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: "abstraction of elementary hybrid systems by variable transformation"
  Abstract: Elementary hybrid systems (EHSs) are those hybrid systems (HSs) containing elementary functions such as exp, ln, sin, cos, etc. EHSs are very common in practice, especially in safety-critical domains. Due to the non-polynomial expressions which lead to undecidable arithmetic, verification of EHSs is very hard. Existing approaches based on partition of state space or over-approximation of reachable sets suffer from state explosion or inflation of numerical errors. In this paper, we propose a symbolic abstraction approach that reduces EHSs to polynomial hybrid systems (PHSs), by replacing all non-polynomial terms with newly introduced variables. Thus the verification of EHSs is reduced to the one of PHSs, enabling us to apply all the well-established verification techniques and tools for PHSs to EHSs. In this way, it is possible to avoid the limitations of many existing methods. We illustrate the abstraction approach and its application in safety verification of EHSs by several real world examples.

Connected through hyperedge HE-1 (induced by source paper "synthesizing basic semialgebraic invariants by semidefinite programming"):
  with members:
    - "horn ice learning for synthesizing invariantsand contracts"
    - "polynomial invariants for affine programs"
    - "julia a fresh approach to numerical computing"
    - "generating non linear interpolants by semidefinite programming"
    - "predicate generation for learning based quantifier free loop invariant inference"

Connected through hyperedge HE-2 (induced by source paper "differential equation invariance axiomatization"):
  with members:
    - "a heuristic prover for real inequalities"
    - "delta decidability over the reals"
    - "computing semi algebraic invariants for polynomial dynamical systems"

Connected through hyperedge HE-3 (induced by source paper "barrier certificates revisited"):
  with members:
    - "exponential condition based barrier certificate generation for safety verification of hybrid systems"
    - "generating non linear interpolants by semidefinite programming"
    - "proving inequalities and solving global optimization problems via simplified cad projection"
    - "computing semi algebraic invariants for polynomial dynamical systems"
    - "exact safety verification of hybrid systems using sums of squares representation"

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.SY(Systems and Control)