Minimal and maximal elements in two-sided cells of Sn and Robinson-Schensted correspondence

In symmetric groups, a two-sided cell is the set of all permutations which are mapped by the Robinson-Schensted correspondence on a pair of tableaux of the same shape. In this article, we show that the set of permutations in a two-sided cell which have a minimal number of inversions is the set of permutations which have a maximal number of inversions in conjugated Young subgroups. We also give an interpretation of these sets with particular tableaux, called reading tableaux. As corollary, we give the set of elements in a two-sided cell which have a maximal number of inversions. Mathematics Subject Classification: 05E10. Author keywords: Robinson-Schensted correspondence, number of inversions, twosided cells .