Hello everybodyI need to introduce a dipolar interaction in  my one dimensional sustem.How can I do this....?Best regardsHocine  ------------------------------------------------------------------------- Mr Hocine Ahmed LABORATORY FOR THEORETICAL PHYSICS AND MATERIAL PHYSICS HASSIBA BENBOUALI UNIVERSITY BP. 151, 02000 CHLEF, ALGERIA Tel:+213790974582 ;  mail: ah.hocine@univ-chlef.dz