Combined Solar System and rotation curve constraints on MOND

TL;DR

This paper investigates how the External Field Effect in MOND influences galactic rotation curves and Solar System constraints, ruling out some transition functions and assessing future observational prospects.

Contribution

It demonstrates the impact of the External Field Effect on galactic and Solar System dynamics, constrains MOND transition functions using Cassini data, and evaluates LISA Pathfinder's potential.

Findings

External Field Effect improves galactic rotation curve fits.

Cassini data constrains MOND transition functions.

LISA Pathfinder cannot significantly improve current constraints.

Abstract

The Modified Newtonian Dynamics (MOND) paradigm generically predicts that the external gravitational field in which a system is embedded can produce effects on its internal dynamics. In this communication, we first show that this External Field Effect can significantly improve some galactic rotation curves fits by decreasing the predicted velocities of the external part of the rotation curves. In modified gravity versions of MOND, this External Field Effect also appears in the Solar System and leads to a very good way to constrain the transition function of the theory. A combined analysis of the galactic rotation curves and Solar System constraints (provided by the Cassini spacecraft) rules out several classes of popular MOND transition functions, but leaves others viable. Moreover, we show that LISA Pathfinder will not be able to improve the current constraints on these still viable transition functions.