Based on the usual mannequin of cosmology, that enlargement price must be the identical irrespective of the way you measure it. However lately, scientists have discovered that the enlargement price of the early universe and that of the more moderen universe differ by roughly 9 %.
That discrepancy, or rigidity, “has provoked heated debates within the cosmology group about whether or not this distinction could possibly be as a result of systematic errors or whether or not it’s a sign of latest physics,” Teixeira and her co-authors wrote. Their mannequin posits that in a world the place darkish power and darkish matter work together, what appeared to be a disaster brought on by disparate enlargement charges as a substitute turns into one thing to be anticipated.
A Darkish Dimension
If darkish power and darkish matter do work together, it may imply that they’ve a standard origin, Khoury stated.
Ongoing work in string concept—the concept our universe, at its smallest, most basic degree, is made up of vibrating strings—suggests a approach these ideas is likely to be related. In 2019, constructing on the concept in string concept that darkish power is naturally various, Vafa and two collaborators concluded that the mass of darkish matter particles may additionally differ over time. This led them to suggest in 2022 that darkish matter and darkish power may share a hyperlink with a so-called darkish dimension.
String concept posits the existence of six or seven further dimensions along with our acquainted three dimensions of area and one among time. All of those dimensions are regarded as as small as bodily attainable—near the Planck scale (10-35 meters)—however the researchers proposed that the darkish dimension could possibly be considerably larger than the others—on the order of a micron (10-6 meters).
Gravitons, theoretical particles that impart the power of gravity, may leak into this enlarged darkish dimension. In the event that they did, they might choose up mass and turn out to be what are known as darkish gravitons. These large gravitons would reside at midnight dimension, however their gravitational results could possibly be felt in different dimensions, permitting them to meet the function that’s usually ascribed to darkish matter.
On this situation, “there’s a very pure coupling between darkish power and darkish matter,” stated Georges Obied, a physicist on the College of Chicago. Modifications within the measurement of the darkish dimension would have an effect on each darkish power and darkish matter.
In a July 2025 paper, Obied and Vafa, together with Alek Bedroya of Princeton and David Wu of Harvard, discovered that the situation proposed in 2019 was in keeping with the DESI knowledge. Their mannequin predicts that the energy of darkish power and the mass of darkish matter will lower over time and that the speed at which darkish power adjustments can be proportional to its power density. As a result of astrophysical measurements inform us that the power density of darkish power is awfully small, “it received’t change quick,” Vafa stated.
“It’s not stunning that we didn’t see it till now,” he stated, as a result of the speed of change is so tiny. “We needed to wait your complete age of the universe to detect one thing that small.”
