human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "approximability of the six vertex model"
  Abstract: In this paper we take the first step toward a classification of the approximation complexity of the six-vertex model, an object of extensive research in statistical physics. Our complexity results conform to the phase transition phenomenon from physics. We show that the approximation complexity of the six-vertex model behaves dramatically differently on the two sides separated by the phase transition threshold. Furthermore, we present structural properties of the six-vertex model on planar graphs for parameter settings that have known relations to the Tutte polynomial $T(G, x, y)$.

Connected through hyperedge HE-1 (induced by source paper "zeros and approximations of holant polynomials on the complex plane"):
  with members:
    - "fast algorithms at low temperatures via markov chains"
    - "counting perfect matchings and the eight vertex model"
    - "counting independent sets and colorings on random regular bipartite graphs"
    - "algorithms for bis hard problems on expander graphs"
    - "zeros of holant problems locations and algorithms"
    - "the complexity of approximating the matching polynomial in the complex plane"
    - "algorithmic pirogov sinai theory"
    - "the ising partition function zeros and deterministic approximation"

Connected through hyperedge HE-2 (induced by source paper "slow mixing of glauber dynamics for the six vertex model in the ferroelectric and antiferroelectric phases"):
  with members:
    - "random tilings with the gpu"
    - "nearly tight bounds for sandpile transience on the grid"
    - "canonical paths for mcmc from art to science"
    - "approximating holant problems by winding"

Connected through hyperedge HE-3 (induced by source paper "counting perfect matchings and the eight vertex model"):
  with members:
    - "functional clones and expressibility of partition functions"
    - "approximating holant problems by winding"
    - "inapproximability of the tutte polynomial"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.CC(Computational Complexity)