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: "frozen variables in random boolean constraint satisfaction problems"
  Abstract: We determine the exact freezing threshold, r^f, for a family of models of random boolean constraint satisfaction problems, including NAE-SAT and hypergraph 2-colouring, when the constraint size is sufficiently large. If the constraint-density of a random CSP, F, in our family is greater than r^f then for almost every solution of F, a linear number of variables are frozen, meaning that their colours cannot be changed by a sequence of alterations in which we change o(n) variables at a time, always switching to another solution. If the constraint-density is less than r^f, then almost every solution has o(n) frozen variables. #R##N#Freezing is a key part of the clustering phenomenon that is hypothesized by non-rigorous techniques from statistical physics. The understanding of clustering has led to the development of advanced heuristics such as Survey Propogation. It has been suggested that the freezing threshold is a precise algorithmic barrier: that for densities below r^f the random CSPs can be solved using very simple algorithms, while for densities above r^f one requires more sophisticated techniques in order to deal with frozen clusters.

Connected through hyperedge HE-1 (induced by source paper "planting colourings silently"):
  with members:
    - "the condensation phase transition in random graph coloring"
    - "chasing the k colorability threshold"
    - "reconstruction and clustering in random constraint satisfaction problems"

Connected through hyperedge HE-2 (induced by source paper "inside the clustering window for random linear equations"):
  with members:
    - "on independent sets in random graphs"
    - "the set of solutions of random xorsat formulae"
    - "chasing the k colorability threshold"
    - "catching the k naesat threshold"
    - "the solution space geometry of random linear equations"
    - "reconstruction and clustering in random constraint satisfaction problems"
    - "tight thresholds for cuckoo hashing via xorsat"
    - "survey propagation an algorithm for satisfiability"

Connected through hyperedge HE-3 (induced by source paper "inside the clustering threshold for random linear equations"):
  with members:
    - "on independent sets in random graphs"
    - "chasing the k colorability threshold"
    - "catching the k naesat threshold"
    - "reconstruction and clustering in random constraint satisfaction problems"
    - "tight thresholds for cuckoo hashing via xorsat"
    - "on the solution space geometry of random constraint satisfaction problems"
    - "a new look at survey propagation and its generalizations"

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)