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A universal continuum of weight
Authors:Alan Dow   Klaas Pieter Hart
Affiliation:Department of Mathematics and Statistics, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3 ; Faculty of Technical Mathematics and Informatics, TU Delft, Postbus 5031, 2600 GA Delft, The Netherlands
Abstract:

We prove that every continuum of weight $aleph_1$ is a continuous image of the Cech-Stone-remainder $R^*$ of the real line. It follows that under  $mathsf{CH}$ the remainder of the half line $[0,infty)$ is universal among the continua of weight  $mathfrak{c}$-- universal in the `mapping onto' sense.

We complement this result by showing that 1) under  $mathsf{MA}$ every continuum of weight less than  $mathfrak{c}$ is a continuous image of $R^*$, 2) in the Cohen model the long segment of length  $omega_2+1$ is not a continuous image of $R^*$, and 3)  $mathsf{PFA}$ implies that $I_u$ is not a continuous image of $R^*$, whenever $u$ is a $mathfrak{c}$-saturated ultrafilter.

We also show that a universal continuum can be gotten from a $mathfrak{c}$-saturated ultrafilter on $omega$, and that it is consistent that there is no universal continuum of weight  $mathfrak{c}$.

Keywords:Paroviv{c}enko's theorem   universal continuum   remainder of $[0  infty)$   $aleph_1$-saturated model   elementary equivalence   Continuum Hypothesis   Cohen reals   long segment   Martin's Axiom   Proper Forcing Axiom   saturated ultrafilter
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