Testing the MOND Paradigm of Modified Dynamics with Galaxy-Galaxy
  Gravitational Lensing
  MOND predicts that the asymptotic gravitational potential of an isolated,
bounded (baryonic) mass, M, is phi(r)=(MGa0)^{1/2}ln(r); a0 is the MOND
constant. Relativistic MOND theories predict that the lensing effects of M are
dictated by phi(r) as general-relativity lensing is dictated by the Newtonian
potential. Thus, MOND predicts that the asymptotic Newtonian potential deduced
from galaxy-galaxy gravitational lensing will have: (1) a logarithmic r
dependence, and (2) a normalization (parametrized standardly as 2s^2) that
depends only on M: s=(MGa0/4)^{1/4}. I compare these predictions with recent
results of galaxy-galaxy lensing, and find agreement on all counts. For the
"blue"-lenses subsample ("spiral" galaxies) MOND reproduces the observations
well with an r'-band M/L of 1-3 solar units, and for "red" lenses ("elliptical"
galaxies) with M/L of 3-6 solar units, both consistent with baryons only. In
contradistinction, Newtonian analysis requires, typically, M/L values of about
130 solar units, bespeaking a mass discrepancy of a factor of about 40.
Compared with the staple, rotation-curve tests, MOND is here tested in a wider
population of galaxies, through a different phenomenon, using relativistic test
objects, and is probed to several-times-lower accelerations--as low as a few
percent of a0.
