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: "deciding definability in fo2 h v on trees"
  Abstract: We provide a decidable characterization of regular forest languages definable#N#in FO2(<h,<v). By FO2(<h,<v) we refer to the two variable fragment of first#N#order logic built from the descendant relation and the following sibling#N#relation. In terms of expressive power it corresponds to a fragment of the#N#navigational core of XPath that contains modalities for going up to some#N#ancestor, down to some descendant, left to some preceding sibling, and right to#N#some following sibling. We also show that our techniques can be applied to#N#other two variable first-order logics having exactly the same vertical#N#modalities as FO2(<h,<v) but having different horizontal modalities.

Connected through hyperedge HE-1 (induced by source paper "separating regular languages by piecewise testable and unambiguous languages"):
  with members:
    - "the separation problem for regular languages by piecewise testable languages"
    - "efficient separability of regular languages by subsequences and suffixes"

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)