The research sheds light on a new model of cosmological dark matter

The research sheds light on a new model of cosmological dark matter

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The center of a dark matter fuzzy halo, labeled a “coherent solitonic nucleus” in the image above, is physically indistinguishable from a coherent BEC such as those created in typical cold atomic systems, but which span thousands of light-years. With the inclusion of a small transition region, the rest of the halo is incoherent due to a tangle of quantum vortices traversing the halo volume outside the vortex-free core. The vortex tangle is time dependent, but the overall vorticity it creates remains constant over time. Credit: Dr. Gary Liu, Newcastle University

Researchers at Newcastle University have used insights gained from Bose Einstein’s study of ultracold atomic condensates to analyze the behavior of fuzzy dark matter, a new model for cosmological dark matter that has recently attracted the attention of cosmologists.

They found that the physical state of the nucleus of dark matter fuzzy halos, the gravitationally bound structures in which galaxies like ours are thought to form, is the same as that of Bose-Einstein condensates (BECs) formed in laboratory atom traps. .

The interdisciplinary team also found that the fuzzy dark matter surrounding the halo nuclei is in a turbulent state, with eddies and fluctuations that inhibit coherence throughout the halo. These properties distinguish fuzzy dark matter from the more widely accepted model of cold dark matter in which there are no coherent features and no quantum vortex

Scientists have shown that the centers of dark matter halos in this fuzzy new model of dark matter are practically giant BECs, spanning not for millionths of meters (micrometres) as in typical cold atomic systems, but for thousands of light-years ( equivalent to tens of millions of billions of kilometers), including the centers of galaxies and presenting a characteristic property of quantum systems and BECs called coherence.

The study also describes the internal motions of the outer halos and the kinetic energy of the dark matter there, which gives rise to an intricate tangle of quantum vortices with characteristic density profiles in their cores.

Their results were published in the journal Monthly Notices of the Royal Astronomical Society.

Meeting of two disciplines

Cosmology deals with the very large scales of nature, from the realms of galaxies and galaxy clusters to the entire observable universe. Cosmologists make observations of the universe, obviously not being able to perform experiments, and the main natural force they deal with is gravity. Such observations revealed that most of the matter that makes up the cosmos is different from that that makes up humans, planets and stars, and is composed of an unknown substance called, for lack of a better word, dark matter.

Ultracold atomic physics, on the other hand, describes the behavior of clouds of atoms, such as the gases rubidium, potassium and sodium, typically at millionths of a degree above absolute zero in laboratories around the world, and examines the phenomena that reveal the quantum nature of question.

Credit: Newcastle University

The study brought together these two disciplines, led by Dr Gerasimos Rigopoulos and Professor Nick Proukakis of Newcastle University, respectively theorists of cosmology and ultracold atomic physics. The team also included researcher Dr. I-Kang (Gary) Liu who recently completed his Marie Curie Fellowship on the subject, Dr. Alex Soto and the PhD. student Milos Indjin.

Dr Rigopoulos, Senior Lecturer in Applied Mathematics, said: ‘Fuzzy dark matter has already been studied for some years by cosmologists, but our work has applied concepts from the study of BEC dynamics which has been around for much longer. Now understand that there are specific similarities to BECs, and the ultimate goal is to use this knowledge to devise ways to better test this exciting new observational model.”

“I have always had an eye on interdisciplinary approaches in physics and this was a perfect problem to approach from such an angle. Establishing a common language took some time but we could see right from the start, just as we were conceiving this project, that there were rewards to be reaped when you step out of your comfort zone and try to see things from a new perspective. I think our persistence has paid off and we’ve only scratched the surface of what such a partnership can do.”

Professor Proukakis, a professor of quantum physics and a strong believer in the universal characteristics of such forms of quantum coherence, added: ‘It’s great to see yet another plausible realization of a system that exhibits Bose-Einstein condensation – it’s amazing to see, like us are now dealing with a system so vast beyond the imagination of those who first study this phenomenon in controlled laboratory settings”.

“Although creating a potential gravitational pull that mimics in controlled laboratory environments remains challenging/unknown in three-dimensional systems, similar initially seemingly impossible challenges have eventually been encountered in such experimental systems. The mere prospect, though not highly probable, of possibility The future of creating laboratory environments that mimic some aspect of the distribution of matter in the universe is exciting in its own right.”

“Moreover, even as a theoretical playground, it’s great to have a new system to model, try out the vast experience gained from laboratory condensates, and hope for future observational tests in cosmology.”

Future research will focus on possible ways to observe such fuzzy dark matter features, thus placing this model under more detailed observational scrutiny.

The scientists are preparing a series of follow-up publications, having already completed a study showing the theoretical similarity of the equations governing the fuzzy model of dark matter to those used in the study of how the Bose-Einstein condensation develops in the laboratory when atomic gases are cooled to near absolute zero.

They are currently using insights from established theories designed to describe cold atoms to mathematically unify conventional cold dark matter and new fuzzy dark matter models, while also examining the implications and, in the long run, observational probes of those discoveries.

More information:
I-Kang Liu et al, Coherent and incoherent structures in dark matter fuzzy halos, Monthly Notices of the Royal Astronomical Society (2023). DOI: 10.1093/mnras/stad591

About the magazine:
Monthly Notices of the Royal Astronomical Society

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