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Type | Label | Description |
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Statement | ||
Theorem | r1rankidb 9801 | Any set is a subset of the hierarchy of its rank. (Contributed by Mario Carneiro, 3-Jun-2013.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β π΄ β (π 1β(rankβπ΄))) | ||
Theorem | r1elssi 9802 | The range of the π 1 function is transitive. Lemma 2.10 of [Kunen] p. 97. One direction of r1elss 9803 that doesn't need π΄ to be a set. (Contributed by Mario Carneiro, 22-Mar-2013.) (Revised by Mario Carneiro, 16-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β π΄ β βͺ (π 1 β On)) | ||
Theorem | r1elss 9803 | The range of the π 1 function is transitive. Lemma 2.10 of [Kunen] p. 97. (Contributed by Mario Carneiro, 22-Mar-2013.) (Revised by Mario Carneiro, 16-Nov-2014.) |
β’ π΄ β V β β’ (π΄ β βͺ (π 1 β On) β π΄ β βͺ (π 1 β On)) | ||
Theorem | pwwf 9804 | A power set is well-founded iff the base set is. (Contributed by Mario Carneiro, 8-Jun-2013.) (Revised by Mario Carneiro, 16-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β π« π΄ β βͺ (π 1 β On)) | ||
Theorem | sswf 9805 | A subset of a well-founded set is well-founded. (Contributed by Mario Carneiro, 17-Nov-2014.) |
β’ ((π΄ β βͺ (π 1 β On) β§ π΅ β π΄) β π΅ β βͺ (π 1 β On)) | ||
Theorem | snwf 9806 | A singleton is well-founded if its element is. (Contributed by Mario Carneiro, 10-Jun-2013.) (Revised by Mario Carneiro, 16-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β {π΄} β βͺ (π 1 β On)) | ||
Theorem | unwf 9807 | A binary union is well-founded iff its elements are. (Contributed by Mario Carneiro, 10-Jun-2013.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ ((π΄ β βͺ (π 1 β On) β§ π΅ β βͺ (π 1 β On)) β (π΄ βͺ π΅) β βͺ (π 1 β On)) | ||
Theorem | prwf 9808 | An unordered pair is well-founded if its elements are. (Contributed by Mario Carneiro, 10-Jun-2013.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ ((π΄ β βͺ (π 1 β On) β§ π΅ β βͺ (π 1 β On)) β {π΄, π΅} β βͺ (π 1 β On)) | ||
Theorem | opwf 9809 | An ordered pair is well-founded if its elements are. (Contributed by Mario Carneiro, 10-Jun-2013.) |
β’ ((π΄ β βͺ (π 1 β On) β§ π΅ β βͺ (π 1 β On)) β β¨π΄, π΅β© β βͺ (π 1 β On)) | ||
Theorem | unir1 9810 | The cumulative hierarchy of sets covers the universe. Proposition 4.45 (b) to (a) of [Mendelson] p. 281. (Contributed by NM, 27-Sep-2004.) (Revised by Mario Carneiro, 8-Jun-2013.) |
β’ βͺ (π 1 β On) = V | ||
Theorem | jech9.3 9811 | Every set belongs to some value of the cumulative hierarchy of sets function π 1, i.e. the indexed union of all values of π 1 is the universe. Lemma 9.3 of [Jech] p. 71. (Contributed by NM, 4-Oct-2003.) (Revised by Mario Carneiro, 8-Jun-2013.) |
β’ βͺ π₯ β On (π 1βπ₯) = V | ||
Theorem | rankwflem 9812* | Every set is well-founded, assuming the Axiom of Regularity. Proposition 9.13 of [TakeutiZaring] p. 78. This variant of tz9.13g 9789 is useful in proofs of theorems about the rank function. (Contributed by NM, 4-Oct-2003.) |
β’ (π΄ β π β βπ₯ β On π΄ β (π 1βsuc π₯)) | ||
