Structure des hypergroupes quotients et des hypergroupes de type U

A few results are given concerning hypergroups of type C on the right, then a new class of hypergroups is defined:the hypergroups of type U on the right, which forms a more general class than the hypegroups of type C on the right; these latter can be considered as quotients of an hypergroup of type U by one of its subhypergroupe ultra-clos on the right. Then we study the structures of the quotients H/h of an hypergroup H modulo one of its subhypergroups h bi-ultra-clos or conjugable,and, in that last case, we characterize the core of H/h. At last, a requisite condition is determined so that an hypergroup quotient, H/h of an hypergroup H modulo one of its subhypergroups h, may be a commutative hypergroup. We are driven to definite the derived subhypergroup D(H) of H. We particularly analyse the structure of D(H) in the case H would be of type C on the right.