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Simple theory may explain mysterious dark matter, physicists say

Theoretical physicists at Vanderbilt University contend that a simply theory may explain mysterious dark matter. They propose that most of the matter in the universe may be constructed of particles that have an abnormal, donut-shaped electromagnetic field known as an anapole.

According to a news release from Vanderbilt University, Professor Robert Scherrer and post-doctoral fellow Chiu Man Ho carried out an in-depth analysis to determine the validity of this theory. Scherrer points out that he likes this theory because of “its simplicity, uniqueness and the fact that it can be tested.” notes that approximately 80 percent of all the matter in the universe is made up of dark matter. Dark matter is material that physicists cannot directly observe. Why is this? Because dark matter does not emit light or energy. Scherrer and Ho suggest that dark matter may be constructed of a type of basic particle known as the Majorana fermion. Though the particle’s existence was predicted in the 1930’s, it has doggedly resisted detection.

While this theory has been previously put forth, Scherrer and Ho have shown that these particles are uniquely adapted to have an anapole. This field gives the Majorana particles properties that vary from those of particles that have the more common fields possessing two poles and illustrates why they are so hard to detect.

According to Scherrer, a lot of models for dark matter expect that it interacts through exotic forces that we do not come across on a daily basis. However, anapole dark matter utilizes ordinary electromagnetism like the force that makes magnets stick to your refrigerator. Scherrer and Ho also point out that the model makes predictions about the rate at which anapole dark matter should reveal itself in the dark matter detectors that are hidden underground. According to these predictions, the existence of anapole dark matter will soon be proven or ruled out by these experiments.

Ever since Italian physicist Ettore Majorana created a variation of Paul Dirac’s formulation that predicts the existence of an electrically neutral fermion, physicists have been looking for Majorana fermions. Though the main candidate has been the neutrino, scientists have not yet been able to figure out the basic nature of this particle.

Scientists believe that dark matter also explains why stars far from the center of galaxies are traveling at much higher velocities than can be reasoned by the amount of visible matter that the galaxies have. Scientists believe that these galaxies contain a sizable amount of undetectable dark matter. This dark matter cannot be spotted in telescopes because it does not interface very strongly with light and other electromagnetic radiation.

However, several physicists have studied dark matter particles that don’t contain electrical charges, but possess electric or magnetic dipoles. Unfortunately, even these more complex models are ruled out for Majorana particles, which is why Ho and Scherrer performed an in-depth analysis of dark matter with an anapole magnetic moment.

According to Ho, “fundamental symmetries of nature” prevent Majorana fermions from obtaining any electromagnetic properties except the anapole.

The physicists contend that particles with anapole fields must be moving before they interact and the quicker they move the better the interaction. Therefore, anapole particles were probably a lot more interactive during the early days of the universe and would likely have become less and less interactive over time.

The anapole dark matter particles proposed by Ho and Scherrer would demolish in the early universe, and the left-over particles from the process would create the dark matter around today. Because anapole interaction relies on how fast the particles move, these particles would have evaded detection so far.

The study’s findings are described in greater detail in the journal Physics Letters B.