Albiac Alesanco, Fernando JoséAnsorena, José L.Wojtaszczyk, Przemyslaw2021-09-062021-10-0820211139-113810.1007/s13163-020-00374-8https://academica-e.unavarra.es/handle/2454/40417We show how to construct non-locally convex quasi-Banach spaces X whose dual separates the points of a dense subspace of X but does not separate the points of X. Our examples connect with a question raised by Pietsch (Rev Mat Complut 22(1):209-226, 2009) and shed light into the unexplored class of quasi-Banach spaces with nontrivial dual which do not have sufficiently many functionals to separate the points of the space.13 p.application/pdfeng© Universidad Complutense de Madrid 2020Quasi-Banach spaceBanach envelopeExtension of operatorsPoint separation propertyinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccessAcceso abierto / Sarbide irekia