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: "tree width for first order formulae"
  Abstract: We introduce tree-width for first order formulae \phi, fotw(\phi). We show that computing fotw is fixed-parameter tractable with parameter fotw. Moreover, we show that on classes of formulae of bounded fotw, model checking is fixed parameter tractable, with parameter the length of the formula. This is done by translating a formula \phi\ with fotw(\phi)<k into a formula of the k-variable fragment L^k of first order logic. For fixed k, the question whether a given first order formula is equivalent to an L^k formula is undecidable. In contrast, the classes of first order formulae with bounded fotw are fragments of first order logic for which the equivalence is decidable. #R##N#Our notion of tree-width generalises tree-width of conjunctive queries to arbitrary formulae of first order logic by taking into account the quantifier interaction in a formula. Moreover, it is more powerful than the notion of elimination-width of quantified constraint formulae, defined by Chen and Dalmau (CSL 2005): for quantified constraint formulae, both bounded elimination-width and bounded fotw allow for model checking in polynomial time. We prove that fotw of a quantified constraint formula \phi\ is bounded by the elimination-width of \phi, and we exhibit a class of quantified constraint formulae with bounded fotw, that has unbounded elimination-width. A similar comparison holds for strict tree-width of non-recursive stratified datalog as defined by Flum, Frick, and Grohe (JACM 49, 2002). #R##N#Finally, we show that fotw has a characterization in terms of a cops and robbers game without monotonicity cost.

Connected through hyperedge HE-1 (induced by source paper "the theory of concatenation over finite models"):
  with members:
    - "dynamic complexity of document spanners"
    - "matching patterns with variables"
    - "weight annotation in information extraction"
    - "constant delay enumeration for nondeterministic document spanners"
    - "split correctness in information extraction"
    - "deterministic regular expressions with back references"
    - "constant delay algorithms for regular document spanners"
    - "the hardness of solving simple word equations"

Connected through hyperedge HE-2 (induced by source paper "faq questions asked frequently"):
  with members:
    - "size bounds and query plans for relational joins"
    - "constraint solving via fractional edge covers"
    - "what do shannon type inequalities submodular width and disjunctive datalog have to do with one another"
    - "computing join queries with functional dependencies"
    - "general and fractional hypertree decompositions hard and easy cases"
    - "join processing for graph patterns an old dog with new tricks"
    - "emptyheaded boolean algebra based graph processing"
    - "joins via geometric resolutions worst case and beyond"

Connected through hyperedge HE-3 (induced by source paper "the logic of counting query answers"):
  with members:
    - "counting answers to existential positive queries a complexity classification"
    - "the tractability frontier of graph like first order query sets"
    - "a trichotomy in the complexity of counting answers to conjunctive queries"
    - "structural tractability of counting of solutions to conjunctive queries"
    - "one hierarchy spawns another graph deconstructions and the complexity classification of conjunctive queries"
    - "on the complexity of existential positive queries"

Connected through hyperedge HE-4 (induced by source paper "the tractability frontier of graph like first order query sets"):
  with members:
    - "counting answers to existential positive queries a complexity classification"
    - "complexity of counting subgraphs only the boundedness of the vertex cover number counts"
    - "a trichotomy in the complexity of counting answers to conjunctive queries"
    - "structural tractability of counting of solutions to conjunctive queries"
    - "one hierarchy spawns another graph deconstructions and the complexity classification of conjunctive queries"
    - "the fine classification of conjunctive queries and parameterized logarithmic space complexity"
    - "on the complexity of existential positive queries"

Connected through hyperedge HE-5 (induced by source paper "on the complexity of existential positive queries"):
  with members:
    - "on the complexity of the model checking problem"
    - "tractable hypergraph properties for constraint satisfaction and conjunctive queries"
    - "the succinctness of first order logic on linear orders"

Connected through hyperedge HE-6 (induced by source paper "does treewidth help in modal satisfiability"):
  with members:
    - "a note on the complexity of the satisfiability problem for graded modal logics"
    - "parameterized modal satisfiability"
    - "generalized modal satisfiability"
    - "on the complexity of elementary modal logics"
    - "characterizing the np pspace gap in the satisfiability problem for modal logic"

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)