  The fact that in Minkowski space, space and time are both quantized does not
have to be introduced as a new postulate in physics, but can actually be
derived by combining certain features of General Relativity and Quantum
Mechanics. This is demonstrated first in a model where particles behave as
point defects in 2 space dimensions and 1 time, and then in the real world
having 3+1 dimensions. The mechanisms in these two cases are quite different,
but the outcomes are similar: space and time form a (non-cummutative) lattice.
  These notes are short since most of the material discussed in these lectures
is based on two earlier papers by the same author (gr-qc/9601014 and
gr-qc/9607022), but the exposition given in the end is new.
