NSPT
Numerical stochastic perturbation theory
In numerical stochastic perturbation theory, the perturbation expansions
of the quantities of interest are obtained through a stochastic process.
Traditionally, the method is based on the Langevin equation, but other
stochastic processes can be used and may offer some technical advantages.
The method was introduced in
F. Di Renzo, G. Marchesini, P. Marenzoni, E. Onofri,
Lattice perturbation theory on the computer,
Nucl. Phys. Proc. Suppl. 34, 795 (1994)
(
Science Direct).
F. Di Renzo, E. Onofri, G. Marchesini, P. Marenzoni,
Four loop result in SU(3) lattice gauge theory ...,
Nucl. Phys. B426, 675 (1994)
(
Science Direct,
arXiv.org).
and was reviewed in
F. Di Renzo, L. Scorzato,
Numerical stochastic perturbation theory for full QCD,
JHEP 0410 (2004) 073
(
Science Direct,
arXiv.org).
The program package that can be downloaded from this page implements
the stochastic molecular dynamics (SMD) algorithm along the lines of
M. Dalla Brida, M. Lüscher,
SMD-based numerical stochastic perturbation,
CERN-TH-2017-057 (March 2017),
arXiv.org
A version of standard NSPT based on the Langevin equation is included as
well.
Program scope and features
Currently the only supported theory is the SU(3) gauge theory with Wilson
plaquette action on 4-dimensional N0 x N1 x
N2 x N3 lattices. Periodic boundary conditions are
assumed in the space directions and either Schrödinger functional (SF) or
open-SF boundary conditions in the time direction.
The Yang-Mills gradient flow is implemented as well and may optionally be
used for online measurements of the Yang-Mills action density at positive
flow time.
For the numerical integration of the stochastic equation, various
integration schemes are offered and can be chosen at run time. Among them
are up to 6th order OMF (Omelyan-Mryglod-Folk) integrators for the
molecular-dynamics equations and an efficient second order scheme for
the Langevin equation.
All programs parallelize in 0,1,2,3 or 4 dimensions, depending on what is
specified at compilation time. They are highly optimized for machines with
current Intel or AMD processors, but will run correctly on any system that
complies with the ISO C89 (formerly ANSI C) and the MPI 1.2 standards.
Documentation
The programs have a modular form, with strict prototyping and a minimal
use of external variables. Each program file contains a small number of
externally accessible functions whose functionality is described at the
top of the file.
The data layout is explained in various README files and detailed
instructions are given on how to run the main programs. A set of further
documentation files are included in the doc directory, where the
normalization conventions, the chosen algorithms and other important
program elements are described.
Authors
The current release of the NSPT package was written by Mattia Dalla Brida
and Martin Lüscher. Several modules were taken over from the
openQCD package.
Download
The publicly available NSPT release is
NSPT-1.4.tar.gz
The package contains the source code, usage instructions and other
documentation files. After unpacking, first read the README file in
the top directory.
License
The software may be used under the terms of the
GNU General Public Licence (GPL)
.
Last updated 14 March 2017