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: "separation for dot depth two"
  Abstract: The dot-depth hierarchy of Brzozowski and Cohen classifies the star-free languages of finite words. By a theorem of McNaughton and Papert, these are also the first-order definable languages. The dot-depth rose to prominence following the work of Thomas, who proved an exact correspondence with the quantifier alternation hierarchy of first-order logic: each level in the dot-depth hierarchy consists of all languages that can be defined with a prescribed number of quantifier blocks. One of the most famous open problems in automata theory is to settle whether the membership problem is decidable for each level: is it possible to decide whether an input regular language belongs to this level? #R##N#Despite a significant research effort, membership by itself has only been solved for low levels. A recent breakthrough was achieved by replacing membership with a more general problem: separation. Given two input languages, one has to decide whether there exists a third language in the investigated level containing the first language and disjoint from the second. The motivation is that: (1) while more difficult, separation is more rewarding (2) it provides a more convenient framework (3) all recent membership algorithms are reductions to separation for lower levels. #R##N#We present a separation algorithm for dot-depth two. While this is our most prominent application, our result is more general. We consider a family of hierarchies that includes the dot-depth: concatenation hierarchies. They are built via a generic construction process. One first chooses an initial class, the basis, which is the lowest level in the hierarchy. Further levels are built by applying generic operations. Our main theorem states that for any concatenation hierarchy whose basis is finite, separation is decidable for level one. In the special case of the dot-depth, this can be lifted to level two using previously known results.

Connected through hyperedge HE-1 (induced by source paper "regular separability and intersection emptiness are independent problems"):
  with members:
    - "the covering problem"
    - "regular separability of one counter automata"
    - "separating regular languages with first order logic"
    - "regular separability of parikh automata"
    - "separability of reachability sets of vector addition systems"
    - "unboundedness and downward closures of higher order pushdown automata"
    - "an approach to computing downward closures"
    - "a characterization for decidable separability by piecewise testable languages"

Connected through hyperedge HE-2 (induced by source paper "on all things star free"):
  with members:
    - "separation and covering for group based concatenation hierarchies"
    - "the covering problem"
    - "generic results for concatenation hierarchies"
    - "separating regular languages with first order logic"
    - "characterizing classes of regular languages using prefix codes of bounded synchronization delay"
    - "going higher in the first order quantifier alternation hierarchy on words"

Connected through hyperedge HE-3 (induced by source paper "separation and covering for group based concatenation hierarchies"):
  with members:
    - "the covering problem"
    - "generic results for concatenation hierarchies"
    - "going higher in the first order quantifier alternation hierarchy on words"
    - "one quantifier alternation in first order logic with modular predicates"

Connected through hyperedge HE-4 (induced by source paper "covering and separation for logical fragments with modular predicates"):
  with members:
    - "the covering problem"
    - "adding successor a transfer theorem for separation and covering"
    - "separating regular languages with first order logic"
    - "adding modular predicates to first order fragments"
    - "going higher in the first order quantifier alternation hierarchy on words"
    - "one quantifier alternation in first order logic with modular predicates"
    - "separating regular languages by piecewise testable and unambiguous languages"
    - "efficient separability of regular languages by subsequences and suffixes"

Connected through hyperedge HE-5 (induced by source paper "generic results for concatenation hierarchies"):
  with members:
    - "the covering problem"
    - "separating regular languages with two quantifier alternations"
    - "adding successor a transfer theorem for separation and covering"
    - "star height via games"
    - "going higher in first order quantifier alternation hierarchies on words"
    - "going higher in the first order quantifier alternation hierarchy 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)