Fourth-Order Operators with Unbounded Coefficients in \(L^1\) Spaces
摘要
We prove that operators of the form \(A=-a(x)^2\varDelta ^{2}\) , with suitable growth conditions on the coefficient a(x), generate analytic semigroups in \(L^1(\mathbb {R}^N)\) . In particular, we deduce generation results for the operator \(A :=- (1+|x|^2)^{\alpha } \varDelta ^{2}\) , \(0\le \alpha \le 2\) . Moreover, we characterize the maximal domain of A in \(L^1(\mathbb {R}^N)\) .