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: "an approach to computing downward closures"
  Abstract: The downward closure of a word language is the set of all (not necessarily contiguous) subwords of its members. It is well-known that the downward closure of any language is regular. While the downward closure appears to be a powerful abstraction, algorithms for computing a finite automaton for the downward closure of a given language have been established only for few language classes. #R##N#This work presents a simple general method for computing downward closures. For language classes that are closed under rational transductions, it is shown that the computation of downward closures can be reduced to checking a certain unboundedness property. #R##N#This result is used to prove that downward closures are computable for (i) every language class with effectively semilinear Parikh images that are closed under rational transductions, (ii) matrix languages, and (iii) indexed languages (equivalently, languages accepted by higher-order pushdown automata of order 2).

Connected through hyperedge HE-1 (induced by source paper "reachability in vector addition systems is primitive recursive in fixed dimension"):
  with members:
    - "the reachability problem for petri nets is not elementary"
    - "vass reachability in three steps"
    - "unboundedness problems for languages of vector addition systems"
    - "on the upward downward closures of petri nets"
    - "the complexity of downward closure comparisons"
    - "complexity hierarchies beyond elementary"
    - "reachability in two dimensional unary vector addition systems with states is nl complete"
    - "demystifying reachability in vector addition systems"

Connected through hyperedge HE-2 (induced by source paper "intersection types for unboundedness problems"):
  with members:
    - "intersection types and counting"
    - "pumping lemma for higher order languages"
    - "the diagonal problem for higher order recursion schemes is decidable"
    - "on word and frontier languages of unsafe higher order grammars"
    - "relational semantics of linear logic and higher order model checking"
    - "ordered tree pushdown systems"
    - "finitary semantics of linear logic and higher order model checking"
    - "regular cost functions part i logic and algebra over words"

Connected through hyperedge HE-3 (induced by source paper "regular separability and intersection emptiness are independent problems"):
  with members:
    - "separation for dot depth two"
    - "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"
    - "a characterization for decidable separability by piecewise testable languages"

Connected through hyperedge HE-4 (induced by source paper "recursion schemes the mso logic and the u quantifier"):
  with members:
    - "the diagonal problem for higher order recursion schemes is decidable"
    - "unboundedness and downward closures of higher order pushdown automata"
    - "ordered tree pushdown systems"
    - "using models to model check recursive schemes"
    - "weak mso u with path quantifiers over infinite trees"
    - "io vs oi in higher order recursion schemes"
    - "weak mso with the unbounding quantifier"

Connected through hyperedge HE-5 (induced by source paper "on the upward downward closures of petri nets"):
  with members:
    - "complexity of regular abstractions of one counter languages"
    - "unboundedness and downward closures of higher order pushdown automata"
    - "a characterization for decidable separability by piecewise testable languages"
    - "finite automata for the sub and superword closure of cfls descriptional and computational complexity"
    - "computing downward closures for stacked counter automata"
    - "on selective unboundedness of vass"

Connected through hyperedge HE-6 (induced by source paper "the diagonal problem for higher order recursion schemes is decidable"):
  with members:
    - "on word and frontier languages of unsafe higher order grammars"
    - "unboundedness and downward closures of higher order pushdown automata"
    - "ordered tree pushdown systems"
    - "using models to model check recursive schemes"
    - "a characterization for decidable separability by piecewise testable languages"
    - "finite automata for the sub and superword closure of cfls descriptional and computational complexity"
    - "computing downward closures for stacked counter automata"
    - "complexity of model checking recursion schemes for fragments of the modal mu calculus"

Connected through hyperedge HE-7 (induced by source paper "on finite index indexed grammars and their restrictions"):
  with members:
    - "on the density of context free and counter languages"

Connected through hyperedge HE-8 (induced by source paper "demystifying reachability in vector addition systems"):
  with members:
    - "reasoning about data repetitions with counter systems"
    - "complexity hierarchies beyond elementary"
    - "reachability in two dimensional vector addition systems with states is pspace complete"
    - "complexity bounds for ordinal based termination"
    - "the reachability problem for vector addition systems with a stack is not elementary"
    - "algorithmic verification of asynchronous programs"
    - "ackermannian and primitive recursive bounds with dickson s lemma"
    - "on selective unboundedness of vass"

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)