Test of Einstein's Equivalence Principle by Galactic Dark Matter

TL;DR

This study tests Einstein's Equivalence Principle using a torsion balance over 115 days, finding no violation within experimental bounds and setting new, tighter limits on dark matter's influence.

Contribution

First experimental test of Einstein's Equivalence Principle considering Galactic dark matter using a long-period torsion balance.

Findings

No detectable violation of equivalence principle within bounds

Set new upper limit on dark matter-induced forces

Improved constraints on the E"otv"os parameter for dark matter

Abstract

We report here the results of operation of a torsion balance with a period of $\sim 1.27 \times 10^4$ s. The analysis of data collected over a period of $\sim$115 days shows that the difference in the accelerations towards the Galactic Center of test bodies made of aluminum and quartz was $(0.61 \pm 1.27) \times 10^{-15} \, \mathrm{ m \, s}^{-2}$. This sets a bound on the violation of the equivalence principle by forces exerted by Galactic dark matter which is expressed by the E\"otv\"os parameter $\eta_{DM} = (1.32 \pm 2.68) \times 10^{-5}$, a significant improvement upon earlier bounds.