Modified Entropic Force
  The theory of statistical thermodynamics tells us the equipartition law of
energy does not hold in the limit of very low temperatures. It is found the
Debye model is very successful in explaining the experimental results for most
of the solid objects. Motivated by this fact, we modify the entropic force
formula which is proposed very recently. Since the Unruh temperature is
proportional to the strength of gravitational field, so the modified entropic
force formula is an extension of the Newtonian gravity to weak field. On the
contrary, General Relativity extends Newtonian gravity to strong field case.
Corresponding to Debye temperature, there exists a Debye acceleration g_D. It
is found the Debye acceleration is g_D=10^{-15}N kg^{-1}. This acceleration is
very much smaller than the gravitational acceleration 10^{-4}N kg^{-1} which is
felt by the Neptune and the gravitational acceleration 10^{-10}N kg^{-1} felt
by the Sun. Therefore, the modified entropic force can be very well
approximated by the Newtonian gravity in the solar system and in the Galaxy.
With this Debye acceleration, we find the current cosmic speeding up can be
explained without invoking any kind of dark energy.
