Python codes

Python codes for the bonus 2-hour lecture on the Non-Perturbative Renormalization Group, given at the ENS de Lyon for Master 2 students. The details of the method, as well as the derivation of the main equations are given for example in this helpful introduction arXiv:0712.203.

The first code solves the NPRG flow at the Local Potential Approximation for the Ising model in 2D, in the ordered phase. It generates an animation showing the flow of the effective potential (and its derivatives), and in particular the approach to convexity.

The second code solves the NPRG flow equation at the LPA for dimensionless variables, in order to find the Wilson-Fisher fixed point potential. The initial conditions of the flow are fine-tuned such that the flow goes to the fixed point of the 3D Ising model. An animation of the flow toward the fixed point potential is generated.

These codes work in python3 and use standard library such as scipy, numpy and matplotlib.

NB : python is generally not the fastest language to solve these kinds of problems, C or Fortran might be favored for a practical implementation.