A direct test of the validity of Euler’s equation for dark matter at cosmological scales has been performed by combining measurements of galaxy peculiar velocities with measurements of the Weyl potential. The results show that current data are consistent with Euler’s equation, but place constraints on the strength of a possible fifth force acting on dark matter.
Simplified content:
Dark matter particles have never been directly detected, so we don’t know how they move. We assume that dark matter only interacts gravitationally with itself and standard model particles. However, this assumption has been tested at cosmological scales by combining galaxy velocities with measurements of gravitational potential wells. The results show that current data are consistent with Euler’s equation, which describes the motion of galaxies.
The researchers used galaxy surveys and weak lensing surveys to constrain the strength of a possible fifth force acting on dark matter. They found that the amplitude of the fifth force is constrained within -21% and 7% of the gravitational interaction strength. Future data from surveys like DESI and LSST will improve the precision of these constraints.
The researchers tested several models, including those with and without a fifth force. They used numerical simulations to study how the fifth force affects the growth of structure in the universe. The results show that the fifth force can affect the growth rate of galaxies, but the effect is small compared to the gravitational interaction.
Overall, this study provides new insights into the nature of dark matter and its possible interactions with the standard model of particle physics. The researchers hope that future surveys will provide more precise measurements of the strength of any possible fifth force acting on dark matter.
Keywords: dark matter, Euler’s equation, fifth force, galaxy velocities, gravitational potential wells, cosmological scales, DESI, LSST
Source: https://www.nature.com/articles/s41467-025-65100-8