共 4 条
YT MORE ON CARDINALITY BOUNDS INVOLVING THE WEAK LINDELOF DEGREE
被引:6
|作者:
Bella, A.
[1
]
Carlson, N.
[2
]
Gotchev, I.
[3
]
机构:
[1] Univ Catania, Dept Math, Viale A Doria 6, I-95125 Catania, Italy
[2] Calif Lutheran Univ, Dept Math, 60 W Olsen Rd,MC 3750, Thousand Oaks, CA 91360 USA
[3] Cent Connecticut State Univ, Dept Math Sci, 1615 Stanley St, New Britain, CT 06050 USA
关键词:
Cardinal function;
weak Lindelof degree;
(discrete) cellularity;
discrete countable chain condition (DCCC);
star-DCCC space;
(strong) G(delta)-diagonal of rank n;
extremally disconnected;
locally compact;
SPACES;
RANK;
SUBMETRIZABILITY;
EXTENT;
D O I:
10.2989/16073606.2022.2040634
中图分类号:
O1 [数学];
学科分类号:
0701 ;
070101 ;
摘要:
We give several new bounds for the cardinality of a Hausdorff topological space X involving the weak Lindelof degree omega L(X). In particular, we show that if X is extremally disconnected, then |X| <= 2(omega L(X)pi chi(X)psi(X)), and if X is additionally power homogeneous, then vertical bar X vertical bar <= 2(omega L(X)pi chi(X)). We also prove that if X is a star-DCCC space with a G(delta) -diagonal of rank 3, then vertical bar X vertical bar <= 2(aleph 0) ; and if X is any normal star-DCCC space with a G(delta) -diagonal of rank 2, then vertical bar X vertical bar <= 2(aleph 0). Several improvements of results in [10] are also given. We show that if X is locally compact, then vertical bar X vertical bar <= omega L(X)(psi(X)) and that vertical bar X vertical bar <= omega L(X)(t(X)) if X is additionally power homogeneous. We also prove that vertical bar X vertical bar <= 2(psi c) ((X)t(X) omega L(X)) for any space with a pi-base whose elements have compact closures and that the stronger inequality vertical bar X vertical bar <=omega L(X)(psi c) ((X)t(X)) is true when X is locally H-closed or locally Lindelof.
引用
收藏
页码:745 / 760
页数:16
相关论文