The code solves JIMWLK evolution equation using Langevin step method
Originally written by Björn Schenke, some modifications by Heikki Mäntysaari heikki.mantysaari@jyu.fi
The code can be built using cmake (needs GSL, FFTW and Boost libraries)
mkdir build
cd build
cmake ..
make
The binary file is generated in build/bin/jimwlk
The code reads one command line parameter which is the file name where all parameters are set.
Template file is provided, see file input
. The parameters in the input file are expained in detail in the
source file src/Parameters.h
The initial condition can either be generated at the beginning (initMethod 1-3
),
or one can read in a set of Wilson lines generated using the IPGlasma code (https://github.com/schenke/ipglasma)
(10
: txt format, 11
: binary format). The filename for the initial Wilson lines
is the input_wline parameter. The evolved Wilson lines are saved in
evolved_wilson_lines directory
, and the filename contains the number
of evolution steps s (filename format is inputfile_steps_s
).
At fixed coupling, steps
is related to the Bjorken x via
steps = alphas * log(x0/x)/ (pi*pi*ds),
where the timestep ds
is defined in input file and x0
can be taken to be 0.01 or so.
With running coupling,
steps=log(x0/x)/(pi*pi*ds)
In the input file, if simpleLangevin
is set to 1
, the JIMWLK is solved using the method from
arXiv:1212.4825 which does not require adjoint Wilson lines -> faster, and needs less memory
At running coupling, the parameter m
that suppresses long distance Coulomb tails is
given in GeV in the input file, see arXiv:1407.8458 for details.