Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90028-4
James R. Boone
A new property of pseudo-open functions is presented in this paper. Pseudo-open functions are monotonic decreasing with respect to ordinal and cardinal invariants defined by compact and sequential closures. A weak form of continuity, called k-continuous, is defined, characterized and used in the proof of the monotonicity properties of pseudo-open mappings. The relationships between the classes of k-continuous and sequentially continuous mappings in the category of all topological spaces and the continuous mappings in the subcategories of k-spaces and sequential spaces are presented.
{"title":"Pseudo-open functions are monotonic decreasing for ordinal and cardinal invariants","authors":"James R. Boone","doi":"10.1016/0016-660X(78)90028-4","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90028-4","url":null,"abstract":"<div><p>A new property of pseudo-open functions is presented in this paper. Pseudo-open functions are monotonic decreasing with respect to ordinal and cardinal invariants defined by compact and sequential closures. A weak form of continuity, called <em>k</em>-continuous, is defined, characterized and used in the proof of the monotonicity properties of pseudo-open mappings. The relationships between the classes of <em>k</em>-continuous and sequentially continuous mappings in the category of all topological spaces and the continuous mappings in the subcategories of <em>k</em>-spaces and sequential spaces are presented.</p></div>","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"9 3","pages":"Pages 243-251"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-660X(78)90028-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91638695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90029-6
S.W. Davis, G. Gruenhage, P.J. Nyikos
In this paper we answer questions of Arhangel'skii and Michael by providing an example of a regular symmetrizable space which is not subparacompact and has a closed subset which is not a Gσ-set. We also use the idea of sequential order to obtain some positive results, and several examples are provided which show that these results are in some sense the best possible.
{"title":"Gσ-sets in symmetrizable and related spaces","authors":"S.W. Davis, G. Gruenhage, P.J. Nyikos","doi":"10.1016/0016-660X(78)90029-6","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90029-6","url":null,"abstract":"<div><p>In this paper we answer questions of Arhangel'skii and Michael by providing an example of a regular symmetrizable space which is not subparacompact and has a closed subset which is not a <em>G</em><sub>σ</sub>-set. We also use the idea of sequential order to obtain some positive results, and several examples are provided which show that these results are in some sense the best possible.</p></div>","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"9 3","pages":"Pages 253-261"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-660X(78)90029-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91638696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90031-4
Ann Petrus
{"title":"Contractibility of Whitney continua in C(X)","authors":"Ann Petrus","doi":"10.1016/0016-660X(78)90031-4","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90031-4","url":null,"abstract":"","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"55 1","pages":"275-288"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87728925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90028-4
James R. Boone
{"title":"Pseudo-open functions are monotonic decreasing for ordinal and cardinal invariants","authors":"James R. Boone","doi":"10.1016/0016-660X(78)90028-4","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90028-4","url":null,"abstract":"","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"39 7","pages":"243-251"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72588011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90029-6
S. W. Davis, G. Gruenhage, P. Nyikos
{"title":"Gσ-sets in symmetrizable and related spaces","authors":"S. W. Davis, G. Gruenhage, P. Nyikos","doi":"10.1016/0016-660X(78)90029-6","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90029-6","url":null,"abstract":"","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"40 1","pages":"253-261"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89945810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90030-2
I. Juhász, W. Weiss
{"title":"Martin's axiom and normality","authors":"I. Juhász, W. Weiss","doi":"10.1016/0016-660X(78)90030-2","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90030-2","url":null,"abstract":"","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"11 1","pages":"263-274"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78897284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90031-4
Ann Petrus
We show that there are Whitney maps on the 2-cell such that Whitney continua in the hyperspace of the 2-cell are non-contractible, non-locally contractible, and have non-trivial Čhech cohomology in dimension 2. This implies that contractibility, local contractibility, being an AR, being an ANR, and acyclicity in Čech cohomology are not Whitney properties. We show, however, that contractibility is a Whitney property for the class of dendrites.
{"title":"Contractibility of Whitney continua in C(X)","authors":"Ann Petrus","doi":"10.1016/0016-660X(78)90031-4","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90031-4","url":null,"abstract":"<div><p>We show that there are Whitney maps on the 2-cell such that Whitney continua in the hyperspace of the 2-cell are non-contractible, non-locally contractible, and have non-trivial Čhech cohomology in dimension 2. This implies that contractibility, local contractibility, being an AR, being an ANR, and acyclicity in Čech cohomology are not Whitney properties. We show, however, that contractibility is a Whitney property for the class of dendrites.</p></div>","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"9 3","pages":"Pages 275-288"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-660X(78)90031-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91639160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90027-2
S. S. Khurana
{"title":"A completeness property of some function spaces","authors":"S. S. Khurana","doi":"10.1016/0016-660X(78)90027-2","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90027-2","url":null,"abstract":"","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"9 1","pages":"239-241"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74927628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90026-0
B. Morrel, J. Nagata
{"title":"Statistical metric spaces as related to topological spaces","authors":"B. Morrel, J. Nagata","doi":"10.1016/0016-660X(78)90026-0","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90026-0","url":null,"abstract":"","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"115 1","pages":"233-237"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78274338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-11-01DOI: 10.1016/0016-660X(78)90024-7
M. Ismail
{"title":"A note on a theorem of arhangel'skiǐ","authors":"M. Ismail","doi":"10.1016/0016-660X(78)90024-7","DOIUrl":"https://doi.org/10.1016/0016-660X(78)90024-7","url":null,"abstract":"","PeriodicalId":100574,"journal":{"name":"General Topology and its Applications","volume":"1 1","pages":"217-220"},"PeriodicalIF":0.0,"publicationDate":"1978-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90320010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}