文摘
We consider the instationary Navier–Stokes equations in a smooth exterior domain \({\Omega \subseteq \mathbb{R}^3}\) with initial value u 0, external force f =?div? F and viscosity ν. It is an important question to characterize the class of initial values \({u_0\in L^2_{\sigma}(\Omega)}\) that allow a strong solution \({u \in L^s(0,T; L^q(\Omega))}\) in some interval \({[0,T[ \, , 0 where s, q with 3 q ?/em> and \({\frac{2}{s} + \frac{3}{q} =1}\) are so-called Serrin exponents. In Farwig and Komo (Analysis (Munich) 33:101-19, 2013) it is proved that \({\int_0^{\infty} \| e^{-\nu t A} u_0 \|_q^{s} \, {d}t is necessary and sufficient for the existence of a strong solution \({u \in L^s(0,T ; L^q(\Omega)) \, , 0 , if additionally 3 q ?8; here, A denotes the Stokes operator. In this paper, we will show that this result remains true if q >?8, and consequently, \({\int_0^{\infty} \| e^{-\nu t A} u_0 \|_q^{s} \, {d}t is the optimal initial value condition to obtain such a strong solution for all possible Serrin exponents s, q.