[Paper Review] Testing MOND/TEVES with LISA Pathfinder

C. Trenkel, Steve Kemble+2 more|arXiv (Cornell University)|Jan 8, 2010

Geophysics and Gravity Measurements4 citations

TL;DR

This paper proposes using the LISA Pathfinder mission to test the TeVeS (Tensor-Vector-Scalar) theory of Modified Newtonian Dynamics (MOND) by flying through the Sun-Earth Lagrange L1 saddle point to detect anomalous gravity gradients predicted by MOND. If the mission's gradiometer achieves nominal performance, it could detect and characterize these signals; a null result would strongly challenge TeVeS/MOND.

ABSTRACT

We suggest that LISA Pathfinder could be used to subject TEVES, and in particular the non-relativistic MOND phenomenology it incorporates, to a direct, controlled experimental test, in just a few years' time. The basic concept is to fly LISA Pathfinder through the region around the Sun-Earth saddle point, following its nominal mission, in order to look for anomalous gravity gradients. We examine various strategies to reach the saddle point, and conclude that the preferred strategy, resulting in relatively short transfer times of order one year, probably involves a lunar fly-by. We present robust estimates of the MOND gravity gradients that LISA Pathfinder should be exposed to, and conclude that if the gradiometer on-board the spacecraft achieves its nominal performance, these gradients will not just be detected, but measured and characterised in some detail, should they exist. Conversely, given the large predicted signal based on standard assumptions, a null result would most likely spell the end of TEVES/MOND.

Motivation & Objective

• To propose a direct, controlled test of the TeVeS theory of Modified Newtonian Dynamics (MOND) using the LISA Pathfinder mission.
• To evaluate feasible trajectories for reaching the Sun-Earth L1 saddle point within ~1 year, including lunar fly-by strategies.
• To estimate the magnitude of MONDian gravity gradients expected at the L1 point under standard assumptions.
• To assess whether LISA Pathfinder’s gradiometer can detect and characterize these anomalies if they exist.
• To determine the implications of a null result for the viability of TeVeS and MOND.

Proposed method

• Model the gravitational potential and gradients in the vicinity of the Sun-Earth L1 point using Newtonian and MONDian dynamics.
• Use orbital mechanics to simulate transfer trajectories to the L1 point, evaluating fuel efficiency and duration.
• Incorporate the lunar fly-by maneuver as a preferred strategy to reduce transfer time to approximately one year.
• Calculate the expected MONDian gravity gradient signal based on the non-relativistic MOND phenomenology embedded in TeVeS.
• Assess the sensitivity of the LISA Pathfinder gradiometer to detect such signals, assuming nominal performance.
• Compare predicted MOND signals with expected instrumental noise levels to determine detectability.

Experimental results

Research questions

• RQ1 Can LISA Pathfinder detect MOND-induced gravity gradients at the Sun-Earth L1 point?
• RQ2 What is the optimal trajectory for reaching the L1 point within one year, including lunar fly-by considerations?
• RQ3 How strong are the MOND gravity gradients expected at the L1 point under standard TeVeS assumptions?
• RQ4 To what extent can the LISA Pathfinder gradiometer resolve and characterize a potential MOND signal?
• RQ5 What would a null detection imply for the validity of the TeVeS/MOND framework?

Key findings

• The MOND gravity gradient signal at the Sun-Earth L1 point is predicted to be large enough to be detectable by LISA Pathfinder’s gradiometer if the instrument achieves its nominal performance.
• A lunar fly-by trajectory offers a feasible path to reach the L1 point in approximately one year, minimizing transfer time.
• The predicted MOND signal is robust under standard assumptions, making it a strong candidate for detection.
• If the signal is not detected despite nominal instrument performance, this would constitute a strong disproof of the TeVeS/MOND framework.
• The mission could not only detect the signal but also characterize its spatial and directional features in detail.
• The study establishes LISA Pathfinder as a viable platform for a direct, controlled test of MOND/TeVeS within a few years.