Description: The empty intersection in a topology is realized by the base set. (Contributed by Zhi Wang, 30-Sep-2024)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | topclat.i | |- I = ( toInc ` J ) | |
| toplatlub.j | |- ( ph -> J e. Top ) | ||
| toplatglb0.g | |- G = ( glb ` I ) | ||
| Assertion | toplatglb0 | |- ( ph -> ( G ` (/) ) = U. J ) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | topclat.i | |- I = ( toInc ` J ) | |
| 2 | toplatlub.j | |- ( ph -> J e. Top ) | |
| 3 | toplatglb0.g | |- G = ( glb ` I ) | |
| 4 | 3 | a1i | |- ( ph -> G = ( glb ` I ) ) | 
| 5 | eqid | |- U. J = U. J | |
| 6 | 5 | topopn | |- ( J e. Top -> U. J e. J ) | 
| 7 | 2 6 | syl | |- ( ph -> U. J e. J ) | 
| 8 | 1 4 7 | ipoglb0 | |- ( ph -> ( G ` (/) ) = U. J ) |