Theorem | rankval 9813* | Value of the rank function. Definition 9.14 of [TakeutiZaring] p. 79 (proved as a theorem from our definition). (Contributed by NM, 24-Sep-2003.) (Revised by Mario Carneiro, 10-Sep-2013.) |
β’ π΄ β V β β’ (rankβπ΄) = β© {π₯ β On β£ π΄ β (π 1βsuc π₯)} | ||
Theorem | rankvalg 9814* | Value of the rank function. Definition 9.14 of [TakeutiZaring] p. 79 (proved as a theorem from our definition). This variant of rankval 9813 expresses the class existence requirement as an antecedent instead of a hypothesis. (Contributed by NM, 5-Oct-2003.) |
β’ (π΄ β π β (rankβπ΄) = β© {π₯ β On β£ π΄ β (π 1βsuc π₯)}) | ||
Theorem | rankval2 9815* | Value of an alternate definition of the rank function. Definition of [BellMachover] p. 478. (Contributed by NM, 8-Oct-2003.) |
β’ (π΄ β π΅ β (rankβπ΄) = β© {π₯ β On β£ π΄ β (π 1βπ₯)}) | ||
Theorem | uniwf 9816 | A union is well-founded iff the base set is. (Contributed by Mario Carneiro, 8-Jun-2013.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β βͺ π΄ β βͺ (π 1 β On)) | ||
Theorem | rankr1clem 9817 | Lemma for rankr1c 9818. (Contributed by NM, 6-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ ((π΄ β βͺ (π 1 β On) β§ π΅ β dom π 1) β (Β¬ π΄ β (π 1βπ΅) β π΅ β (rankβπ΄))) | ||
Theorem | rankr1c 9818 | A relationship between the rank function and the cumulative hierarchy of sets function π 1. Proposition 9.15(2) of [TakeutiZaring] p. 79. (Contributed by Mario Carneiro, 22-Mar-2013.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β (π΅ = (rankβπ΄) β (Β¬ π΄ β (π 1βπ΅) β§ π΄ β (π 1βsuc π΅)))) | ||
Theorem | rankidn 9819 | A relationship between the rank function and the cumulative hierarchy of sets function π 1. (Contributed by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β Β¬ π΄ β (π 1β(rankβπ΄))) | ||
Theorem | rankpwi 9820 | The rank of a power set. Part of Exercise 30 of [Enderton] p. 207. (Contributed by Mario Carneiro, 3-Jun-2013.) |
β’ (π΄ β βͺ (π 1 β On) β (rankβπ« π΄) = suc (rankβπ΄)) | ||
Theorem | rankelb 9821 | The membership relation is inherited by the rank function. Proposition 9.16 of [TakeutiZaring] p. 79. (Contributed by NM, 4-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΅ β βͺ (π 1 β On) β (π΄ β π΅ β (rankβπ΄) β (rankβπ΅))) | ||
Theorem | wfelirr 9822 | A well-founded set is not a member of itself. This proof does not require the axiom of regularity, unlike elirr 9594. (Contributed by Mario Carneiro, 2-Jan-2017.) |
β’ (π΄ β βͺ (π 1 β On) β Β¬ π΄ β π΄) | ||
Theorem | rankval3b 9823* | The value of the rank function expressed recursively: the rank of a set is the smallest ordinal number containing the ranks of all members of the set. Proposition 9.17 of [TakeutiZaring] p. 79. (Contributed by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β (rankβπ΄) = β© {π₯ β On β£ βπ¦ β π΄ (rankβπ¦) β π₯}) | ||
Theorem | ranksnb 9824 | The rank of a singleton. Theorem 15.17(v) of [Monk1] p. 112. (Contributed by Mario Carneiro, 10-Jun-2013.) |
β’ (π΄ β βͺ (π 1 β On) β (rankβ{π΄}) = suc (rankβπ΄)) | ||
Theorem | rankonidlem 9825 | Lemma for rankonid 9826. (Contributed by NM, 14-Oct-2003.) (Revised by Mario Carneiro, 22-Mar-2013.) |
β’ (π΄ β dom π 1 β (π΄ β βͺ (π 1 β On) β§ (rankβπ΄) = π΄)) | ||
