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Reflecting topological properties in closed separable subspaces

  • Alan Dow,
  • Vladimir V. Tkachuk

摘要

We establish that, for any metrizable space X, if every closed separable subspace of X has the Baire property, then the space X has the Baire property. The same reflection result holds for spaces \(C_p(X)\) C p ( X ) . It is also shown that all closed separable subspaces of \(C_p(X)\) C p ( X ) are Čech-complete if and only if X is a functionally countable P-space. If \(\overline{A}\) A ¯ is pseudocomplete for every countable set \(A\subset C_p(X)\) A C p ( X ) , then \(C_p(X)\) C p ( X ) is pseudocomplete. To show that zero-dimensionality does not reflect in closed separable subspaces of metrizable spaces, under Jensen’s Axiom \(\diamondsuit \) , we give an example of a connected metrizable space M such that \(\overline{A}\) A ¯ is countable and hence zero-dimensional for every countable set \(A\subset M\) A M .