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: "the frobenius and factor universality problems of the free monoid on a finite set of words"
  Abstract: We settle complexity questions of two problems about the free monoid $L^*$ generated by a finite set $L$ of words over an alphabet $\Sigma$. The first one is the \emph{Frobenius monoid problem}, which is whether for a given finite set of words $L$, the language $L^*$ is cofinite. The open question concerning its computational complexity was originally posed by Shallit and Xu in~2009. The second problem is whether $L^*$ is \emph{factor universal}, which means that every word over $\Sigma$ is a factor of some word from $L^*$. It is related to the longstanding Restivo's open question from~1981 about the maximal length of the shortest words which are not factors of any word from $L^*$. We show that both problems are PSPACE-complete, which holds even if the alphabet is binary. Additionally, we exhibit families of sets $L$ that show exponential (in the sum of the lengths of words in $L$ or in the length of the longest words in $L$) worst-case lower bounds on the lengths related to both problems: the length of the longest words not in $L^*$ when $L^*$ is cofinite, and the length of the shortest words that are not a factor of any word in $L^*$ when $L^*$ is not factor universal. The second family essentially settles in the negative the Restivo's conjecture and its weaker variations. As auxiliary tools, we introduce the concept of \emph{set rewriting systems}. Finally, we note upper bounds on the computation time and the length for both problems, which are exponential only in the length of the longest words in $L$.

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)