A cardinal inequality for topological spaces involving closed discrete sets
A cardinal inequality for topological spaces involving closed discrete sets
Let <italic>X</italic> be a <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper T 1"> <mml:semantics> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mi>T</mml:mi> <mml:mn>1</mml:mn> </mml:msub> </mml:mrow> <mml:annotation encoding="application/x-tex">{T_1}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> topological space. Let <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="a left-parenthesis upper X right-parenthesis equals sup left-brace alpha colon upper X"> <mml:semantics> <mml:mrow> <mml:mi>a</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>X</mml:mi> <mml:mo …