Physicist proposes new way to look for the elusive stuff

Dec 10, 2013 09:28 GMT  ·  By
A rendering of how a halo of dark matter might look like inside a galaxy cluster
   A rendering of how a halo of dark matter might look like inside a galaxy cluster

The search for dark matter may have already been successful, argues theoretical physicist Christian Beck, who is based at the Queen Mary University of London. The expert says that the elusive stuff, believed to account for about a quarter of the Universe's mass-energy budget, may have been discovered as far back as 2004. 

Finding dark matter is one of the most important goals in astrophysics today. The stuff is believed to lie at the cores of galaxies, and to exist in large clumps at the center of galaxy clusters. For example, both Milky Way and Andromeda are believed to be heading towards the core of the Virgo Supercluster on a dark matter filament.

This elusive form of matter is believed to account for more than 85 percent of all matter in the Universe. However, theories suggest that it interacts weakly with regular, baryonic matter, and that its effects are mostly felt through gravitational interactions, Space reports.

Given its unwillingness to interact with regular particles, dark matter is nearly impossible to detect, yet numerous detectors have been constructed over the years. Thus far, none of these instruments has been able to detect conclusive evidences to support the existence of dark matter.

These detectors hope to identify rare instances when dark matter particles interact with baryonic matter particles. These collisions are hypothesized to produce specific signatures that can potentially be seen. Beck suggests that benchtop detectors may be more useful for this search than larger, buried ones.

He argues that smaller instruments would be better able to detect axions, which are hypothetical elementary particles believed to be a possible component of cold dark matter. Their existence was first postulated in 1977 by the Peccei–Quinn theory, but their existence was never confirmed.

Recent investigations suggest that axions are capable of coming together to form the so-called Bose-Einstein condensate, a state of matter consisting of a dilute boson gas cooled close to absolute zero.

“I started thinking not about the behavior of single axions, but [about] the collective behavior of many axions coupled together,” Beck says. In his work, the physicist found that the equations describing the behavior of axions were similar to those describing the S/N/S Josephson junction, a type of circuit.

If this were true, then axions passing through S/N/S Josephson junctions would leave behind a detectable signal, meaning that an entirely new way of searching for dark matter could be developed. Furthermore, it is possible that such signals may have already been discovered.

A signal of unknown origin was detected in a study of S/N/S Josephson junctions, conducted in 2004. Experimenters at the time sought to analyze noise levels inside these circuits, and came across a signal that Beck says might have been produced by axions. Further studies are needed to confirm this idea.