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Headlines Published on 27 April 2007

Title European researchers get closer to dark energy and dark matter

While the metaphysical study of the origin and nature of the universe has attracted scientists the world over, the question "What is the energy content of the universe?" has puzzled them for many years. Cosmologists have since made two promising discoveries: dark matter and dark energy. But difficulties still remain. Jean-Michel Alimi and André Füzfa, researchers at the Observatory of Paris in France and the Fonds de la Recherche Scientifique of Belgium, have come up with an answer: the Abnormally Weighting Energy (AWE) Hypothesis.

Dark matter © Matt+
Dark matter
Introduced by Einstein so as to incorporate Mach's principle within general relativity, the AWE Hypothesis assumes that all kinds of energies generate and experience the same form of gravity. Comprised of protons and neutrons, ordinary matter makes up only 4% of the overall energy content of the universe. Dark matter and dark energy make up the rest. Dark matter is required to elucidate the angular fluctuations of the cosmic microwave background, and the formation and properties of galaxies, while dark energy has been used to justify the noted acceleration of the cosmic expansion. Despite these explanations, however, scientists are still baffled.

Alimi and Füzfa tested the AWE Hypothesis at local scales with solid results, but what would the outcome be if the equivalence principle was rigorously verified where dark matter and dark energy exist in a small amount, but is violated on cosmological scales where dark matter and dark energy are dominant?

The two researchers, who demonstrated that the gravitational strength is contingent on dark matter concentration at a given scale, said this could happen if some particles, such as dark matter-related ones, do not couple to gravitation as ordinary matter does. Gravitational fields with a gravitational strength that varies from ordinary matter would emerge.

While the amount and amplitude of dark matter at sub-galactic scales are insignificant, the opposite is true for cosmological scales where dark matter dominates the energy content of the universe. In their research, Alimi and Füzfa found that ordinary matter is subjected to a stronger cosmic expansion over such cosmic distances. This is due to the fact that its own gravitational coupling strength has been shifting to the dark matter domination, they said.

Adaptations in the matter gravitational coupling trigger a faster cosmic expansion until equilibrium is reached. Ultimately, the gravitational coupling on cosmological scales steadies at a value unlike the one measured in the solar system.

Alimi and Füzfa said the resulting dark energy mechanism revealed four promising key features: 1) the existence of negative pressures are not needed; 2) the cosmic coincidence due to the stabilisation mechanism of the gravitational constant during the matter-dominated era can be explained naturally; 3) it accounts for the Hubble diagramme of type Ia supernovae by predicting independently the amount of ordinary matter and dark matter as obtained by the analysis of cosmic microwave background anisotropies; and 4) in future, this mechanism initiates a decelerated cosmic expansion described by the Einstein-de Sitter cosmological model.

The researchers remarked that the AWE Hypothesis allows for lessening dark energy as a new property of gravitation: the anomalous gravity of dark matter.

More information:

  • Observatory of Paris
  • Fonds de la Recherche Scientifique
  • "And then there was light"

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