The main novelty of the problem under consideration resides in the non-trivial grouping of the densities: in particular, we assume that the interaction parameters formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0362546X15003685&_mathId=si7.gif&_user=111111111&_pii=S0362546X15003685&_rdoc=1&_issn=0362546X&md5=548fc00480025d3cc9ebeaf43d2c99f5" title="Click to view the MathML source">aij are only non-negative, and thus may vanish for specific couples formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0362546X15003685&_mathId=si8.gif&_user=111111111&_pii=S0362546X15003685&_rdoc=1&_issn=0362546X&md5=e283661e9e11d70906137e04af7a19f0" title="Click to view the MathML source">(i,j). As a main consequence, in the limit formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0362546X15003685&_mathId=si6.gif&_user=111111111&_pii=S0362546X15003685&_rdoc=1&_issn=0362546X&md5=2c4cf03e416a5913218477d60a4ae226" title="Click to view the MathML source">β→+∞, densities do not segregate pairwise in general, but are grouped in classes which, in turn, form a mutually disjoint partition. Moreover, with respect to the literature, we consider more general forcing terms, sign-changing solutions, and an arbitrary formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0362546X15003685&_mathId=si10.gif&_user=111111111&_pii=S0362546X15003685&_rdoc=1&_issn=0362546X&md5=514214ef983644b9c47f461e84b68800" title="Click to view the MathML source">p>0. In addition, we present a regularity theory of the emerging free-boundary, defined by the interface among different segregated groups.
These equations are very common in the study of Bose–Einstein condensates and are of key importance for the analysis of optimal partition problems related to high order eigenvalues.