TY - JOUR
T1 - C⁎-embedding and P-embedding in subspaces of products of ordinals
AU - Kemoto, Nobuyuki
AU - Usuba, Toshimichi
N1 - Funding Information:
This research was supported by Grant-in-Aid for Scientific Research (C) 21K03339.
Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2022/8/15
Y1 - 2022/8/15
N2 - It is known that in X=A×B, where A and B are subspaces of ordinals, all closed C⁎-embedded subspaces of X are P-embedded. Also it is asked whether all closed C⁎-embedded subspaces of X are P-embedded whenever X is a subspace of products of two ordinals. In this paper, we prove that both of the following are consistent with ZFC: • there is a subspace X of (ω+1)×ω1 such that the closed subspace X∩({ω}×ω1) is C⁎-embedded in X but not P-embedded in X, • for every subspace X of (ω+1)×ω1, if the closed subspace X∩({ω}×ω1) is C⁎-embedded in X, then it is P-embedded in X.
AB - It is known that in X=A×B, where A and B are subspaces of ordinals, all closed C⁎-embedded subspaces of X are P-embedded. Also it is asked whether all closed C⁎-embedded subspaces of X are P-embedded whenever X is a subspace of products of two ordinals. In this paper, we prove that both of the following are consistent with ZFC: • there is a subspace X of (ω+1)×ω1 such that the closed subspace X∩({ω}×ω1) is C⁎-embedded in X but not P-embedded in X, • for every subspace X of (ω+1)×ω1, if the closed subspace X∩({ω}×ω1) is C⁎-embedded in X, then it is P-embedded in X.
KW - 2<2
KW - Almost disjoint family
KW - C-embedding
KW - Consistent
KW - Independent family
KW - P-embedding
KW - Subspaces of products of ordinals
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U2 - 10.1016/j.topol.2022.108194
DO - 10.1016/j.topol.2022.108194
M3 - Article
AN - SCOPUS:85134487905
SN - 0166-8641
VL - 318
JO - Topology and its Applications
JF - Topology and its Applications
M1 - 108194
ER -