Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Method For Making 2-Electron Response Reduced Density Matrices
  Approximately N-representable   In methods like geminal-based approaches or coupled cluster that are solved
using the projected Schr\"odinger equation, direct computation of the
2-electron reduced density matrix (2-RDM) is impractical and one falls back to
a 2-RDM based on response theory. However, the 2-RDMs from response theory are
not $N$-representable. That is, the response 2-RDM does not correspond to an
actual physical $N$-electron wave function. We present a new algorithm for
making these non-$N$-representable 2-RDMs approximately $N$-representable, i.e.
it has the right symmetry and normalization and it fulfills the $P$-, $Q$- and
$G$-conditions. Next to an algorithm which can be applied to any 2-RDM, we have
also developed a 2-RDM optimization procedure specifically for seniority-zero
2-RDMs. We aim to find the 2-RDM with the right properties that is the closest
(in the sense of the Frobenius norm) to the non-N-representable 2-RDM by
minimizing the square norm of the difference between the initial 2-RDM and the
targeted 2-RDM under the constraint that the trace is normalized and the 2-RDM,
$Q$- and $G$-matrices are positive semidefinite, i.e. their eigenvalues are
non-negative. Our method is suitable for fixing non-N-respresentable 2-RDMs
which are close to being N-representable. Through the N-representability
optimization algorithm we add a small correction to the initial 2-RDM such that
it fulfills the most important N-representability conditions.

28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph