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: "the bisimulation problem for equational graphs of finite out degree"
  Abstract: The "bisimulation problem" for equational graphs of finite out-degree is shown to be decidable. We reduce this problem to the bisimulation problem for deterministic rational (vectors of) boolean series on the alphabet of a dpda M. We then exhibit a complete formal system for deducing equivalent pairs of such vectors.

Connected through hyperedge HE-1 (induced by source paper "bisimulation equivalence of first order grammars is ackermann complete"):
  with members:
    - "equivalence of pushdown automata via first order grammars"
    - "complexity hierarchies beyond elementary"
    - "branching bisimilarity checking for prs"
    - "bisimulation equivalence of first order grammars"
    - "complexity bounds for ordinal based termination"
    - "bpa bisimilarity is exptime hard"
    - "beyond language equivalence on visibly pushdown automata"

Connected through hyperedge HE-2 (induced by source paper "bisimulation equivalence of first order grammars"):
  with members:
    - "complexity hierarchies beyond elementary"
    - "dividing line between decidable pda s and undecidable ones"
    - "branching bisimilarity checking for prs"
    - "bisimilarity on basic process algebra is in 2 exptime an explicit proof"
    - "bpa bisimilarity is exptime hard"
    - "on the complexity of the equivalence problem for probabilistic automata"

Connected through hyperedge HE-3 (induced by source paper "the complexity of the first order theory of ground tree rewrite graphs"):
  with members:
    - "algorithmic metatheorems for decidable ltl model checking over infinite systems"
    - "automatic structures of bounded degree revisited"

Connected through hyperedge HE-4 (induced by source paper "deciding semantic finiteness of pushdown processes and first order grammars w r t bisimulation equivalence"):
  with members:
    - "complexity hierarchies beyond elementary"
    - "bisimulation equivalence of first order grammars"
    - "note on undecidability of bisimilarity for second order pushdown processes"
    - "bisimilarity of pushdown systems is nonelementary"

Connected through hyperedge HE-5 (induced by source paper "bisimilarity on basic process algebra is in 2 exptime an explicit proof"):
  with members:
    - "bisimilarity of pushdown systems is nonelementary"
    - "bpa bisimilarity is exptime hard"
    - "beyond language equivalence on visibly pushdown automata"

Connected through hyperedge HE-6 (induced by source paper "bisimulation equivalence of first order grammars is ackermann hard"):
  with members:
    - "complexity hierarchies beyond elementary"

Connected through hyperedge HE-7 (induced by source paper "bpa bisimilarity is exptime hard"):
  with members:
    - "bisimilarity on basic process algebra is in 2 exptime an explicit proof"
    - "beyond language equivalence on visibly pushdown automata"
    - "decidability of higher order matching"
    - "model checking probabilistic timed automata with one or two clocks"
    - "equivalence checking on infinite state systems techniques and results"

Connected through hyperedge HE-8 (induced by source paper "bisimilarity of probabilistic pushdown automata"):
  with members:
    - "bisimilarity on basic process algebra is in 2 exptime an explicit proof"
    - "bpa bisimilarity is exptime hard"
    - "beyond language equivalence on visibly pushdown automata"

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.LO(Logic in Computer Science)