The universe is expanding at an accelerating rate, like dough that keeps rising faster even though the yeast ran out long ago. For twenty years, astronomers have been searching for the cause and call it dark energy. But what it is remains a mystery.
New work proposes an unexpected source: the vacuum inside the atomic nucleus. More precisely, the vacuum of quantum chromodynamics — the theory describing how quarks stick together to form protons and neutrons. This vacuum is not empty: special clumps of fields constantly pop in and out of existence, like knots on an invisible fabric. As space expands, this "fabric" stretches, and the knots create a global tension: that very dark energy. No new particles or fields are needed.
The authors tested the model for the first time against the full set of cosmological data: cosmic microwave background from Planck, ACT, and SPT-3G, baryon acoustic oscillations from DESI, and type Ia supernovae. The model didn't just fit: it proved more convincing than the standard cosmological constant ΛCDM. Moreover, it naturally behaves like some exotic theories but without their problems. For example, at intermediate redshifts (around z~0.67), dark energy temporarily becomes "phantom"—its density grows faster than usual, but without catastrophic instability.
The expansion of the universe ceases to be a puzzle of a separate substance. Perhaps it is simply the breathing of the vacuum we already know — the very one that binds matter inside us. The dough rises not because of a secret ingredient, but because the flour itself harbors a hidden power.
as written by the authors arXiv:2606.20036
We investigate a physically motivated model of dynamical dark energy arising from the non-perturbative topological structure of the Quantum Chromodynamics (QCD) vacuum. The model introduces no new fundamental field or propagating degree of freedom: the dark energy (DE) density emerges as a global vacuum response to an expanding spacetime. We develop the first comprehensive cosmological implementation of this QCD-DE scenario and confront it with current observations, including Planck, ACT and SPT-3G cosmic microwave background data, DESI DR2 baryon acoustic oscillation measurements, and Type Ia supernova samples from Pantheon+ and DES-Dovekie. We compare the model with $$\Lambda\mathrm{CDM}$$ and $$w_0w_a\mathrm{CDM}$$ cosmologies. The model provides an excellent fit to the data and reproduces the late-time DE evolution preferred by DESI. The model naturally predicts effective phantom crossing behaviour at intermediate redshifts ($$z\sim0.67$$) while avoiding the instabilities associated with phantom scalar fields. Using goodness-of-fit statistics and Bayesian model-selection tools, including Akaike and Deviance Information Criteria and Bayesian evidence estimated from Markov-Chain Monte Carlo chains, we find that the QCD-induced model is consistently favoured over $$\Lambda\mathrm{CDM}$$ for the full combination of early and late-time datasets. Unlike the conventional descriptions of dynamical DE, support for QCD-DE in Bayesian evidence remains more consistent across datasets, suggesting that a physically motivated departure from a cosmological constant may provide a more economical description of the expansion history preferred by current observations.
The density of dark energy predicted by the model roughly matches the energy contained in the volume of a proton if "smeared" across a cubic meter of space. One proton per cubic meter, and the universe goes haywire.
In Stanisław Lem's novel "Solaris," the planet's ocean was a single thinking structure. Here, the QCD vacuum is a silent ocean whose tension governs the expansion of the cosmos.