For each of the stellar, galactic, and galaxy cluster/super cluster observations the basic principle is that if we measure velocities in some region, then there has to be enough mass there for gravity to stop all the objects flying apart. When such velocity measurements are done on large scales, it turns out that the amount of inferred mass is much more than can be explained by the luminous stuff. Hence we infer that there is dark matter in the Universe. Dark matter (DM) candidates are usually split into two broad categories, Baryonic and Non-Baryonic with the second category being further sub-divided into (HDM) hot dark matter and cold dark matter (CDM) depending on their respective masses and speeds. CDM candidates travel at slow speeds (hence "cold") or have little pressure, while HDM candidates move rapidly (hence "hot").
Astrophysical observations increasingly suggest there's a large amount of cold dark matter in the universe, and the axion, a hypothetical elementary particle, is a compelling dark-matter candidate. Dark-matter axions normally have only feeble couplings to matter and radiation, but a RF cavity threaded by a magnetic field causes a few nearby halo axions to convert into microwave photons. These photons can then be detected with an exquisitely sensitive receiver, and several groups around the world search in this way for Milky Way halo axions at the upper end of their expected coupling range.
The research group at Lawrence Livermore National Laboratory launched a high-sensitivity upgrade that exploits advances in low-noise quantum electronics. These upgraded receivers are by far the world's most sensitive to microwave radiation, having noise near the quantum limit. This upgraded experiment will be definitive, capable of detecting or ruling out the entire range of plausible dark-matter axion masses and couplings.
Summary of talk by Leslie Rosenberg at the University of Washington science colloquium.
Astrophysical observations increasingly suggest there's a large amount of cold dark matter in the universe, and the axion, a hypothetical elementary particle, is a compelling dark-matter candidate. Dark-matter axions normally have only feeble couplings to matter and radiation, but a RF cavity threaded by a magnetic field causes a few nearby halo axions to convert into microwave photons. These photons can then be detected with an exquisitely sensitive receiver, and several groups around the world search in this way for Milky Way halo axions at the upper end of their expected coupling range.
The research group at Lawrence Livermore National Laboratory launched a high-sensitivity upgrade that exploits advances in low-noise quantum electronics. These upgraded receivers are by far the world's most sensitive to microwave radiation, having noise near the quantum limit. This upgraded experiment will be definitive, capable of detecting or ruling out the entire range of plausible dark-matter axion masses and couplings.
Summary of talk by Leslie Rosenberg at the University of Washington science colloquium.
No comments:
Post a Comment