human: Given a node-centered hypergraph: <hypergraph>, where nodes represent authors and hyperedges represent groups of authors who co-authored the same paper.

Details of the hypergraph:
Center node: "Transformations affines agissant sur un simplexe"
  Abstract: Dans ce travail nous montrons l'equivalence entre le polytope de transport symetrique T(@l) (un objet ''physique''), le polytope de Revesz P(@l) (un object ''algebrique'') et le polytope A(x"0) des transformations affines agissant sur un simplexe en laissant x"0 fixe (un objet ''geometrique'') et nous utilisons ce fait pour determiner certaines proprietes des elements extremaux de A(x"0). Une description du contenu de cet article est donnee a la Section 2.

Connected through hyperedge HE-1 (induced by source paper "Polytopes de transport symetriques"):
  with members:
    (none)

Question: Please tell me which research area the center author belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Mathematics