Researchers from Chiba University (Japan), together with colleagues from Spain and the United States, conducted one of the largest cosmological simulations to test the hypothesis of "dynamic dark energy." This concept suggests that the accelerated expansion of the Universe is caused not by a constant value, but by energy that changes over time. The results of the study were published in the journal Physical Review D (PRD).

Until now, the standard ΛCDM cosmological model has treated dark energy as an unchanging quantity, making up about 68% of the total energy of the Universe. However, data from the international Dark Energy Spectroscopic Instrument (DESI) survey pointed to possible variations in its properties, prompting scientists to reconsider established theories.

Supercomputer Fugaku and Three Scenarios of Evolution

To test the hypothesis, the scientists used the power of Japan’s Fugaku supercomputer, one of the most powerful in the world. They simulated the evolution of the Universe under three scenarios:

  • The standard ΛCDM model with constant dark energy.
  • A model with dynamic dark energy, changing over time.
  • An updated model incorporating refined parameters from DESI data.

The simulations showed that the dynamics of dark energy itself had a moderate effect on the formation of cosmic structures such as galaxy clusters. However, when accounting for the higher matter density indicated by DESI, the differences became significant. In the early Universe, up to 70% more massive galaxy clusters formed than predicted by the standard model.

In addition, the researchers recorded a shift in the peak of baryon acoustic oscillations (BAO)—a key indicator related to the distribution of matter—by almost 4% toward smaller scales. This observation coincides with DESI results and aligns more closely with the real pattern of galaxy clustering in the Universe.

A Key Factor: Not Just Dark Energy

Lead researcher Tomoaki Ishiyama emphasized that the evolution of the Universe is influenced not only by changes in dark energy but also by refined cosmological parameters such as matter density. “Our models show that the structure of the Universe is sensitive to these parameters. Dynamic dark energy, combined with DESI data, gives a picture that is closer to reality,” he noted.

Outlook: New Surveys and Refined Models

Scientists expect that future observations, including the Subaru Prime Focus Spectrograph (PFS) project and the continuation of DESI, will provide more data to test the hypothesis. These surveys will help refine the parameters of dark energy and determine whether it is truly dynamic. If confirmed, this could revolutionize our understanding of the evolution of the Universe and require a revision of the ΛCDM model.

In Brief...

Scientists from Chiba University, using the Fugaku supercomputer, demonstrated that dark energy may be dynamic, changing over time. Simulations revealed that, when DESI data is taken into account, the early Universe formed 70% more galaxy clusters and the BAO peak shifted by 4%. This confirms that the structure of the Universe depends not only on dark energy but also on matter density. Upcoming surveys by Subaru PFS and DESI will help determine whether dark energy changes over time—potentially reshaping cosmology.