“…There are a number of Z-graded Gorenstein rings R such that the stable categories CM Z 0 R admit tilting objects, see e.g. [AIR,DL1,DL2,FU,G1,G2,HIMO,IO,IT,JKS,KST1,KST2,Ki1,Ki2,KLM,LP,LZ,MU,U1,U2,Ya] and a survey article [I]. Therefore the following problem is of our central interest.…”