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: "Cooperative Spectrum Sharing in Cognitive Radio Networks: A Game-Theoretic Approach"
  Abstract: We consider the problem of cooperative spectrum sharing among a primary user (PU) and multiple secondary users (SUs), where the PU selects a proper set of secondary users to serve as the cooperative relays for its transmission. In return, the PU leases portion of channel access time to the selected SUs for their own transmission. The PU decides the portion of channel access time it will leave for the selected SUs (i.e., the cooperative relays), and the cooperative relays decide their respective power level used to help PU's transmission in order to achieve proportional access time to the channel. We assume that the PU and SUs are rational and selfish, i.e., they only aim at maximizing their own utility. As SU's utility is in term of their own transmission rate and the power cost for PU's transmission, so they will choose a proper power level to meet the tradeoff between transmission rate and power cost. PU will choose a proper portion of channel access time for the cooperative relays to attract them to employ higher power level. We formulate the problem as a non-cooperative game between PU and SUs, and prove that the proposed game converges to a unique Stackelberg equilibrium. By employing an iterative updating algorithm, we can achieve the unique equilibrium point.

Connected through hyperedge HE-1 (induced by source paper "Distributed Relay Selection and Power Control for Multiuser Cooperative Communication Networks Using Buyer/Seller Game"):
  with members:
    - "Stimulating Cooperative Diversity in Wireless Ad Hoc Networks through Pricing"
    - "Joint Relay and Jammer Selection and Power Control for physical Layer Security in Two-Way Relay Networks with Imperfect CSI"

Connected through hyperedge HE-2 (induced by source paper "Cooperative Spectrum Allocation for Cognitive Radio Network: An Evolutionary Approach"):
  with members:
    - "A Demand-Based Spectrum Allocation Algorithm in Cognitive Radio Networks"

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: Computer science