Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Assessing the Orbital-Optimized Unitary Ansatz for Density Cumulant
  Theory   The previously proposed ansatz for density cumulant theory that combines
orbital-optimization and a parameterization of the 2-electron reduced density
matrix cumulant in terms of unitary coupled cluster amplitudes (OUDCT) is
carefully examined. Formally, we elucidate the relationship between OUDCT and
orbital-optimized unitary coupled cluster theory and show the existence of
near-zero denominators in the stationarity conditions for both the exact and
some approximate OUDCT methods. We implement methods of the OUDCT ansatz
restricted to double excitations for numerical study, up to the fifth
commutator in the Baker-Campbell-Hausdorff expansion. We find that methods
derived from the ansatz beyond the previously known ODC-12 method tend to be
less accurate for equilibrium properties and less reliable when attempting to
describe $H2$ dissociation. New developments are needed to formulate more
accurate DCT variants.

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The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: cond-mat
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: eess
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The categories of this paper are: nucl-th