Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Particle Number Conservation and Block Structures in Matrix Product
  States   The eigenvectors of the particle number operator in second quantization are
characterized by the block sparsity of their matrix product state
representations. This is shown to generalize to other classes of operators.
Imposing block sparsity yields a scheme for conserving the particle number that
is commonly used in applications in physics. Operations on such block
structures, their rank truncation, and implications for numerical algorithms
are discussed. Explicit and rank-reduced matrix product operator
representations of one- and two-particle operators are constructed that operate
only on the non-zero blocks of matrix product states.

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The categories of this paper are: q-bio
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
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The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: acc-phys
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
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The categories of this paper are: dg-ga