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ORDER-THEORETIC INVARIANTS IN SET-THEORETIC TOPOLOGY

ORDER-THEORETIC INVARIANTS IN SET-THEORETIC TOPOLOGY

ORDER-THEORETIC INVARIANTS IN SET-THEORETIC TOPOLOGY

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ordered lexicographically, has π-weight ω and weight c, and is known to be compact and<br />

homogeneous. By Proposition 3.2.22, it has Noetherian type c + .<br />

Theorem 3.2.24. Suppose X is a Suslin line. Then πNt(X) ≥ ω1.<br />

Proof. Let A be a π-base of X consisting only of open intervals. By Lemma 3.2.20,<br />

it suffices to show that A is not ω op -like. Construct a sequence 〈Bn〉n

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