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: "Selfish unsplittable flows"
  Abstract: What is the price of anarchy when unsplittable demands are routed selfishly in general networks with load-dependent edge delays? Motivated by this question we generalize the model of Koutsoupias and Papadimitriou (Worst-case equilibria, in: Proc. of the 16th Annual Symp. on Theoretical Aspects of Computer Science (STACS '99), Lecture Notes in Computer Science, Vol. 1563, Springer, Berlin, 1999, pp. 404-413) to the case of weighted congestion games. We show that varying demands of users crucially affect the nature of these games, which are no longer isomorphic to exact potential games, even for very simple instances. Indeed we construct examples where even a single-commodity (weighted) network congestion game may have no pure Nash equilibrium.On the other hand, we prove that any weighted network congestion game with linear edge delays admits a pure Nash equilibrium that can be found in pseudo-polynomial time. Finally, we consider the family of l-layered networks and give a surprising answer to the question above: the price of anarchy of any weighted congestion game in a l-layered network with m edges and edge delays equal to the loads is Θ(log m/log log m).

Connected through hyperedge HE-1 (induced by source paper "A New Model for Selfish Routing"):
  with members:
    (none)

Connected through hyperedge HE-2 (induced by source paper "On the Complexity of Pure-Strategy Nash Equilibria in Congestion and Local-Effect Games"):
  with members:
    - "NP-hardness of pure Nash equilibrium in Scheduling and Network Design Games"

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