A paper in Physics Letters B suggests that matter's energy determines how it interacts with space-time. Particles travel through the modern universe much like light through a vacuum, but shortly after the Big Bang they might have resembled photons encountering a glass prism, with energy levels determining the way matter and space-time interact.
White light can form rainbows because it is composed of photons of different energies, which we see as different colors. A prism bends these so that all the photons of a particular energy are together, producing a spectrum. Professor Jezry Lewandowski of the University of Warsaw has proposed a way that space-time could act as a prism to create a matter rainbow, creating a rigorous version of the idea hinted at by Thomas Pynchon's popular novel Gravity's Rainbow.
"Two years ago we reported that in our quantum cosmological models, different types of particles feel the existence of space-times with slightly different properties,” Lewandowski said in a statement. "Now it turns out that the situation is even more complicated. We have discovered a truly generic mechanism, whereby the fabric of space-time felt by a given particle must vary depending not only on its type, but even on its energy,"
Physicists today are struggling to reconcile the theories of both general relativity, which so far has proven successful at explaining the behavior of gravity at large scales, and quantum mechanics, which has proven stunningly successful on the scale of the very small. Quantum theories of gravity attempt to bring these two together, proposing particles that act as messengers of gravitational fields, but have so far been unable to produce a comprehensive model.
Space-time, as the name suggests, combines three-dimensional space with time as a cohesive thing. General relativity presents it as inherently bound up with gravity.
When the authors quantized their model, assuming that only specific discrete values are possible, they found the processes they modeled behaved in the same way as if space-time is classical, where any values are possible. Other than under extreme energy conditions, quantum space-time behaves like classical space-time.
"This result is simply astonishing,” said first author Mehdi Assanioussi. "We start with the fuzzy world of quantum geometry, where it is even difficult to say what is time and what is space, yet the phenomena occurring in our cosmological model still look as if everything was happening in ordinary space-time!"
Under most circumstances particles of different energies' interactions with space-time are so similar the differences are undetectable. However, under the right conditions, such as just after the Big Bang, a sort of space-time prism could have been produced, dispersing particles by their energies into a type of gravitational rainbow. Testing is a challenge, however, since in today's universe the rainbow is so narrow that only particles larger than anything produced in the Large Hadron Collider would show a measurable effect.