Olga Ladyzhenskaya

Olga Alexandrovna Ladyzhenskaya was a Soviet mathematician who made fundamental contributions to the theory of the Navier–Stokes equations. In the two-dimensional case, she proved the existence and uniqueness of smooth solutions for all times, which completely resolves the regularity problem in dimension 2. In the three-dimensional case, she proved the existence of weak solutions and obtained important results on local regularity: if a solution loses smoothness, this can happen only on a set of small measure. Her work on boundary value problems for hydrodynamic equations, including non-stationary problems, became classical and is widely used in modern research. She also developed methods of a priori estimates and functional analysis, which are applied in the study of the possibility of blow-up in finite time. Ladyzhenskaya is also known for her work on equations of mathematical physics, variational inequalities, and the theory of attractors. Her contribution to the Navier–Stokes problem is recognized worldwide: she was one of the first to systematically investigate the smoothness and uniqueness of solutions, and her results underlie many modern approaches to the millennium problem.