[1] Wroclaw Univ, Inst Theoret Phys, Pl Maxa Borna 9, PL-50205 Wroclaw, Poland
[2] Rudjer Boskovi Inst, Div Theoret Phys, Bijenicka c 54, HR-10002 Zagreb, Croatia
[3] Univ Cagliari, Dipartimento Matemat, Via Osped 72, I-09124 Cagliari, Italy
[4] INFN, Sez Cagliari, I-09042 Monserrato, Italy
[5] Univ South Eastern Norway, Dept Microsyst, Notodden, Campus Vestfold, Norway