Comparing the Motion of Dark Matter and Standard Model Particles on Cosmological Scales
Dark matter has never been directly detected, so its modes of interaction remain unknown. This study compares the behavior of dark matter with that of standard model particles across cosmological distances, placing limits on any additional fifth force influencing their motion.
Typically, it is assumed that dark matter interacts only gravitationally with itself and standard model particles, meaning its motion follows Euler’s equation. This research tests that assumption by combining galaxy velocity measurements with gravitational potential data, represented by the Weyl potential, at redshifts z ∈ [0.3, 0.8].
The findings show that current observations are consistent with Euler’s equation. The study sets constraints on a hypothetical fifth force that could affect how dark matter falls inside gravitational wells:
- A positive fifth force may not exceed 7% of the gravitational force strength.
- A negative fifth force is limited to 21% of the gravitational force strength.
"We find that current data are consistent with Euler’s equation at redshifts z ∈ [0.3, 0.8], and we place constraints on the strength of a potential fifth force, which would alter the way dark matter particles fall."
Future surveys, such as the Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory and the Dark Energy Spectroscopic Instrument (DESI), will significantly improve these constraints, potentially limiting deviations from pure gravitational interactions to around 2%.
Author's Summary
This study confirms that dark matter’s motion aligns with gravitational predictions at cosmological scales and limits any additional forces to less than 7% positive or 21% negative compared to gravity.