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: "on differential passivity of physical systems"
  Abstract: Differential passivity is a property that allows to check with a pointwise criterion that a system is incrementally passive, a property that is relevant to study interconnected systems in the context of regulation, synchronization, and estimation. The paper investigates how restrictive is the property, focusing on a class of open gradient systems encountered in the coenergy modeling framework of physical systems, in particular the Brayton-Moser formalism for nonlinear electrical circuits.

Connected through hyperedge HE-1 (induced by source paper "krasovskii s passivity"):
  with members:
    - "differentiation and passivity for control of brayton moser systems"
    - "differential passivity like properties for a class of nonlinear systems"
    - "a differential lyapunov framework for contraction analysis"

Connected through hyperedge HE-2 (induced by source paper "differentiation and passivity for control of brayton moser systems"):
  with members:
    - "krasovskii s passivity"
    - "robust passivity based control of boost converters in dc microgrids"
    - "transient stability guarantees for ad hoc dc microgrids"
    - "differential passivity like properties for a class of nonlinear systems"

Connected through hyperedge HE-3 (induced by source paper "differential passivity like properties for a class of nonlinear systems"):
  with members:
    - "a differential lyapunov framework for contraction analysis"

Connected through hyperedge HE-4 (induced by source paper "differential dissipativity theory for dominance analysis"):
  with members:
    - "a dissipativity theorem for p dominant systems"
    - "differential positivity on compact sets"
    - "differentially positive systems"
    - "on differentially dissipative dynamical systems"
    - "a differential lyapunov framework for contraction analysis"

Connected through hyperedge HE-5 (induced by source paper "conditions on shifted passivity of port hamiltonian systems"):
  with members:
    - "permanent magnet synchronous motors are globally asymptotically stabilizable with pi current control"
    - "new results on disturbance rejection for energy shaping controlled port hamiltonian systems"
    - "an internal model approach to optimal frequency regulation in power grids with time varying voltages"
    - "a differential lyapunov framework for contraction analysis"

Connected through hyperedge HE-6 (induced by source paper "differential analysis of nonlinear systems revisiting the pendulum example"):
  with members:
    - "differentially positive systems"
    - "on differentially dissipative dynamical systems"
    - "a differential lyapunov framework for contraction analysis"

Connected through hyperedge HE-7 (induced by source paper "a differential lyapunov framework for contraction analysis"):
  with members:
    - "on differentially dissipative dynamical systems"

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)