Description: The value of the Hartogs function at a set X is weakly dominated by ~P ( X X. X ) . This follows from a more precise analysis of the bound used in hartogs to prove that ( harX ) is an ordinal. (Contributed by Mario Carneiro, 15-May-2015)
Ref | Expression | ||
---|---|---|---|
Assertion | harwdom | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqid | |
|
2 | eqid | |
|
3 | 1 2 | hartogslem1 | |
4 | 3 | simp2i | |
5 | 3 | simp1i | |
6 | sqxpexg | |
|
7 | 6 | pwexd | |
8 | ssexg | |
|
9 | 5 7 8 | sylancr | |
10 | funex | |
|
11 | 4 9 10 | sylancr | |
12 | funfn | |
|
13 | 4 12 | mpbi | |
14 | 13 | a1i | |
15 | 3 | simp3i | |
16 | harval | |
|
17 | 15 16 | eqtr4d | |
18 | df-fo | |
|
19 | 14 17 18 | sylanbrc | |
20 | fowdom | |
|
21 | 11 19 20 | syl2anc | |
22 | ssdomg | |
|
23 | 7 5 22 | mpisyl | |
24 | domwdom | |
|
25 | 23 24 | syl | |
26 | wdomtr | |
|
27 | 21 25 26 | syl2anc | |