ON THE CARDINALITY OF URYSOHN SPACES AND WEAKLY H-CLOSED SPACES

被引：1
|
作者：
Basile, Fortunata Aurora [1 ]
Carlson, Nathan [2 ]
机构：
[1] Univ Messina, Piazza Pugliatti 1, I-98122 Messina, Italy
[2] Calif Lutheran Univ, Dept Math, 60 W Olsen Rd, Thousand Oaks, CA 91360 USA
来源：
MATHEMATICA BOHEMICA | 2019年 / 144卷 / 03期
关键词：
Urysohn space; theta-closure; pseudocharacter; almost Lindelof degree; cardinality; cardinal invariant;
D O I：
10.21136/MB.2018.0037-18
中图分类号：
O1 [数学];
学科分类号：
0701 ; 070101 ;
摘要：
We introduce the cardinal invariant theta-aL'(X), related to theta-aL(X), and show that if X is Urysohn, then vertical bar X vertical bar <= 2(theta-aL'(x))(chi(X)). As theta-aL'(X) <= aL(X), this represents an improvement of the Bella-Cammaroto inequality. We also introduce the classes of firmly Urysohn spaces, related to Urysohn spaces, strongly semiregular spaces, related to semiregular spaces, and weakly H-closed spaces, related to H-closed spaces.
引用
收藏
页码：325 / 336
页数：12
相关论文
共 50 条
  • [1] On the cardinality of Hausdorff spaces and H-closed spaces
    Carlson, N. A.
    Porter, J. R.
    TOPOLOGY AND ITS APPLICATIONS, 2018, 241 : 377 - 395
  • [2] H-CLOSED SPACES
    JOSEPH, JE
    PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY, 1976, 55 (01) : 223 - 226
  • [3] On the cardinality of Urysohn spaces
    Cammaroto, Filippo
    Catalioto, Andrei
    Porter, Jack
    TOPOLOGY AND ITS APPLICATIONS, 2013, 160 (14) : 1862 - 1869
  • [4] ON THE CARDINALITY OF URYSOHN SPACES
    BELLA, A
    CAMMAROTO, F
    CANADIAN MATHEMATICAL BULLETIN-BULLETIN CANADIEN DE MATHEMATIQUES, 1988, 31 (02): : 153 - 158
  • [5] PROJECTIVENESS IN H-CLOSED SPACES
    BLASZCZYK, A
    COLLOQUIUM MATHEMATICUM, 1975, 32 (02) : 185 - 192
  • [6] HYPERSPACES OF H-CLOSED SPACES
    FRIEDLER, LM
    DICKMAN, RF
    KRYSTOCK, RL
    CANADIAN JOURNAL OF MATHEMATICS-JOURNAL CANADIEN DE MATHEMATIQUES, 1980, 32 (05): : 1072 - 1079
  • [7] CLOSED SUBSPACES OF H-CLOSED SPACES
    VERMEER, J
    PACIFIC JOURNAL OF MATHEMATICS, 1985, 118 (01) : 229 - 247
  • [8] On linearly H-closed spaces
    Alas, Ofelia T.
    Junqueira, Lucia R.
    Wilson, Richard G.
    TOPOLOGY AND ITS APPLICATIONS, 2019, 258 : 161 - 171
  • [9] SEQUENTIALLY H-CLOSED SPACES
    OVSEPIAN, SG
    DOKLADY AKADEMII NAUK SSSR, 1978, 238 (05): : 1055 - 1058
  • [10] Nearly H-closed spaces
    Osipov A.V.
    Journal of Mathematical Sciences, 2008, 155 (4) : 624 - 631
12345