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: "a 1 5 approximation for path tsp"
  Abstract: We present a $1.5$-approximation for the Metric Path Traveling Salesman Problem (Path TSP). All recent improvements on Path TSP crucially exploit a structural property shown by An, Kleinberg, and Shmoys [Journal of the ACM, 2015], namely that narrow cuts with respect to a Held-Karp solution form a chain. We significantly deviate from these approaches by showing the benefit of dealing with larger $s$-$t$ cuts, even though they are much less structured. More precisely, we show that a variation of the dynamic programming idea recently introduced by Traub and Vygen [SODA, 2018] is versatile enough to deal with larger size cuts, by exploiting a seminal result of Karger on the number of near-minimum cuts. This avoids a recursive application of dynamic programming as used by Traub and Vygen, and leads to a considerably simpler algorithm avoiding an additional error term in the approximation guarantee. We match the still unbeaten $1.5$-approximation guarantee of Christofides' algorithm for TSP. Hence, any further progress on the approximability of Path TSP will also lead to an improvement for TSP.

Connected through hyperedge HE-1 (induced by source paper "minimum scan cover with angular transition costs"):
  with members:
    - "covering tours and cycle covers with turn costs hardness and approximation"
    - "bounded angle spanning tree modeling networks with angular constraints"
    - "optimal covering tours with turn costs"

Connected through hyperedge HE-2 (induced by source paper "reducing path tsp to tsp"):
  with members:
    - "beating the integrality ratio for s t tours in graphs"
    - "better s t tours by gao trees"
    - "reassembling trees for the traveling salesman"
    - "eight fifth approximation for the path tsp"
    - "new inapproximability bounds for tsp"
    - "approximating minimum cost connected t joins"
    - "improving christofides algorithm for the s t path tsp"
    - "13 9 approximation for graphic tsp"

Connected through hyperedge HE-3 (induced by source paper "beating the integrality ratio for s t tours in graphs"):
  with members:
    - "an improved upper bound on the integrality ratio for the s t path tsp"
    - "a constant factor approximation algorithm for the asymmetric traveling salesman problem"
    - "approaching frac 3 2 for the s t path tsp"
    - "approximation hardness of graphic tsp on cubic graphs"
    - "improving christofides algorithm for the s t path tsp"

Connected through hyperedge HE-4 (induced by source paper "an improved upper bound on the integrality ratio for the s t path tsp"):
  with members:
    - "layers and matroids for the traveling salesman s paths"
    - "better s t tours by gao trees"
    - "reassembling trees for the traveling salesman"
    - "eight fifth approximation for the path tsp"
    - "improving christofides algorithm for the s t path tsp"

Connected through hyperedge HE-5 (induced by source paper "approaching frac 3 2 for the s t path tsp"):
  with members:
    - "an improved upper bound on the integrality ratio for the s t path tsp"
    - "layers and matroids for the traveling salesman s paths"
    - "better s t tours by gao trees"
    - "reassembling trees for the traveling salesman"
    - "improving christofides algorithm for the s t path tsp"

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.DM(Discrete Mathematics)