Funding for this research was provided by:
National Science Foundation (DMS-1306777, DMS-1407574)
Simons Foundation (306576, 338287)
Wisconsin Alumni Research Foundation
Strategic development fund at the University of Sussex
National Science Foundation (DMS-0747758)
Article History
Received: 13 October 2015
Revised: 18 June 2016
First Online: 2 August 2016