Can a Small Forcing Create Kurepa Trees

In the paper we probe the possibilities of creating a Kurepa tree in a generic extension of a model of CH plus no Kurepa trees by an ω1-preserving forcing notion of size at most ω1. In the first section we show that in the Lévy model obtained by collapsing all cardinals between ω1 and a strongly inaccessible cardinal by forcing with a countable support Lévy collapsing order many ω1preserving forcing notions of size at most ω1 including all ω-proper forcing notions and some proper but not ω-proper forcing notions of size at most ω1 do not create Kurepa trees. In the second section we construct a model of CH plus no Kurepa trees, in which there is an ω-distributive Aronszajn tree such that forcing with that Aronszajn tree does create a Kurepa tree in the generic extension. At the end of the paper we ask three questions.