# Testing fifth forces from the Galactic dark matter

## TL;DR

This paper investigates the possibility of a fifth force between dark matter and ordinary matter, deriving new constraints from pulsar observations that limit its strength to less than 1% of gravity.

## Contribution

It introduces a novel bound on fifth forces from pulsar data, complementing existing laboratory and satellite constraints.

## Key findings

- Fifth force strength limited to less than 1% of gravity for neutral hydrogen.
- Combines pulsar data with other bounds to tighten constraints on dark matter interactions.
- Provides a new astrophysical constraint on long-range dark matter forces.

## Abstract

Is there an unknown long-range force between dark matter (DM) and ordinary matters? When such a fifth force exists and in the case that it is ignored, the equivalence principle (EP) is violated apparently. The violation of EP was severely constrained by, for examples, the E\"ot-Wash laboratory experiments, the lunar laser ranging, the MICROSCOPE satellite, and the long-term observation of binary pulsars. We discuss a recent bound that comes from PSR J1713+0747. When it is combined with the other bounds, a compelling limit on the hypothetical fifth force is derived. For the neutral hydrogen, the strength of such a fifth force should not exceed $1\%$ of the gravity.