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The density of dark matter in an expanding universe decreases more quickly than dark energy, and eventually the dark energy dominates. Specifically, when the volume of the universe doubles, the density of dark matter is halved, but the density of dark energy is nearly unchanged (it is exactly constant in the case of a cosmological constant).
The researchers used a year of observations by the Dark Energy Spectroscopic Instrument (DESI) at Kitt Peak National Observatory in Arizona, which can capture light from 5,000 galaxies simultaneously.
In these models, the quintessence field has a density which closely tracks (but is less than) the radiation density until matter-radiation equality, which triggers quintessence to start having characteristics similar to dark energy, eventually dominating the universe. This naturally sets the low scale of the dark energy. [12]
Different theories of dark energy suggest different values of w, with w < − 1 / 3 for cosmic acceleration (this leads to a positive value of ä in the acceleration equation above). The simplest explanation for dark energy is that it is a cosmological constant or vacuum energy; in this case w = −1.
Since the 1990s, studies have shown that, assuming the cosmological principle, around 68% of the mass–energy density of the universe can be attributed to dark energy. [6] [7] [8] The cosmological constant Λ is the simplest possible explanation for dark energy, and is used in the standard model of cosmology known as the ΛCDM model.
Dark energy – Energy driving the accelerated expansion of the universe; Dark matter – Concept in cosmology; Gravitational interaction of antimatter – Theory of gravity on antimatter; Mirror matter – Hypothetical counterpart to ordinary matter; Negative energy – Concept in physics; Negative mass – Concept in physical models
The fraction of the total energy density of our (flat or almost flat) universe that is dark energy, , is estimated to be 0.669 ± 0.038 based on the 2018 Dark Energy Survey results using Type Ia supernovae [7] or 0.6847 ± 0.0073 based on the 2018 release of Planck satellite data, or more than 68.3% (2018 estimate) of the mass–energy density ...
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