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<p>to <a href="page.php?w=topological_space">topological space</a>s. Different compactifications may exist for a given space, but arbitrary topological space admits <a href="page.php?w=Alexandroff_extension">Alexandroff extension</a>, also called the one-point <a href="page.php?w=compactification_%28mathematics%29">compactification</a> when the original space is not itself <a href="page.php?w=compact_space">compact</a>.  Projective line (over arbitrary field) is the Alexandroff extension of the corresponding field. Thus, the circle is the one-point</p><p>
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