Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pair extended coupled cluster doubles   The accurate and efficient description of strongly correlated systems remains
an important challenge for computational methods. Doubly occupied configuration
interaction (DOCI), in which all electrons are paired and no correlations which
break these pairs are permitted, can in many cases provide an accurate account
of strong correlations, albeit at combinatorial computational cost. Recently,
there has been significant interest in a method we refer to as pair coupled
cluster doubles (pCCD), a variant of coupled cluster doubles in which the
electrons are paired. This is simply because pCCD provides energies nearly
identical to those of DOCI, but at mean-field computational cost (disregarding
the cost of the two-electron integral transformation). Here, we introduce the
more complete pair extended coupled cluster doubles (pECCD) approach which,
like pCCD, has mean-field cost and reproduces DOCI energetically. We show that
unlike pCCD, pECCD also reproduces the DOCI wave function with high accuracy.
Moreoever, pECCD yields sensible albeit inexact results even for attractive
interactions where pCCD breaks down.

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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
10
The categories of this paper are: q-bio