Fix Musker's law

Due to inconsistencies between the original paper by Musker and Malaspina's formulation, we used the wrong logarithm in the implementation of Musker's law (decimal instead of natural logarithm). This MR introduces the natural logarithm to fit Malaspina's formulation.

.gitlab-ci.yml

@@ -29,7 +29,7 @@ stages:
 tests-and-coverage:
   stage: pretest
   extends: .every-commit
-  image: i10git.cs.fau.de:5005/pycodegen/pycodegen/full
+  image: i10git.cs.fau.de:5005/pycodegen/pycodegen/full:cupy12.3
   script:
     # - pip install sympy --upgrade
     - export NUM_CORES=$(nproc --all)