New theoretical work suggests that dark energy and dark matter, the two dominant yet invisible components of the cosmos, may be physically intertwined rather than separate entities. Recent observational data indicates that dark energy is not constant but evolves over time, a finding that has reignited interest in models where dark matter influences dark energy.
In 2024, the Dark Energy Spectroscopic Instrument (DESI) collaboration reported evidence that the strength of dark energy, traditionally considered a fixed cosmological constant, appears to have weakened after peaking roughly two billion years ago. Subsequent analyses reinforced the idea that dark energy changes, potentially entering a “phantom regime” where its behavior seems to defy standard energy conservation laws.
Physicists such as Cumrun Vafa of Harvard University argue that this apparent anomaly arises from assuming dark energy and dark matter are independent. “The notion that you can compute dark energy independently of dark matter is wrong,” Vafa said, noting that the phantom behavior is likely an artifact of incorrect bookkeeping regarding dark matter mass variations.
This perspective is supported by earlier theoretical frameworks. In 2005, Justin Khoury of the University of Pennsylvania demonstrated that interacting dark sectors could produce phantom-like effects. More recently, researchers including Elsa Teixeira of the University of Montpellier have proposed models where dark matter transfers energy to dark energy, offering a potential resolution to the Hubble tension—a discrepancy of about 9 percent between measurements of the universe’s expansion rate from different cosmic eras.
A compelling explanation emerges from string theory, which posits the existence of a “dark dimension.” Proposed by Vafa and colleagues, this hypothesis suggests dark matter and dark energy share a common origin linked to an extra spatial dimension larger than the Planck scale but microscopic in human terms. In this model, gravitons leak into the dark dimension, acquiring mass and acting as dark matter, while changes in the dimension’s size affect both dark energy and dark matter simultaneously.
Recent calculations by Vafa, Georges Obied, and collaborators show their model is consistent with DESI data, predicting that both dark energy density and dark matter mass decrease over time at rates proportional to the tiny energy density of dark energy. Although direct detection remains challenging, astronomers have existing observational bounds from galaxy interaction studies that allow for the predicted strength of new forces between dark matter particles.
Wait, so dark matter is just massive gravitons? And the phantom regime is just bad accounting? Fascinating—if true, it solves so many headaches at once.
This string theory angle is brilliant. If gravitons leak into a hidden dimension, it neatly explains why dark matter and energy seem linked.