We gratefully acknowledge financial support by CONCYTEC Peru within the program Programa nacional de innovación para la competitividad y productividad (PNICP, 361-PNICP-PIBA-2014) as well as travel support by the Heidelberg Graduate School of Mathematical and Computational Methods for the Sciences (HGS MathComp). The second author was supported by the DFG Research Scholarship FR3935/1-1.