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Physicists report a way to 'hear' dark matter
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"Physicists at Stockholm University and the Max Planck Institute for Physics have turned to plasmas in a proposal that could revolutionise the search for the elusive dark matter.
Dark matter makes up 85 percent of the matter in the universe. Originally introduced to explain why the strong force, which holds together protons and neutrons, is the same backwards and forwards in time, the so-called axion would provide a natural explanation for dark matter. Rather than discrete particles, axion dark matter would form a pervasive wave flowing throughout space.
The axion is one of the best explanations for dark matter, but has only recently been the focus of large-scale experimental effort. Now, there is a rush to come up with new ideas to find the axion in all the areas where it could be hiding.
"Finding the axion is a bit like tuning a radio: You have to tune your antenna until you pick up the right frequency. Rather than music, experimentalists would be rewarded with 'hearing' the dark matter that the Earth is traveling through. Despite being well motivated, axions have been experimentally neglected during the three decades since they were named by coauthor Frank Wilczek," says Dr. Alexander Millar at the Department of Physics, Stockholm University, and author of the study.
The key insight of the research team's new study is that inside a magnetic field, axions would generate a small electric field that could be used to drive oscillations in the plasma. In a plasma, charged particles such as electrons can flow freely as a fluid. These oscillations amplify the signal, leading to a better "axion radio." Unlike traditional experiments based on resonant cavities, there is almost no limit on how large these plasmas can be, thus providing a larger signal. The difference is somewhat like the difference between a walkie talkie and a radio broadcast tower."
[link to m.phys.org (secure)]
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