Hi folks, an interesting and topical question: where is the dark energy responsible for the accelerating universe from?
First of all, we need to be clear that if the universe is rapidly expanding, then the energy-momentum tensor of all matter in the Universe is not conserved. As the energy-momentum tensor must be conserved, the simplest solution to this problem is to introduce a scalar field in Einstein’s equations. This scalar field checks its own equations and makes the energy-momentum tensor including all matter and scalar field conserved.
The scalar field is created by the matter itself and its energy-momentum tensor contains four functions. Three of these functions can be chosen as independent variables and can be adjusted to observational data of the accelerating expansion of the universe.
For all this, the scalar field is responsible for the accelerating expansion of the universe.
As there is a long range vector field like the electromagnetic and a long range tensor field like the gravitational, there is also a long range scalar field.
Moreover, this scalar field causes the inertia.
All this rigorously detailed in the Appendix of the section “THE PHYSICS OF TIME TRAVEL“