Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Feynman's solution of the quintessential problem in solid state physics   Two of the most influential ideas developed by Richard Feynman are the
Feynman diagram technique and his variational approach. The former provides a
powerful tool to construct a systematic expansion for a generic interacting
system, while the latter allows optimization of a perturbation theory using a
variational principle. Here we show that combining a variational approach with
a new diagrammatic quantum Monte Carlo method, both based on the Feynman's
original ideas, results in a powerful and accurate solver to the generic solid
state problem, in which a macroscopic number of electrons interact by the long
range Coulomb repulsion. We apply the solver to the quintessential problem of
solid state, the uniform electron gas (UEG), which is at the heart of the
density functional theory (DFT) success in describing real materials, yet it
has not been adequately solved for over 90 years. While some wave-function
properties, like the ground state energy, have been very accurately calculated
by the diffusion Monte Carlo method (DMC), the static and dynamic response
functions, which are directly accessed by the experiment, and are crucial for
development of non-local and non-adiabatic density functionals, remain poorly
understood. Our method allows us to calculate the momentum-frequency resolved
spin response functions for the first time, and to improve on the precision of
the charge response function. The accuracy of both response functions is
sufficiently high, so as to uncover previously missed fine structure in these
responses. This method can be straightforwardly applied to a large number of
moderately interacting electron systems in the thermodynamic limit, including
realistic models of metallic and semiconducting solids.

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The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an