Dark Energy Isn't Constant? ⚡ экспресс
Attempts to construct stable de Sitter vacua (necessary for describing the accelerating universe) in string theory encounter difficulties. This casts doubt on the standard ΛCDM model with constant dark energy: perhaps it falls into the "swampland" (the marsh of inconsistent quantum gravity theories) rather than the "landscape" of viable models. New data from the DESI telescope on baryon acoustic oscillations (imprints of sound waves from the early universe) indicate that dark energy is not constant: its density has decreased by about 10% over the last few billion years. This review summarizes the progress of the last two years in incorporating DESI results into scenarios inspired 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.