Let Ω⊂RN be an open set. In this work we consider solutions of the following gradient elliptic system −div(A(x)∇ui,β)=fi(x,ui,β)+a(x)β|ui,β|γ−1ui,β∑j=1j≠il|uj,β|γ+1,for i=1,…,l. We work in the competitive case, namely β<0. Under suitable assumptions on A, a, fi and on the exponent γ, we prove that uniform L∞–bounds on families of positive solutions {uβ}β<0={(u1,β,…,ul,β)}β<0 imply uniform Lipschitz bounds (which are optimal).One of the main points in the proof are suitable generalizations of Almgren’s and Alt–Caffarelli–Friedman’s monotonicity formulas for solutions of such systems. Our work generalizes previous results, where the case A(x)=Id (i.e. the operator is the Laplacian) was treated.
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