Talk:Dark matter

Dark Matter vs Modified Gravity | Sean Carroll

Da <https://www.youtube.com/watch?v=iu7LDGhSi1A>

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• This is how a 'fuzzy' universe may have looked - Fuzzy Dark Matter

Fuzzy dark matter is made up of particles that are so light that they act in a quantum, wave-like fashion, rather than as individual particles. This quantum, fuzzy nature, Mocz says, could have produced early galaxies that look entirely different from what standard models predict for cold dark matter.

"Even though in the late universe these different dark matter scenarios may predict similar shapes for galaxies, the first galaxies would be strikingly different, which will give us a clue about what dark matter is," Mocz says.

To see how different a cold and a fuzzy early universe could be, the researchers simulated a small, cubic space of the early universe, measuring about 3 million light years across, and ran it forward in time to see how galaxies would form given one of the three dark matter scenarios: cold, warm, and fuzzy.

The team began each simulation by assuming a certain distribution of dark matter, which scientists have some idea of, based on measurements of the cosmic microwave background -- "relic radiation" that was emitted by, and was detected just 400,000 years after, the Big Bang.

"Dark matter doesn't have a constant density, even at these early times," Vogelsberger says. "There are tiny perturbations on top of a constant density field."

The researchers were able to use existing algorithms to simulate galaxy formation under scenarios of cold and warm dark matter. But to simulate fuzzy dark matter, with its quantum nature, they needed a new approach.

"Dark matter doesn't have a constant density, even at these early times," Vogelsberger says. "There are tiny perturbations on top of a constant density field."

The researchers were able to use existing algorithms to simulate galaxy formation under scenarios of cold and warm dark matter. But to simulate fuzzy dark matter, with its quantum nature, they needed a new approach.