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: "optimal placement delivery arrays"
  Abstract: In wireless networks, coded caching scheme is an effective technique to reduce network congestion during peak traffic times. A $(K,F,Z,S)$ placement delivery array ($(K,F,Z,S)$PDA in short) can be used to design a coded caching scheme with the delivery rate $S/F$ during the peak traffic times. Clearly in order to minimize delivery rate, we only need to consider a $(K,F,Z,S)$PDA with minimum $S$. For the fixed parameters $K$, $F$ and $Z$, a $(K,F,Z,S)$PDA with the minimum $S$ is called optimal. So it is meaningful to study optimal PDAs. #R##N#There are some known PDAs constructed by combinatorial design theory, hypergraphs and so on. However there is only one class of optimal PDAs (IEEE Trans. Inf. Theory 60:2856-2867, 2014) constructed by Ali and Niesen. We will focus on constructing optimal PDAs. In this paper, two classes of lower bounds on the value of $S$ in a $(K,F,Z,S)$PDA are derived first. Then two classes of recursive constructions are proposed. Consequently (i) optimal PDAs with $Z=1$ and $F-1$ for any positive integers $K$ and $F$ are obtained; (ii) several infinite classes of optimal PDAs for some $K$, $F$ and $Z$ are constructed. Finally more existence of optimal PDAs with $Z=F-2$ are given.

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.IT(Information Theory)