Theorem | rankonid 9826 | The rank of an ordinal number is itself. Proposition 9.18 of [TakeutiZaring] p. 79 and its converse. (Contributed by NM, 14-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β dom π 1 β (rankβπ΄) = π΄) | ||
Theorem | onwf 9827 | The ordinals are all well-founded. (Contributed by Mario Carneiro, 22-Mar-2013.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ On β βͺ (π 1 β On) | ||
Theorem | onssr1 9828 | Initial segments of the ordinals are contained in initial segments of the cumulative hierarchy. (Contributed by FL, 20-Apr-2011.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β dom π 1 β π΄ β (π 1βπ΄)) | ||
Theorem | rankr1g 9829 | A relationship between the rank function and the cumulative hierarchy of sets function π 1. Proposition 9.15(2) of [TakeutiZaring] p. 79. (Contributed by NM, 6-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β π β (π΅ = (rankβπ΄) β (Β¬ π΄ β (π 1βπ΅) β§ π΄ β (π 1βsuc π΅)))) | ||
Theorem | rankid 9830 | Identity law for the rank function. (Contributed by NM, 3-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ π΄ β (π 1βsuc (rankβπ΄)) | ||
Theorem | rankr1 9831 | A relationship between the rank function and the cumulative hierarchy of sets function π 1. Proposition 9.15(2) of [TakeutiZaring] p. 79. (Contributed by NM, 6-Oct-2003.) (Proof shortened by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ (π΅ = (rankβπ΄) β (Β¬ π΄ β (π 1βπ΅) β§ π΄ β (π 1βsuc π΅))) | ||
Theorem | ssrankr1 9832 | A relationship between an ordinal number less than or equal to a rank, and the cumulative hierarchy of sets π 1. Proposition 9.15(3) of [TakeutiZaring] p. 79. (Contributed by NM, 8-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ (π΅ β On β (π΅ β (rankβπ΄) β Β¬ π΄ β (π 1βπ΅))) | ||
Theorem | rankr1a 9833 | A relationship between rank and π 1, clearly equivalent to ssrankr1 9832 and friends through trichotomy, but in Raph's opinion considerably more intuitive. See rankr1b 9861 for the subset version. (Contributed by Raph Levien, 29-May-2004.) |
β’ π΄ β V β β’ (π΅ β On β (π΄ β (π 1βπ΅) β (rankβπ΄) β π΅)) | ||
Theorem | r1val2 9834* | The value of the cumulative hierarchy of sets function expressed in terms of rank. Definition 15.19 of [Monk1] p. 113. (Contributed by NM, 30-Nov-2003.) |
β’ (π΄ β On β (π 1βπ΄) = {π₯ β£ (rankβπ₯) β π΄}) | ||
Theorem | r1val3 9835* | The value of the cumulative hierarchy of sets function expressed in terms of rank. Theorem 15.18 of [Monk1] p. 113. (Contributed by NM, 30-Nov-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β On β (π 1βπ΄) = βͺ π₯ β π΄ π« {π¦ β£ (rankβπ¦) β π₯}) | ||
Theorem | rankel 9836 | The membership relation is inherited by the rank function. Proposition 9.16 of [TakeutiZaring] p. 79. (Contributed by NM, 4-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΅ β V β β’ (π΄ β π΅ β (rankβπ΄) β (rankβπ΅)) | ||
Theorem | rankval3 9837* | The value of the rank function expressed recursively: the rank of a set is the smallest ordinal number containing the ranks of all members of the set. Proposition 9.17 of [TakeutiZaring] p. 79. (Contributed by NM, 11-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ (rankβπ΄) = β© {π₯ β On β£ βπ¦ β π΄ (rankβπ¦) β π₯} | ||
