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 simple proof of the existence of a planar separator"
  Abstract: We provide a simple proof of the existence of a planar separator by showing that it is an easy consequence of the circle packing theorem. We also reprove other results on separators, including: #R##N#(A) There is a simple cycle separator if the planar graph is triangulated. Furthermore, if each face has at most $d$ edges on its boundary, then there is a cycle separator of size O(sqrt{d n}). #R##N#(B) For a set of n balls in R^d, that are k-ply, there is a separator, in the intersection graph of the balls, of size O(k^{1/d}n^{1-1/d}). #R##N#(C) The k nearest neighbor graph of a set of n points in R^d contains a separator of size O(k^{1/d} n^{1-1/d}). #R##N#The new proofs are (arguably) significantly simpler than previous proofs.

Connected through hyperedge HE-1 (induced by source paper "computing circle packing representations of planar graphs"):
  with members:
    - "matrix scaling and balancing via box constrained newton s method and interior point methods"
    - "strongly monotone drawings of planar graphs"
    - "approximate gaussian elimination for laplacians fast sparse and simple"
    - "sparsified cholesky and multigrid solvers for connection laplacians"
    - "the galois complexity of graph drawing why numerical solutions are ubiquitous for force directed spectral and circle packing drawings"
    - "balanced circle packings for planar graphs"
    - "an efficient parallel solver for sdd linear systems"
    - "efficient accelerated coordinate descent methods and faster algorithms for solving linear systems"

Connected through hyperedge HE-2 (induced by source paper "algorithmic interpretations of fractal dimension"):
  with members:
    - "the limited blessing of low dimensionality when 1 1 d is the best possible exponent for d dimensional geometric problems"
    - "the traveling salesman problem low dimensionality implies a polynomial time approximation scheme"
    - "fast construction of nets in low dimensional metrics and their applications"

Connected through hyperedge HE-3 (induced by source paper "approximation algorithms for polynomial expansion and low density graphs"):
  with members:
    - "approximation algorithms for low density graphs"
    - "simple ptas s for families of graphs excluding a minor"
    - "net and prune a linear time algorithm for euclidean distance problems"
    - "qptas for geometric set cover problems via optimal separators"
    - "quasi polynomial time approximation scheme for sparse subsets of polygons"
    - "deciding first order properties of nowhere dense graphs"
    - "approximation schemes for maximum weight independent set of rectangles"
    - "approximation algorithms for maximum independent set of pseudo disks"

Connected through hyperedge HE-4 (induced by source paper "approximation algorithms for low density graphs"):
  with members:
    - "simple ptas s for families of graphs excluding a minor"
    - "net and prune a linear time algorithm for euclidean distance problems"
    - "qptas for geometric set cover problems via optimal separators"
    - "quasi polynomial time approximation scheme for sparse subsets of polygons"
    - "approximation schemes for maximum weight independent set of rectangles"
    - "approximation algorithms for maximum independent set of pseudo disks"
    - "being fat and friendly is not enough"
    - "improved approximation algorithms for geometric set cover"

Connected through hyperedge HE-5 (induced by source paper "separating a voronoi diagram"):
  with members:
    - "approximation algorithms for maximum independent set of pseudo disks"

Connected through hyperedge HE-6 (induced by source paper "quasi polynomial time approximation scheme for sparse subsets of polygons"):
  with members:
    - "qptas for geometric set cover problems via optimal separators"
    - "approximation schemes for maximum weight independent set of rectangles"
    - "approximation algorithms for maximum independent set of pseudo disks"
    - "geometric packing under non uniform constraints"
    - "being fat and friendly is not enough"

Connected through hyperedge HE-7 (induced by source paper "separating a voronoi diagram via local search"):
  with members:
    - "approximation algorithms for maximum independent set of pseudo disks"
    - "simpler analyses of local search algorithms for facility location"

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.CG(Computational Geometry)