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Inspired by multiaccess in dense cellular systems, the paper first considers minimizing the determinant of the sum of a subset of n i.i.d. central Wishart matrices, for any given size. When n goes to infinity, the exact scaling for more general case, selecting a subset to minimize the product-determinant-sum of n i.i.d. central Wishart matrix vectors, is provided. Specifically, suppose each vector has K Wishart matrices of format GG with G of dimension N _r × N _t . Then for any subset of size n ^α , the K determinants, each being the sum over one of the vector elements, will have a product no less than exp{K N _r (1+ 1/K N _r N _t )(α - α*) log n}, for all a between α* := 1/(1 + K N _r N _t ) and 1. The paper then applies the results to study multiaccess with cross-cell collaborations in dense environment. When each cell allows multi-users to be on and decodes by treating signals from neighboring cells as noise, the maximum throughput is …