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: "reachability preservers new extremal bounds and approximation algorithms"
  Abstract: In this paper we prove new results about the extremal structure of paths in directed graphs. Say we are given a directed graph $G = (V, E)$ on $n$ nodes, a set of sources $S \subseteq V$ of size $|S|=n^{1/3}$, and a subset $P \subseteq S \times V$ of pairs $(s,t)$ where $s \in S$, of size $O(n^{2/3})$, such that for all pairs $(s,t) \in P$, there is a path from $s$ to $t$. Our goal is to remove as many edges from $G$ as possible while maintaining the reachability of all pairs in $P$. How many edges will we have to keep? Can you always go down to $n^{1+o(1)}$ edges? Or maybe for some nasty graphs $G$ you cannot even go below the simple bound of $O(n^{4/3})$ edges? #R##N#In this paper, we make polynomial progress in both the upper and lower bounds for these Reachability Preservers over bounds that were implicit in the literature. We show that in the above scenario, $O(n)$ edges will always be sufficient, and in general one is even guaranteed a subgraph on $O(n+\sqrt{n \cdot |P|\cdot |S|})$ edges that preserves the reachability of all pairs in $P$. We complement this with a lower bound graph construction, establishing that the above result fully characterizes the settings in which we are guaranteed a preserver of size $O(n)$. Moreover, we design an efficient algorithm that can always compute a preserver of existentially optimal size. #R##N#The second contribution of this paper is a new connection between extremal graph sparsification results and classical Steiner Network Design problems. Surprisingly, prior to this work, the osmosis of techniques between these two fields had been superficial. This allows us to improve the state of the art approximation algorithms for the most basic Steiner-type problem in directed graphs from the $O(n^{0.6+\varepsilon})$ of Chlamatac, Dinitz, Kortsarz, and Laekhanukit (SODA'17) to $O(n^{0.577+\varepsilon})$.

Connected through hyperedge HE-1 (induced by source paper "some general structure for extremal sparsification problems"):
  with members:
    - "improved guarantees for vertex sparsification in planar graphs"
    - "linear size distance preservers"
    - "additive spanners a simple construction"
    - "on pairwise spanners"

Connected through hyperedge HE-2 (induced by source paper "graph spanners a tutorial review"):
  with members:
    - "near additive spanners and near exact hopsets a unified view"
    - "some general structure for extremal sparsification problems"
    - "weighted additive spanners"
    - "near additive spanners in low polynomial deterministic congest time"
    - "multi level graph sketches via single level solvers"
    - "almost shortest paths and pram distance oracles in weighted graphs"
    - "an fpt algorithm for minimum additive spanner problem"
    - "distributed construction of light networks"

Connected through hyperedge HE-3 (induced by source paper "near isometric terminal embeddings for doubling metrics"):
  with members:
    - "a light metric spanner"
    - "prioritized metric structures and embedding"
    - "on pairwise spanners"
    - "optimal euclidean spanners really short thin and lanky"
    - "ramsey partitions and proximity data structures"
    - "fast construction of nets in low dimensional metrics and their applications"

Connected through hyperedge HE-4 (induced by source paper "improved guarantees for vertex sparsification in planar graphs"):
  with members:
    - "steiner point removal with distortion o log k"
    - "steiner point removal distant terminals don t really bother"
    - "near optimal compression for the planar graph metric"
    - "a hierarchy of lower bounds for sublinear additive spanners"
    - "linear size distance preservers"
    - "graph minors for preserving terminal distances approximately lower and upper bounds"
    - "the 4 3 additive spanner exponent is tight"
    - "routing in undirected graphs with constant congestion"

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.DS(Data Structures and Algorithms)