Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dealing with the exponential wall in electronic structure calculations   An alternative to Density Functional Theory are wavefunction based electronic
structure calculations for solids. In order to perform them the Exponential
Wall (EW) problem has to be resolved. It is caused by an exponential increase
of the number of configurations with increasing electron number N. There are
different routes one may follow. One is to characterize a many-electron
wavefunction by a vector in Liouville space with a cumulant metric rather than
in Hilbert space. This removes the EW problem. Another is to model the solid by
an {\it impurity} or {\it fragment} embedded in a {\it bath} which is treated
at a much lower level than the former. This is the case in Density Matrix
Embedding Theory (DMET) or Density Embedding Theory (DET). The latter are
closely related to a Schmidt decomposition of a system and to the determination
of the associated entanglement. We show here the connection between the two
approaches. It turns out that the DMET (or DET) has an identical active space
as a previously used Local Ansatz, based on a projection and partitioning
approach. Yet, the EW problem is resolved differently in the two cases. By
studying a $H_{10}$ ring these differences are analyzed with the help of the
method of increments.

2
The categories of this paper are: math
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