Why did the universe form a filament structure?
The filament structure is the outcome of a universe that starts with initial density fluctuations of matter (both normal and dark). Some regions randomly happen to have a bit higher density of matter than other regions. Then these regions attract other matter preferentially, and get yet denser; then they attract yet more matter, and so on. The specific way in which this happens, and the resulting patterns- the sizes and shapes of filaments and lumps – depend on initial density fluctuations and the properties of and interactions between the particles. As you could see from the simulations, when we simulate the overall patterns of structure using what we know about matter and dark matter, they come out to be fairly similar to the observed pattern of matter.
