ORDER-THEORETIC INVARIANTS IN SET-THEORETIC TOPOLOGY

More documents

Recommendations

Info

Proof. Let A be a base of X of size at most w(X). Let B be a π-base of X of size at most π(X). For each 〈U, V 〉 ∈ B 2 satisfying U ⊆ V , choose a closed Gδ-set Φ(U, V ) such that U ⊆ Φ(U, V ) ⊆ V . Then ran Φ, ordered by ⊆, is σ-centered because d(X) = ω. Since |A| < p, there is a filter G of ran Φ such that for all disjoint U, V ∈ A some K ∈ G satisfies U ∩ K = ∅ or V ∩ K = ∅. Hence, there exists a unique p ∈ G. Hence, p has pseudocharacter, and therefore character, at most |G|, which is at most π(X). Theorem 3.2.15. If X is a homogeneous compactum and ω = d(X) ≤ w(X) < p, then χNt(X) = ω. Proof. By Lemma 3.2.14, χ(X) ≤ π(X) = πχ(X)d(X) = πχ(X). Hence, by Theo- rem 3.2.13, χNt(X) = ω. Recall the most basic definitions and notation for amalgams. Definition 3.2.16. Suppose X is a T0 space, S is a subbase of X such that ∅ ∈ S , and 〈YS〉S∈S is a sequence of nonempty spaces. The amalgam Y of 〈YS : S ∈ S 〉 is defined by setting Y = p∈X such that, for each S ∈ S and open U ⊆ YS, the set π −1 S 55 p∈S∈S YS and declaring Y to have the weakest topology U is open in Y where π−1U = {p ∈ Y : S ∈ dom p and p(S) ∈ U}. Define π : Y → X by {π(p)} = dom p for all p ∈ Y . It is easily verified that π is continuous. Theorem 3.2.17. Suppose X, S , 〈YS〉S∈S , and Y are as in Definition 3.2.16. Then we have the following relations for all p ∈ Y . Nt(Y ) ≤ Nt(X) sup Nt(YS) S∈S πNt(Y ) ≤ πNt(X) sup πNt(YS) S∈S χNt(p, Y ) ≤ χNt(π(p), X) sup S∈dom p χNt(p(S), YS) S
Proof. We will only prove the first relation; the proofs of the others are almost identical. Set κ = Nt(X) sup S∈S Nt(YS). Let A be a κ op -like base of X. For each S ∈ S , let BS be a κ op -like base of YS. Set C = π −1 U ∩ S∈dom τ π −1 S τ(S) : τ ∈ F∈[S ]
Page 1 and 2:
ORDER-THEORETIC INVARIANTS IN SET-T
Page 3 and 4:
compactum without reducing its cell
Page 5 and 6:
Contents Abstract i Acknowledgement
Page 7 and 8:
Bibliography 160 vi
Page 9 and 10:
of certain products of homogeneous
Page 11 and 12: An ordinal α is regular if α = cf
Page 13 and 14: • regular if for all closed C ⊆
Page 15 and 16: • locally κ-compact if for every
Page 17 and 18: The category of boolean algebras is
Page 19 and 20: B is a base of X if and only if, fo
Page 21 and 22: A regular cardinal κ is a caliber
Page 23 and 24: the supremum of the local Noetheria
Page 25 and 26: • An subset S of M n is definable
Page 27 and 28: 1.7 Forcing Definition 1.7.1. The C
Page 29 and 30: • M[G] |= ϕ(σ (0) G , . . . ,
Page 31 and 32: • a reduction of a map g : Q →
Page 33 and 34: Definition 1.7.16. The product P ×
Page 35 and 36: If S is a stationary subset of a re
Page 37 and 38: Chapter 2 Amalgams 2.1 Introduction
Page 39 and 40: properties to this particular conne
Page 41 and 42: Theorem 2.2.2. The classes listed b
Page 43 and 44: Theorem 2.2.3. Suppose X and YS are
Page 45 and 46: Definition 2.2.7. Suppose W is a su
Page 47 and 48: y Theorem 2.3.1, ˜ Y is path-conne
Page 49 and 50: compactum with cellularity c. Moreo
Page 51 and 52: y(Si) for all i < m. Let W be an op