Theorem | bndrank 9838* | Any class whose elements have bounded rank is a set. Proposition 9.19 of [TakeutiZaring] p. 80. (Contributed by NM, 13-Oct-2003.) |
β’ (βπ₯ β On βπ¦ β π΄ (rankβπ¦) β π₯ β π΄ β V) | ||
Theorem | unbndrank 9839* | The elements of a proper class have unbounded rank. Exercise 2 of [TakeutiZaring] p. 80. (Contributed by NM, 13-Oct-2003.) |
β’ (Β¬ π΄ β V β βπ₯ β On βπ¦ β π΄ π₯ β (rankβπ¦)) | ||
Theorem | rankpw 9840 | The rank of a power set. Part of Exercise 30 of [Enderton] p. 207. (Contributed by NM, 22-Nov-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ (rankβπ« π΄) = suc (rankβπ΄) | ||
Theorem | ranklim 9841 | The rank of a set belongs to a limit ordinal iff the rank of its power set does. (Contributed by NM, 18-Sep-2006.) |
β’ (Lim π΅ β ((rankβπ΄) β π΅ β (rankβπ« π΄) β π΅)) | ||
Theorem | r1pw 9842 | A stronger property of π 1 than rankpw 9840. The latter merely proves that π 1 of the successor is a power set, but here we prove that if π΄ is in the cumulative hierarchy, then π« π΄ is in the cumulative hierarchy of the successor. (Contributed by Raph Levien, 29-May-2004.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΅ β On β (π΄ β (π 1βπ΅) β π« π΄ β (π 1βsuc π΅))) | ||
Theorem | r1pwALT 9843 | Alternate shorter proof of r1pw 9842 based on the additional axioms ax-reg 9589 and ax-inf2 9638. (Contributed by Raph Levien, 29-May-2004.) (Proof modification is discouraged.) (New usage is discouraged.) |
β’ (π΅ β On β (π΄ β (π 1βπ΅) β π« π΄ β (π 1βsuc π΅))) | ||
Theorem | r1pwcl 9844 | The cumulative hierarchy of a limit ordinal is closed under power set. (Contributed by Raph Levien, 29-May-2004.) (Proof shortened by Mario Carneiro, 17-Nov-2014.) |
β’ (Lim π΅ β (π΄ β (π 1βπ΅) β π« π΄ β (π 1βπ΅))) | ||
Theorem | rankssb 9845 | The subset relation is inherited by the rank function. Exercise 1 of [TakeutiZaring] p. 80. (Contributed by NM, 25-Nov-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΅ β βͺ (π 1 β On) β (π΄ β π΅ β (rankβπ΄) β (rankβπ΅))) | ||
Theorem | rankss 9846 | The subset relation is inherited by the rank function. Exercise 1 of [TakeutiZaring] p. 80. (Contributed by NM, 25-Nov-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΅ β V β β’ (π΄ β π΅ β (rankβπ΄) β (rankβπ΅)) | ||
Theorem | rankunb 9847 | The rank of the union of two sets. Theorem 15.17(iii) of [Monk1] p. 112. (Contributed by Mario Carneiro, 10-Jun-2013.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ ((π΄ β βͺ (π 1 β On) β§ π΅ β βͺ (π 1 β On)) β (rankβ(π΄ βͺ π΅)) = ((rankβπ΄) βͺ (rankβπ΅))) | ||
Theorem | rankprb 9848 | The rank of an unordered pair. Part of Exercise 30 of [Enderton] p. 207. (Contributed by Mario Carneiro, 10-Jun-2013.) |
β’ ((π΄ β βͺ (π 1 β On) β§ π΅ β βͺ (π 1 β On)) β (rankβ{π΄, π΅}) = suc ((rankβπ΄) βͺ (rankβπ΅))) | ||
Theorem | rankopb 9849 | The rank of an ordered pair. Part of Exercise 4 of [Kunen] p. 107. (Contributed by Mario Carneiro, 10-Jun-2013.) |
β’ ((π΄ β βͺ (π 1 β On) β§ π΅ β βͺ (π 1 β On)) β (rankββ¨π΄, π΅β©) = suc suc ((rankβπ΄) βͺ (rankβπ΅))) | ||
