Gauge CPT as a Possible Alternative to the Dark Matter Hypothesis
  A new force is proposed in order to explain galactic rotation curves. CPT is
chosen as the underlying symmetry of the new force because it is a universal
spacetime symmetry. Local CPT transformations are presented for the Dirac field
(matter) and the vierbein describing curved spacetime. A nonvanishing variation
of the Dirac action in curved spacetime is thus derived. Because the metric
spin connection of general relativity cannot accommodate the variation induced
by the local CPT symmetry, a new gauge field is introduced. The transformation
of the new field is derived which implies the new field is massless.
Experimental speculations based on the zero mass of the new gauge field are
presented. It is shown that one type of Yang-Mills Lagrangian density is not
invariant under local CPT transformations.