Page 53 and 54: Chapter 3 Noetherian types of homog
Page 55 and 56: Finally, in Section 3.5, we prove s
Page 57 and 58: Given Theorem 3.2.2, justifying Obs
Page 59 and 60: and V ∈ Bm and U V . Then m = n
Page 61: Definition 3.2.12. Given a space X,
Page 65 and 66: Proof. Let A be a neighborhood base
Page 67 and 68: We may assume there exists an n <
Page 69 and 70: intervals i∈I (ai, bi) such that
Page 71 and 72: p ≥ q iff, for all σ ∈ ζ and
Page 73 and 74: V ∈ V. By Theorem 3.3.2, Q is alm
Page 75 and 76: Proposition 3.3.11. Suppose a point
Page 77 and 78: than κ. Then a κ-approximation se
Page 79 and 80: κ. Let Υ(δγ) = 〈β0, . . . ,
Page 81 and 82: subset of Gα. For all I ⊆ P(2 κ
Page 83 and 84: such that V 1 ⊆ W . Therefore, h
Page 85 and 86: we have A, N , Mα ∈ Mα+1 ≺ H
Page 87 and 88: We prove this claim by induction. F
Page 89 and 90: Proof. Let 〈Xi〉i∈I be a seque
Page 91 and 92: Set A = Aκ∪Aλ∪Ap. Let us show
Page 93 and 94: exists τ ∈ [Aα]
Page 95 and 96: Theorem 3.4.3. If κ ≥ ω and B h
Page 97 and 98: The following theorem is implicit i
Page 99 and 100: W ⊆ f −1 {0}. By (3) for stage
Page 101 and 102: 3.5 More on local Noetherian type I
Page 103 and 104: has an open neighborhood Wx that is
Page 105 and 106: for all σ ∈ [U]
Page 107 and 108: Lemma 3.5.14. Suppose X is a space,
Page 109 and 110: πNt(X) ≥ ω1? Question 3.6.3. Su
Page 111 and 112: Theorem 4.1.3. If X is a homogeneou
Page 113 and 114:
ase of X? Is there such a metric sp
Page 115 and 116:
Set Uα = i
Page 117 and 118:
Corollary 4.2.15. Let X be a compac
Page 119 and 120:
Corollary 4.2.19 (GCH). There do no
Page 121 and 122:
finite cover of X and pairwise ⊆-
Page 123 and 124:
w = min([p1, max X] \ U). Then w
Page 125 and 126:
points p of Y , there exists α <
Page 127 and 128:
x ∈ [ω] ω splits every y ∈ A.
Page 129 and 130:
Lemma 5.2.6. Let X be a compact spa
Page 131 and 132:
κ ss2 ≤ κ. Every nontrivial fin
Page 133 and 134:
Proof. Let P be the κ-long finite
Page 135 and 136:
Remark 5.4.2. If P is a finite supp
Page 137 and 138:
Let J be the P-name {〈ˇα, pα
Page 139 and 140:
are no such α and β, then let Qσ
Page 141 and 142:
For each α < λ, let xα be the Co
Page 143 and 144:
Proof. See Exercise A12 on page 289
Page 145 and 146:
Let Fλα+β to be a Pλα+β-name
Page 147 and 148:
Proof. Fix p ∈ ω ∗ . By a resu
Page 149 and 150:
χ(〈p〉i
Page 151 and 152:
Then χ(p, X) < w(X) or Nt(X) > µ.
Page 153 and 154:
Question 5.7.10. Is cf c < χNt(ω
Page 155 and 156:
• P ≤T P × Q. • P ≤T R ≥
Page 157 and 158:
changed. Moreover, since ω × ω1
Page 159 and 160:
Theorem 6.3.7. Assume ♦(E c ω) a
Page 161 and 162:
assumption that c = κ + for some c
Page 163 and 164:
show that, for a fixed regular unco
Page 165 and 166:
and i ∈ dom Γ such that for all
Page 167 and 168:
Bibliography [1] O. T. Alas, M. G.
Page 169 and 170:
[20] R. Engelking, General Topology
Page 171 and 172:
[39] K. Kunen, Weak P-points in N
Page 173 and 174:
[60] B. É. ˇ Sapirovskiĭ, Cardin
show all

ORDER-THEORETIC INVARIANTS IN SET-THEORETIC TOPOLOGY

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?