Scientists simulate dark matter in new way

Scientists have simulated dark matter in a new way, disrupting conventional thinking on the make-up of the universe.

It has been long suspected that a large proportion of the universe is made up of invisible particles,or dark matter, and that these must be very cold and heavy.

However, researchers have been led to consider alternative theories, as proof has been elusive.

The new simulations show stars and galaxies might have formed and grouped together at the origin of the universe if dark matter is very light in mass, rather than very heavy.

A University of Sussex physicist and an international team worked to calculate how dark matter would behave, and how early galaxies would have looked, if it was “fuzzy” and extremely light.

The theory hypothesises that dark matter comprises tiny particles which are so light that they behave like quantum matter, and move in waves. Their quantum nature is seen on galactic scales.

Dr Anastasia Fialkov, who conducted the research while at the University of Sussex, said: “The nature of dark matter is still a mystery.

“The fuzzy dark matter theory makes sense in terms of fundamental physics, for instance, string theory, and so is an interesting dark matter candidate.

“And if the fuzzy dark matter theory is proven right by the new generation of powerful telescopes then we will have nailed down the nature of dark matter: one of the greatest mysteries of all.

“All around the world researchers are looking for dark matter, and particle physicists are building models for dark matter, and many of them have assumed that dark matter is ‘cold’.

“The fuzzy dark matter theory, where dark matter behaves as a wave on galactic scales, now presents a credible alternative scenario – that dark matter is tiny, moves in waves behaving like quantum matter.

“Our simulations are the first ones to address galaxy formation in the context of fuzzy dark matter.”

The simulations show the shapes galaxies would have made at the beginning of the universe if dark matter was fuzzy and extremely light.

Conducted alongside Princeton, Harvard, Cambridge and MIT universities, the research contrasts them with the familiar galaxies formed in the cold dark matter scenario.

The research published in Physical Review Letters  found that if dark matter is cold, then galaxies in the early universe would have formed in nearly spherical “halos”.

But if dark matter is fuzzy, the early universe would have looked different, with galaxies forming first in extended tails, or filaments.

The shape and fragmentation of these filaments is different in each scenario.

The researcher’s aim is to provide a map for upcoming telescopes, such as the James Webb Space Telescope, that may be able to look far enough back in time to spot the earliest galaxies.

If they see galaxies with the tails, or “filaments” as simulated in this research, it may start to confirm that dark matter is fuzzy in nature.