Karma Chameleon | by Brian Koberlein



21 February 2015

An artist’s conception dark energy.
NASA / Jet Propulsion Laboratory
An artist’s conception darkish vitality.

Whereas the seek for darkish matter particles typically hits the information, there are additionally efforts underway to detect darkish vitality particles. As with darkish matter, the experiments to this point have largely decided what darkish matter isn’t moderately than what it’s.

There are two primary methods to account for darkish vitality. One is called the cosmological fixed. On this mannequin, darkish vitality is an inherent side of the construction of area and time. Thus, all through the universe there’s a fixed, uniform enlargement of spacetime that offers the impact of darkish vitality. This mannequin is the best method to account for darkish vitality, because it’s only a matter of including a time period to the standard normal relativity equations. It additionally agrees with observations thus far. However merely including a time period to your equations looks as if a little bit of a tweak mannequin. Common relativity doesn’t require a cosmological fixed, it simply permits for one. There’s no motive why there ought to be such a relentless apart from the truth that it suits remark. So numerous options have been proposed.

The most well-liked sort of other is to suggest some sort of scalar area. The thought is that the universe can be crammed with a scalar area that leads to darkish vitality. Which will appear much more loopy than a cosmological fixed, however the Higgs boson is a results of a scalar Higgs area launched to account for particle mass, and we’ve really detected it. There are a number of variations of the scalar area concept, however most of them can’t be examined utilizing present knowledge. However one model generally known as chameleon fields has simply been examined, and failed the take a look at.

The basic experiment.
Paul Hamilton, et al
The essential experiment.

The chameleon area is a “fifth pressure” area that interacts with itself to produces the consequences of darkish vitality in deep area, but additionally will get inhibited by the presence of mass. On this means you get cosmic enlargement between galaxies, however you don’t see its impact in galaxies (or in our photo voltaic system). Because the presence of mass makes it “hidden,” it acts as a type of cosmic chameleon, therefore the title. Usually I wouldn’t put a lot credence in a “simply so” mannequin like this, however a number of months in the past it was demonstrated that the mannequin might really be examined. Due to its chameleon impact, the sector might be “trapped” inside a vacuum cavity. By making the matter within the chamber as little as attainable, the chameleon area would strengthen within the chamber. Consequently, the efficient gravitational pressure throughout the vacuum is altered. Utilizing an atom interferometer (mainly a double-slit experiment utilizing atoms as a substitute of electrons) the change in gravity might be measured. What the workforce discovered was that there was no measured impact to the boundaries of their experiment.

This mainly guidelines out the chameleon area and comparable fashions. There’s nonetheless a number of methods the mannequin might be tweaked to nonetheless exist throughout the limits of this experiment, nevertheless it doesn’t look good for chameleon fields. That’s not significantly stunning, since most proposed fashions shall be incorrect. What makes this fascinating is that we’re now really testing darkish vitality fashions within the lab.

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