Funding for this research was provided by:
Directorate for Mathematical and Physical Sciences (1608223, 1105050, 1107263, 1107367)
Division of Mathematical Sciences (1107452)
Deutsche Forschungsgemeinschaft (SPP 2026)
Article History
Received: 22 February 2018
Accepted: 31 October 2018
First Online: 23 February 2019