New analysis of data collected over three years by the Dark Energy Spectroscopy (DESI) collaboration provides strong evidence that dark energy evolves in unexpected ways.
It was long considered a “cosmological constant,” but now dark energy appears to have evolved over time. This is controversial in previous datasets.
Dr. Mustafa Ishak Bouzaki, professor of physics at the University of Texas at Dallas, is co-chair of the DESI Working Group, which interprets cosmological research data collected through international cooperation, including over 900 researchers from over 70 institutions around the world.
In April 2024, at a conference of the American Physics Association, Ishak Bouzaki presented the collaboration by presenting an analysis of the first year of data.
Is dark energy weaker over time?
New DESI data analysis, combined with other measurements, contributes to the attachment of indications that the effects of dark energy may weaken over time.
This means that the standard model of how the universe works must be updated.
These other measurements include how light left from the dawn of space (or the background of cosmic microwaves, or CMB), exploded stars (supernovaes), and light from distant galaxies are distorted by gravity (weak gravity lenses).
The importance of new discoveries in the scientific community
Researchers said so far, the preference for evolving dark energy has not yet increased to the statistical significance of 5 Sigma, the gold standard in physics that represents a threshold for discovery.
However, different combinations of DESI data mixed with CMB, supernova and weak lens measurements set the range from 2.8 sigma to 4.2 sigma.
“I think we’re reaching the point of no return because of the importance of 4.2 sigma,” Ishak Bouzaki said.
“This new analysis not only confirms previous findings that dark energy is likely to evolve over time, but also increases its importance. The most exciting part is that the evidence comes from different data sets.
“I’ve been working on the issue of space acceleration for 25 years, and my perspective is that if the evidence continues to grow and if it’s likely to do so, this will be a big thing for cosmology and all physics.”
Andrei Cuceu, a postdoctoral researcher at Berkeley Lab and co-chair of Desi’s Lyman-Alpha working group, added:
“It’s interesting and gives us more confidence to see a lot of different evidence heading in the same direction.”
The role of digital in advance of astrophysics’ quest
Desi is one of the most extensive research into the universe ever conducted. The cutting-edge instruments can simultaneously capture light from 5,000 galaxies.
The experiment is now in its fourth year of researching the sky, and aims to measure around 50 million galaxies and quasars by the time the project is finished.
Digi tracks the effects of dark energy by studying how matter spreads throughout the universe. Very early cosmic events left subtle patterns in the way matter was distributed. This is a function called Barion Acoustic Vibration (BAO).
Its Bao pattern acts as a standard ruler, and its size is directly influenced by how the universe is expanding at different times. Measuring rulers at different distances has shown the strength of dark energy throughout history by researchers.
The new analysis uses data from observations over the first three years of nearly 15 million galaxies and quasars.
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