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: "minimum cost homomorphisms to reflexive digraphs"
  Abstract: For digraphs $G$ and $H$, a homomorphism of $G$ to $H$ is a mapping $f:\ V(G)\dom V(H)$ such that $uv\in A(G)$ implies $f(u)f(v)\in A(H)$. If moreover each vertex $u \in V(G)$ is associated with costs $c_i(u), i \in V(H)$, then the cost of a homomorphism $f$ is $\sum_{u\in V(G)}c_{f(u)}(u)$. For each fixed digraph $H$, the {\em minimum cost homomorphism problem} for $H$, denoted MinHOM($H$), is the following problem. Given an input digraph $G$, together with costs $c_i(u)$, $u\in V(G)$, $i\in V(H)$, and an integer $k$, decide if $G$ admits a homomorphism to $H$ of cost not exceeding $k$. We focus on the minimum cost homomorphism problem for {\em reflexive} digraphs $H$ (every vertex of $H$ has a loop). It is known that the problem MinHOM($H$) is polynomial time solvable if the digraph $H$ has a {\em Min-Max ordering}, i.e., if its vertices can be linearly ordered by $<$ so that $i<j, s<r$ and $ir, js \in A(H)$ imply that $is \in A(H)$ and $jr \in A(H)$. We give a forbidden induced subgraph characterization of reflexive digraphs with a Min-Max ordering; our characterization implies a polynomial time test for the existence of a Min-Max ordering. Using this characterization, we show that for a reflexive digraph $H$ which does not admit a Min-Max ordering, the minimum cost homomorphism problem is NP-complete. Thus we obtain a full dichotomy classification of the complexity of minimum cost homomorphism problems for reflexive digraphs.

Connected through hyperedge HE-1 (induced by source paper "extensions of the minimum cost homomorphism problem"):
  with members:
    - "duality for min max orderings and dichotomy for min cost homomorphisms"
    - "minimum cost and list homomorphisms to semicomplete digraphs"

Connected through hyperedge HE-2 (induced by source paper "finding small separators in linear time via treewidth reduction"):
  with members:
    - "contracting graphs to paths and trees"
    - "obtaining a bipartite graph by contracting few edges"
    - "on multiway cut parameterized above lower bounds"
    - "multicut is fpt"
    - "fixed parameter tractability of multicut parameterized by the size of the cutset"
    - "treewidth reduction for constrained separation and bipartization problems"
    - "almost 2 sat is fixed parameter tractable"
    - "minimum cost homomorphisms to proper interval graphs and bigraphs"

Connected through hyperedge HE-3 (induced by source paper "duality for min max orderings and dichotomy for min cost homomorphisms"):
  with members:
    - "a maximal tractable class of soft constraints"
    - "minimum cost and list homomorphisms to semicomplete digraphs"

Connected through hyperedge HE-4 (induced by source paper "minimum cost homomorphisms to locally semicomplete and quasi transitive digraphs"):
  with members:
    - "a maximal tractable class of soft constraints"
    - "minimum cost and list homomorphisms to semicomplete digraphs"
    - "minimum cost homomorphisms to semicomplete multipartite digraphs"

Connected through hyperedge HE-5 (induced by source paper "minimum cost homomorphisms to semicomplete multipartite digraphs"):
  with members:
    - "a maximal tractable class of soft constraints"
    - "minimum cost and list homomorphisms to semicomplete digraphs"

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)