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: "alternating towers and piecewise testable separators"
  Abstract: Two languages are separable by a piecewise testable language if and only if there exists no infinite tower between them. An infinite tower is an infinite sequence of strings alternati ng between the two languages such that every string is a subsequence (scattered substring) of all the strings that f ollow. For regular languages represented by nondeterministic finite automata, the existence of an infinite tower is decidab le in polynomial time. In this paper, we investigate the complexity of a particular method to compute a piecewise testable separator. We show that it is closely related to the height of maximal finite towers, and provide the upper and lower bounds with respect to the size of the given nondeterministic automata. Specifically, we show that the u pper bound is polynomial with respect to the number of states with the cardinality of the alphabet in the exponen t. Concerning the lower bound, we show that towers of exponential height with respect to the cardinality of the alphabet exist. Since these towers mostly turn out to be sequences of prefixes, we also provide a comparison with towe rs of prefixes.

Connected through hyperedge HE-1 (induced by source paper "testing simon s congruence"):
  with members:
    - "on the index of simon s congruence for piecewise testability"
    - "structure theorem and strict alternation hierarchy for fo2 on words"

Connected through hyperedge HE-2 (induced by source paper "on the height of towers of subsequences and prefixes"):
  with members:
    - "separability by piecewise testable languages is ptime complete"
    - "on the index of simon s congruence for piecewise testability"
    - "on upper and lower bounds on the length of alternating towers"
    - "a characterization for decidable separability by piecewise testable languages"
    - "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 "on the state complexity of closures and interiors of regular languages with subwords and superwords"):
  with members:
    - "decidability in the logic of subsequences and supersequences"
    - "refinement and difference for probabilistic automata"
    - "finite automata for the sub and superword closure of cfls descriptional and computational complexity"
    - "the power of priority channel systems"
    - "computing downward closures for stacked counter automata"
    - "quotient complexity of ideal languages"
    - "decision problems for convex languages"
    - "the computational complexity of universality problems for prefixes suffixes factors and subwords of regular languages"

Connected through hyperedge HE-4 (induced by source paper "piecewise testable languages and nondeterministic automata"):
  with members:
    - "on the index of simon s congruence for piecewise testability"
    - "on upper and lower bounds on the length of alternating towers"
    - "separating regular languages by piecewise testable and unambiguous languages"
    - "efficient separability of regular languages by subsequences and suffixes"
    - "piecewise testable tree languages"
    - "around dot depth one"

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)