Dark Monopolies: Theoretical Physicists Propose a New Candidate for Dark Matter | Physics

Professor John Terning and Dr Christopher Verhaaren of the University of California, Davis have a new candidate for dark matter – a dark monopoly – and a possible way to detect it.

Nobody knows what dark matter is, but this invisible form of matter makes up about a quarter of the Universe. Image credit: NASA Goddard Space Flight Center.

Black matter is the mysterious substance that makes up about a quarter of the Universe.

Physicists suspect that dark matter is made up of invisible particles that neither reflect nor absorb light, but are capable of exerting gravity.

All over the world, experiments are trying to detect and study these particles. Leading candidates include WIMP (weakly interacting massive particles) and axons.

“We still don’t know what dark matter is. For a long time the main candidate was the WIMP, but that seems to be almost completely ruled out,” Prof Terning said.

An alternative to the WIMP model of dark matter calls it a form of ‘dark electromagnetism‘ including ‘dark photons’ and other particles. Dark photons would have a weak coupling with “regular” photons.

Professor Terning and Dr Verhaaren add a twist to this idea: a dark magnetic monopole that would interact with the dark photon.

In the macroscopic world, magnets always have two poles, north and south. A monopole is a particle that acts like one end of a magnet.

“Black monopoles would interact with black photons and black electrons in the same way that theory predicts that electrons and photons interact with monopoles. And that involves a way to detect these dark particles,” they said.

In 1931, English theoretical physicist Paul Dirac predicted that an electron moving in a circle near a monopole would pick up a phase change in its wave function.

Since electrons exist as both particles and waves in quantum theory, the same electron could pass either side of the monopole and therefore be slightly out of phase on the other side.

This interference pattern, called the Aharonov–Bohm effectmeans that an electron passing around a magnetic field is influenced by it, even if it does not pass through the field itself.

“We could detect a black monopole because of the way it shifts the phase of electrons as they pass,” the scientists said.

“Theoretically, dark matter particles pass through us all the time. To be detectable in our model, the monopoles would have to be excited by the Sun. Then they would take about a month to reach Earth, traveling at about a thousandth the speed of light,” Professor Terning said.

The teams paper was published on the arXiv.org website.

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John Terning and Christopher B. Verhaaren. 2019. Detection of dark matter with Aharonov-Bohm. arXiv:1906.00014

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