New supercomputer simulations suggest that dark energy, the force accelerating the universe's expansion, might be dynamic rather than constant. Led by researchers in Japan, the study aligns with observations from the Dark Energy Spectroscopic Instrument (DESI). This could reshape understanding of cosmic structure formation.
Since the early 20th century, evidence has shown the universe expanding at an accelerating rate, driven by dark energy, a mysterious property of spacetime. The standard Lambda Cold Dark Matter (ΛCDM) model assumes dark energy remains constant, but recent DESI data hints at a dynamic dark energy (DDE) component, challenging this view.
A team led by Associate Professor Tomoaki Ishiyama of Chiba University's Digital Transformation Enhancement Council in Japan, with collaborators Francisco Prada from the Instituto de Astrofísica de Andalucía in Spain and Anatoly A. Klypin from New Mexico State University in the United States, conducted extensive simulations. Published in Physical Review D (Volume 112, Issue 4), the study used Japan's Fugaku supercomputer for three high-resolution N-body simulations, each with a volume eight times larger than previous efforts.
One simulation followed the Planck-2018 ΛCDM model, while two incorporated DDE. A third used parameters from DESI's first-year data, including a 10% increase in matter density. Results showed subtle effects from DDE alone, but with adjusted matter density, the DDE model predicted 70% more massive galaxy clusters in the early universe compared to the standard model. This higher density enhances gravitational attraction, accelerating cluster formation.
The simulations also matched DESI observations in baryonic acoustic oscillations (BAOs), with the BAO peak shifting 3.71% toward smaller scales. Galaxy clustering was stronger on smaller scales in the DDE model, aligning with data.
"Our large simulations demonstrate that variations in cosmological parameters, particularly the matter density in the Universe, have a greater influence on structure formation than the DDE component alone," says Dr. Ishiyama.
These findings prepare for future surveys like the Subaru Prime Focus Spectrograph and DESI, which will refine cosmological parameters.