Dark Energy Isn't Constant? ⚡ экспресс
The unresolved problem of constructing stable de Sitter vacua in string theory casts doubt on the observational viability of the ΛCDM model (cold dark matter with a cosmological constant). This difficulty suggests that the standard cosmological model with unchanging dark energy may reside in the "swampland"—the realm of inconsistent quantum gravity theories—rather than in the viable "landscape." Recent observational data, especially from the Dark Energy Spectroscopic Instrument (DESI), have seriously challenged ΛCDM cosmology. Joint analysis of DESI's baryon acoustic oscillation measurements with results from other surveys shows a preference for dynamical, time-evolving dark energy, whose density has decreased by roughly 10% over the last few billion years. This review summarizes key advances of the last two years in aligning DESI data with scenarios motivated by string theory.
For a long time, dark energy—the mysterious force prodding the expansion of the Universe—was considered eternal and unchanging, like yeast that never loses its activity. But explaining such constancy through the laws of the microcosm proved impossible, and scientists began to suspect that the “leaven” might be going flat.
The DESI instrument—a light analyzer of millions of distant galaxies—showed that over the past few billion years, dark energy’s strength has weakened by about 10%. By studying galaxy distributions, astronomers were surprised to find that they are not scattered randomly but arranged in concentric rings—like ripples on water from a thrown stone. This is the frozen echo of sound waves that shook the early Universe.
Now the entire recipe of the cosmic loaf is in question, where dark matter and dark energy were considered immutable ingredients. Cosmologists are trying out new recipes where the dough of space is kneaded with string-like filaments, and dark energy—like live yeast—behaves capriciously: sometimes raging, sometimes quieting down, promising a dramatic finale to the expansion.
🎯 By some estimates, dark energy makes up about 68% of all the energy in the Universe.