An experiment to test popular dark energy theory finds no evidence of new forces, placing strong constraints on related theories.
Dark energy is the name given to an unknown force that causes the universe to expand at an accelerating rate.
Some physicists have suggested that dark energy is the "fifth" force acting on matter beyond the four already known ̵
However, researchers believe that this fifth force can be "screened" or "hidden" for large objects such as planets or gravities on Earth, making it difficult to detect them.
Now, researchers at Imperial College London and the University of Nottingham have tested the possibility that this fifth force acts on single atoms and found no evidence of this in their last experiment.
This may exclude popular dark energy theories that change the theory of gravity and there are fewer places to look for the elusive fifth force. Finding the Fifth Force
The experiment, conducted at Imperial College London and analyzed by theorists at the University of Nottingham, was reported in Physical Review Letters3.
Professor Ed Copeland of the Center for Astronomy and Particle Physics at the University of Nottingham says: "This experiment, linking atomic physics and cosmology, has allowed us to exclude a wide range of models that have been proposed to explain the nature of dark energy. and will allow us to limit many more dark energy models.
Dark energy theories were tested in the experiment, which suggested that the fifth force was comparatively weaker when there was more matter around – the opposite of how gravity behaves.
This would mean that it is strong in a vacuum-like space but weak when there is a lot of matter around. Therefore, experiments using two high weights would mean that the force becomes too weak to measure.
Experiment with a single atom
Researchers instead test more weight with an incredibly low weight – one atom – where strength should be observed, if any .
The team uses an atomic interferometer to check if there are additional forces that could be the fifth force acting on an atom. A marble-sized metal sphere was placed in a vacuum chamber and atoms were allowed to fall inside the chamber.
The theory is that if there is a fifth force acting between the sphere and the atom, the path of the atom will deviate slightly as it passes the sphere, causing a change in the path of the falling atom. However, no such force was found.
Professor Ed Hinds, of the Department of Physics at Imperial, says: "It is very exciting to be able to discover something about the evolution of the universe using a mass experiment in a London basement. "
Reference:" An experiment for the detection of forces of dark energy using atomic interferometry "by DA Sabulski, I. Duta, EA Hinds, B. Elder, K. Buryage and Edmund J. Copeland, 6 August 2019, Physical Examination Letters . Doi: 10.1103 / PhysRevLett.123.061102