  Using the Finite Difference Time Domain method, we solve Maxwell's equations
numerically and compute the distribution of electromagnetic fields and forces
inside material media. The media are generally specified by their dielectric
permittivity epsilon(w) and magnetic permeability mu(w), representing small,
transparent dielectric and magnetic objects such as platelets and micro-beads.
Using two formulations of the electromagnetic force-density, one due to H. A.
Lorentz [Collected Papers 2, 164 (1892)], the other due to A. Einstein and J.
Laub [Ann, Phys. 331, 541 (1908)], we show that the force-density distribution
inside a given object can differ substantially between the two formulations.
This is remarkable, considering that the total force experienced by the object
is always the same, irrespective of whether the Lorentz or the Einstein-Laub
formula is employed. The differences between the two formulations should be
accessible to measurement in deformable objects.
