1. MOND (Modified Newtonian dynamics) habitats inside the Solar system
João Magueijo
Perimeter Institute,
CITA,
Imperial College
Based on Bekenstein & Magueijo, astro-ph/

2. The MOND vs Dark Matter conflict
Everything outside the Solar system refuses to follow the laws of General Relativity/ Newtonian gravity
Either gravity is fine, but there is an extra source we can’t see: the dark matter.
Or the observations are telling us to modify gravity.

3. We need a direct detection!
Dark matter searches: the game is over if a dark matter particle is detected!
What is the equivalent “backyard” detection of MONDian behavior?

4. (Spiral) Galaxy rotation curves:
Flattening of rotation curves
Anomalous behaviour triggered by
Tully-Fisher relation

5. Take these facts as “Kepler’s laws” for a new theory of gravity
Milgrom’s insight:
A better formulation:
(often quoted as a rule of thumb)

6. What the Solar system needs from MOND:
A modified Poisson equation
(there are several relativistic, Lagrangian formulations leading to this)

8. Why a direct test? Both approaches have been in turn un/successful
LeVerrier prediction of Neptune from Uranus orbital anomalies (first example of dark matter).
Attemps to explain the anomalous precession of the perihelion of Mercury with “Vulcanus”

9. A backyard detection of MOND?
Lagrange points?
Saddle points.

10. Naïve expectation:
MONDian tidal stresses should diverge at the saddle:
Newtonian result:
Take the squareroot:

12. Outside (perturbative) region
Maximal fractional effect is at the border ellipsoid
Its value is
It then falls off as 1/r^2

13. The inner region profile
The angular profile is approximately Newtonian
The tidal stress divergence is there but it’s much softer due to the curl term

14. LISA Pathfinder mission
LISA PAthfinder to be launched October 2009.
Lagrange L1 is 1% of way to the Sun. The MOND point is 0.1%
Two free proof masses. Can measure relative accelerations in MOND ballpark.
Timothy Sumner, Blackett Lab in Imperial College.
Deep MOND region 10 m across; but because of chaotic motions in teh SS we cannot predict the location of the critical point that accurately.

15. A target for LPF? Accelerometers have a sensitivity of
Target region for Sun/Earth saddle has size

16. CONCLUSIONS
Don’t accuse us of not providing you with a target
Most of other approaches are too fudged to make concrete predictions at this level
If you don’t like the model (I don’t) the solution is simple:
KILL IT!