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: "fragments of first order logic over infinite words"
  Abstract: We give topological and algebraic characterizations as well as language theoretic descriptions of the following subclasses of first-order logic FO[<] for omega-languages: Sigma_2, FO^2, the intersection of FO^2 and Sigma_2, and Delta_2 (and by duality Pi_2 and the intersection of FO^2 and Pi_2). These descriptions extend the respective results for finite words. In particular, we relate the above fragments to language classes of certain (unambiguous) polynomials. An immediate consequence is the decidability of the membership problem of these classes, but this was shown before by Wilke and Bojanczyk and is therefore not our main focus. The paper is about the interplay of algebraic, topological, and language theoretic properties.

Connected through hyperedge HE-1 (induced by source paper "well quasiorders and hierarchy theory"):
  with members:
    - "on the state complexity of closures and interiors of regular languages with subwords and superwords"
    - "decidability in the logic of subsequences and supersequences"
    - "generalized post embedding problems"
    - "the height of piecewise testable languages with applications in logical complexity"

Connected through hyperedge HE-2 (induced by source paper "quantifier alternation for infinite words"):
  with members:
    - "separating regular languages with two quantifier alternations"
    - "separating regular languages with first order logic"
    - "level two of the quantifier alternation hierarchy over infinite words"
    - "going higher in the first order quantifier alternation hierarchy on words"
    - "separating regular languages by piecewise testable and unambiguous languages"
    - "efficient separability of regular languages by subsequences and suffixes"

Connected through hyperedge HE-3 (induced by source paper "level two of the quantifier alternation hierarchy over infinite words"):
  with members:
    - "quantifier alternation for infinite words"
    - "going higher in the first order quantifier alternation hierarchy on words"
    - "one quantifier alternation in first order logic with modular predicates"
    - "first order fragments with successor over infinite words"

Connected through hyperedge HE-4 (induced by source paper "languages of dot depth one over infinite words"):
  with members:
    - "first order fragments with successor over infinite words"
    - "logic meets algebra the case of regular languages"
    - "algebraic characterization of logically defined tree languages"
    - "algebraic recognizability of languages"

Connected through hyperedge HE-5 (induced by source paper "regular ideal languages and their boolean combinations"):
  with members:
    - "around dot depth one"
    - "rankers over infinite words"

Connected through hyperedge HE-6 (induced by source paper "rankers over infinite words"):
  with members:
    - "representations of stream processors using nested fixed points"
    - "structure theorem and strict alternation hierarchy for fo2 on words"

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.FL(Formal Languages and Automata Theory)