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: "S-T connectivity on digraphs with a known stationary distribution"
  Abstract: We present a deterministic logspace algorithm for solving S-T Connectivity on directed graphs if: (i) we are given a stationary distribution of the random walk on the graph in which both of the input vertices  s  and  t  have nonnegligible probability mass and (ii) the random walk which starts at the source vertex  s  has polynomial mixing time. This result generalizes the recent deterministic logspace algorithm for S-T Connectivity on undirected graphs [Reingold, 2008]. It identifies knowledge of the stationary distribution as the gap between the S-T Connectivity problems we know how to solve in logspace ( L ) and those that capture all of randomized logspace ( RL ).

Connected through hyperedge HE-1 (induced by source paper "Pseudorandomness for Width 2 Branching Programs"):
  with members:
    (none)

Connected through hyperedge HE-2 (induced by source paper "In search of an easy witness: exponential time vs. probabilistic polynomial time"):
  with members:
    - "Derandomizing Arthur-Merlin Games under Uniform Assumptions"
    - "On the randomness complexity of efficient sampling"

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