutually exclusive energy states.
In a new work, scientists have shown that the principle of equivalence can be fulfilled in the quantum world. The new formulation allows for a superposition of energy states, and, since energies can be expressed in terms of mass, a superposition of masses. Thus, physicists have postulated an equivalence between the particle's rest mass, inertial mass, and gravitational mass. However, the scientists note that experimental research will be required to prove the principle.