On coverings of Banach spaces and their subsets by hyperplanes
On coverings of Banach spaces and their subsets by hyperplanes
Given a Banach space we consider the $\sigma$-ideal of all of its subsets which are covered by countably many hyperplanes and investigate its standard cardinal characteristics as the additivity, the covering number, the uniformity, the cofinality. We determine their values for separable Banach spaces, and approximate them for nonseparable Banach …