Time delays across saddles as a test of modified gravity

Abstract

Modified gravity theories can produce strong signals in the vicinity of the saddles of the total gravitational potential. In a sub-class of these models this translates into diverging time-delays for echoes crossing the saddles. Such models arise from the possibility that gravity might be infrared divergent or confined, and if suitably designed they are very difficult to rule out. We show that Lunar Laser Ranging during an eclipse could probe the time-delay effect within meters of the saddle, thereby proving or excluding these models. Very Large Baseline Interferometry, instead, could target delays across the Jupiter-Sun saddle. Such experiments would shed light on the infrared behaviour of gravity and examine the puzzling possibility that there might be well-hidden regions of strong gravity and even singularities inside the solar system.

Version published in Classical and Quantum Gravity

References in corpus (8)

• Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions
• Bimetric MOND gravity
• MOND habitats within the solar system
• General relativistic observables of the GRAIL mission
• Testing quasilinear modified Newtonian dynamics in the Solar System
• Astrodynamical Space Test of Relativity using Optical Devices I (ASTROD I) - Mission Overview
• Parameterised free functions and saddle stresses in modified gravity
• Saddle stresses for generic theories with a preferred acceleration scale

Cited by in corpus (3)

• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• A general class of gravitational theories as alternatives to dark matter where the speed of gravity always equals the speed of light
• Tests of Modified Gravity Theories in the Solar System