In accordance with the usual mannequin of cosmology, that growth charge ought to be the identical regardless of the way you measure it. However lately, scientists have discovered that the growth charge of the early universe and that of the newer universe range by roughly 9 p.c.
That discrepancy, or stress, “has provoked heated debates within the cosmology group about whether or not this distinction may very well be because 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 gave the impression to be a disaster attributable to disparate growth charges as a substitute turns into one thing to be anticipated.
A Darkish Dimension
If darkish power and darkish matter do work together, it might imply that they’ve a typical origin, Khoury mentioned.
Ongoing work in string theory—the concept our universe, at its smallest, most elementary degree, is made up of vibrating strings—suggests a method these ideas could be linked. In 2019, constructing on the concept in string principle that darkish power is naturally varying, Vafa and two collaborators concluded that the mass of darkish matter particles may range over time. This led them to suggest in 2022 that darkish matter and darkish power might share a hyperlink with a so-called darkish dimension.
String principle posits the existence of six or seven further dimensions along with our acquainted three dimensions of area and certainly one of time. All of those dimensions are considered as small as bodily attainable—near the Planck scale (10-35 meters)—however the researchers proposed that the darkish dimension may very well be considerably larger than the others—on the order of a micron (10-6 meters).
Gravitons, theoretical particles that impart the power of gravity, might leak into this enlarged darkish dimension. In the event that they did, they’d decide up mass and turn into what are referred to as darkish gravitons. These large gravitons would reside in the dead of night dimension, however their gravitational results may very well be felt in different dimensions, permitting them to satisfy the position that’s usually ascribed to darkish matter.
On this situation, “there’s a very pure coupling between darkish power and darkish matter,” mentioned Georges Obied, a physicist on the College of Chicago. Adjustments 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 per the DESI information. 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 modifications 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 mentioned.
“It’s not shocking that we didn’t see it till now,” he mentioned, as a result of the speed of change is so tiny. “We needed to wait your entire age of the universe to detect one thing that small.”
