On uniformly minimal and 'uniformly complete' exponential systems

A.Olevskii and A.Ulanovskii obtained a scale of density results, which correspond to how well an exponential system approximates a uniformly minimal system over a compact set. We extend their result in several directions. First, we show that it holds for any set of positive finite measure. Next, we consider a relaxed version of frames, which we term ‘uniformly complete systems’, and obtain an analogues scale of density results for such systems.