84:
74:
53:
22:
288:
Nevermind, I was mistaken. "Countably compact" means every countable cover has a finite subcover. "Lindelof" means every cover has a countable subcover. "Compact" means every cover has a finite subcover. It is obvious that a countably compact space is compact if and only if
Lindelof.
247:
I added Jech's book as a reference. This is perhaps overkill, any book on Set Theory will define omega_1. (Kunen, Komjath, Just+Weese, Drake+Singh, Deiser, ...) Also some books in
Algebra and/or Analysis will define omega_1 and at least mention some basic properties.
140:
273:"a countably compact space is compact if and only if it is Lindelöf" I believe that this is only true for T1 spaces, though I don't have a counterexample in mind.
318:
130:
313:
106:
97:
58:
33:
21:
176:
195:
278:
39:
83:
164:
290:
274:
232:
105:
on
Knowledge. If you would like to participate, please visit the project page, where you can join
89:
73:
52:
191:
172:
259:
216:
208:
223:
is not ω. Any continuous function from to the reals must be constant on for some α<ω
228:
183:
298:
282:
263:
236:
307:
168:
187:
255:
102:
220:
79:
251:
I also added "Counterexamples in topology" for the topological properties.
15:
186:
and in my topology reference. I'll go ahead and change it.
101:, a collaborative effort to improve the coverage of
182:I think it is countably compact, and so it says in
8:
19:
47:
49:
7:
95:This article is within the scope of
38:It is of interest to the following
14:
319:Mid-priority mathematics articles
115:Knowledge:WikiProject Mathematics
314:Start-Class mathematics articles
118:Template:WikiProject Mathematics
82:
72:
51:
20:
269:Compact if and only if Lindelof
135:This article has been rated as
1:
109:and see a list of open tasks.
159:"The topological space [0,ω
335:
299:22:33, 5 April 2023 (UTC)
283:00:27, 5 April 2023 (UTC)
134:
67:
46:
264:15:52, 23 May 2011 (UTC)
237:19:09, 6 June 2011 (UTC)
141:project's priority scale
98:WikiProject Mathematics
28:This article is rated
165:sequentially compact
121:mathematics articles
90:Mathematics portal
34:content assessment
177:countably compact
155:
154:
151:
150:
147:
146:
326:
197:
196:
158:
123:
122:
119:
116:
113:
92:
87:
86:
76:
69:
68:
63:
55:
48:
31:
25:
24:
16:
334:
333:
329:
328:
327:
325:
324:
323:
304:
303:
271:
245:
226:
219:, that is, its
217:regular ordinal
214:
209:axiom of choice
162:
120:
117:
114:
111:
110:
88:
81:
61:
32:on Knowledge's
29:
12:
11:
5:
332:
330:
322:
321:
316:
306:
305:
302:
301:
270:
267:
244:
241:
240:
239:
224:
212:
184:Order topology
160:
157:
156:
153:
152:
149:
148:
145:
144:
133:
127:
126:
124:
107:the discussion
94:
93:
77:
65:
64:
56:
44:
43:
37:
26:
13:
10:
9:
6:
4:
3:
2:
331:
320:
317:
315:
312:
311:
309:
300:
296:
292:
287:
286:
285:
284:
280:
276:
268:
266:
265:
261:
257:
252:
249:
242:
238:
234:
230:
222:
218:
211:holds, then ω
210:
206:
205:
204:
202:
200:
198:
193:
189:
185:
180:
178:
174:
170:
166:
142:
138:
132:
129:
128:
125:
108:
104:
100:
99:
91:
85:
80:
78:
75:
71:
70:
66:
60:
57:
54:
50:
45:
41:
35:
27:
23:
18:
17:
272:
253:
250:
246:
203:
201:
199:
181:
137:Mid-priority
136:
96:
62:Mid‑priority
40:WikiProjects
112:Mathematics
103:mathematics
59:Mathematics
30:Start-class
308:Categories
243:References
221:cofinality
171:(nor even
229:JRSpriggs
291:DanRaies
275:DanRaies
173:Lindelöf
167:but not
207:If the
188:YohanN7
169:compact
139:on the
256:Aleph4
36:scale.
215:is a
179:). "
163:) is
295:talk
279:talk
260:talk
233:talk
192:talk
175:or
131:Mid
310::
297:)
281:)
262:)
254:--
235:)
227:.
194:)
293:(
277:(
258:(
231:(
225:1
213:1
190:(
161:1
143:.
42::
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.