Symmetries of Energy-Momentum Tensor:Some Basic Facts

It has been pointed out by Hall et al.[Gen.Rel.Gray.28（1996）299.]that matter collineations canbe defined by using three different methods.But there arises the question whether one studies matter collineations byusing L;T;=0,or L;T;=0 or L;T;=0.These alternative conditions are,of course,not generally equivalent.Thisproblem has been explored by applying these three definitions to general static spherically symmetric spacetimes.Wecompare the results with each definition.