Blocking sets in projective spaces

In this paper we collect results on the possible sizes of k-blocking sets. Sinceprevious surveys focused mainly on blocking sets in the plane, we concentrate ourattention on blocking sets in higher dimensions. Lower bounds on the size of thesmallest non-trivial k-blocking set are surveyed in detail. The linearity conjecture andknown results supporting the conjecture (e.g. proofs in particular cases) are collected.The known constructions are also presented. In case of planar minimal blocking setswe only discuss the constructions briefly. In case of higher dimensions the situation isnot satisfactory, there are more open questions than known constructions. Keywords: (Semi-)ovoid; Blocking set; Minihyper; Redei type