No matter what dark matter is, there can be no vacuum in the universe. All kinds of particles are filled with air and other objects. It's just that there are too few particles in some places. If the dense places are taken as a reference, there are few particles in other places, which can be almost ignored. Therefore, in order to facilitate the distinction and calculation, we generally call it sparse vacuum, which is actually just an ideal model and does not exist in reality. This is a very basic question, because if you want to use an ideal mathematical model, the answer to this question must be very complicated. This is the result of a lot of research work by mathematicians and computers. At present, a large number of mathematical models and studies have achieved results in this regard.
An ideal vacuum is absolutely impossible, because everything in a vacuum is infinite and weightless. Everything runs in an absolute vacuum. There is all matter, all energy, all antimatter in this absolute vacuum, and everything is a vacuum. Only space is a vacuum. This is why there is no gravity in a vacuum.
In our minds, space-time is generally composed of particles and antimatter. But in fact, the particle size is much larger than that of antimatter, so the vacuum is limited, and the antimatter particle size is much larger than that of antimatter in vacuum. We know that charge and mass are mutually transformed. The charge is in the nucleus, and the nucleus is in the electron nucleus. The nucleus is at the periphery of the electron, the charge of the nucleus is inside the surrounding molecules, and the mass of the electron is distributed inside the whole electron.