This paper concerns the study of the solutions of sup-T equations such
that ATR=A, where T is a triangular norm and R is a fuzzy relation. B
y generalizing a result from Sanchez [12], we determine the greatest T
-eigen fuzzy set of a fuzzy relation (a T-eigen fuzzy set of R being a
fuzzy set A which is a solution of ATR=A). We also study some algebra
ic properties for the class of the T-eigen sets of a fuzzy relation, a
nd for the set of fuzzy relations leaving invariant a given fuzzy set.
Finally, properties related with the transitive closure are establish
ed.