Author/Authors :
Bonanzinga، نويسنده , , Maddalena and Cammaroto، نويسنده , , Filippo and Matveev، نويسنده , , Mikhail، نويسنده ,
Abstract :
All spaces are assumed to be Tychonoff. A space X is called projectively P (where P is a topological property) if every continuous second countable image of X is P . Characterizations of projectively Menger spaces X in terms of continuous mappings f : X → R ω , of Menger base property with respect to separable pseudometrics and a selection principle restricted to countable covers by cozero sets are given. If all finite powers of X are projectively Menger, then all countable subspaces of C p ( X ) have countable fan tightness. The class of projectively Menger spaces contains all Menger spaces as well as all σ-pseudocompact spaces, and all spaces of cardinality less than d . Projective versions of Hurewicz, Rothberger and other selection principles satisfy properties similar to the properties of projectively Menger spaces, as well as some specific properties. Thus, X is projectively Hurewicz iff C p ( X ) has the Monotonic Sequence Selection Property in the sense of Scheepers; βX is Rothberger iff X is pseudocompact and projectively Rothberger. Embeddability of the countable fan space V ω into C p ( X ) or C p ( X , 2 ) is characterized in terms of projective properties of X.
Keywords :
Projectively Hurewicz space , Pseudometric , The countable fan space , Functionally countable space , Tightness , Property C , Pseudocompact space , Fan tightness , Arhangelskiiיs ? i properties , Lindel?f space , C ? -embedded set , Fréchet space , AP-space , Projectively ( ? ) -space , Strong measure zero , C p ( X ) , Property (?) , cov ( M ) , ?-Cover , Property ( ? ) , P , Reznichenko property , Projectively countable space , ?-space , Haver property , Rothberger space , d , Weakly Fréchet space , Zero set , Strong fan tightness , QN-space , Projectively Rothberger space , Menger base property , ?-space , Projectively (?)-space , Scattered space , Monotonic sequence selection property , Hurewicz space , Cardinal numbers b , Weakly Fréchet in the strict sense space , Projectively Menger space , add ( M ) , ?-Cover , Cozero set , Sequential space , wQN-space , Menger space , Zero-dimensional space , Strictly Fréchet space , AP ? -space