Theorem | rankuni2b 9850* | The value of the rank function expressed recursively: the rank of a set is the smallest ordinal number containing the ranks of all members of the set. Proposition 9.17 of [TakeutiZaring] p. 79. (Contributed by Mario Carneiro, 8-Jun-2013.) |
β’ (π΄ β βͺ (π 1 β On) β (rankββͺ π΄) = βͺ π₯ β π΄ (rankβπ₯)) | ||
Theorem | ranksn 9851 | The rank of a singleton. Theorem 15.17(v) of [Monk1] p. 112. (Contributed by NM, 28-Nov-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ (rankβ{π΄}) = suc (rankβπ΄) | ||
Theorem | rankuni2 9852* | The rank of a union. Part of Theorem 15.17(iv) of [Monk1] p. 112. (Contributed by NM, 30-Nov-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ (rankββͺ π΄) = βͺ π₯ β π΄ (rankβπ₯) | ||
Theorem | rankun 9853 | The rank of the union of two sets. Theorem 15.17(iii) of [Monk1] p. 112. (Contributed by NM, 26-Nov-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V & β’ π΅ β V β β’ (rankβ(π΄ βͺ π΅)) = ((rankβπ΄) βͺ (rankβπ΅)) | ||
Theorem | rankpr 9854 | The rank of an unordered pair. Part of Exercise 30 of [Enderton] p. 207. (Contributed by NM, 28-Nov-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V & β’ π΅ β V β β’ (rankβ{π΄, π΅}) = suc ((rankβπ΄) βͺ (rankβπ΅)) | ||
Theorem | rankop 9855 | The rank of an ordered pair. Part of Exercise 4 of [Kunen] p. 107. (Contributed by NM, 13-Sep-2006.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V & β’ π΅ β V β β’ (rankββ¨π΄, π΅β©) = suc suc ((rankβπ΄) βͺ (rankβπ΅)) | ||
Theorem | r1rankid 9856 | Any set is a subset of the hierarchy of its rank. (Contributed by NM, 14-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β π β π΄ β (π 1β(rankβπ΄))) | ||
Theorem | rankeq0b 9857 | A set is empty iff its rank is empty. (Contributed by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β βͺ (π 1 β On) β (π΄ = β β (rankβπ΄) = β )) | ||
Theorem | rankeq0 9858 | A set is empty iff its rank is empty. (Contributed by NM, 18-Sep-2006.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ (π΄ = β β (rankβπ΄) = β ) | ||
Theorem | rankr1id 9859 | The rank of the hierarchy of an ordinal number is itself. (Contributed by NM, 14-Oct-2003.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (π΄ β dom π 1 β (rankβ(π 1βπ΄)) = π΄) | ||
Theorem | rankuni 9860 | The rank of a union. Part of Exercise 4 of [Kunen] p. 107. (Contributed by NM, 15-Sep-2006.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ (rankββͺ π΄) = βͺ (rankβπ΄) | ||
Theorem | rankr1b 9861 | A relationship between rank and π 1. See rankr1a 9833 for the membership version. (Contributed by NM, 15-Sep-2006.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V β β’ (π΅ β On β (π΄ β (π 1βπ΅) β (rankβπ΄) β π΅)) | ||
Theorem | ranksuc 9862 | The rank of a successor. (Contributed by NM, 18-Sep-2006.) |
β’ π΄ β V β β’ (rankβsuc π΄) = suc (rankβπ΄) | ||
Theorem | rankuniss 9863 | Upper bound of the rank of a union. Part of Exercise 30 of [Enderton] p. 207. (Contributed by NM, 30-Nov-2003.) |
β’ π΄ β V β β’ (rankββͺ π΄) β (rankβπ΄) | ||
Theorem | rankval4 9864* | The rank of a set is the supremum of the successors of the ranks of its members. Exercise 9.1 of [Jech] p. 72. Also a special case of Theorem 7V(b) of [Enderton] p. 204. (Contributed by NM, 12-Oct-2003.) |
β’ π΄ β V β β’ (rankβπ΄) = βͺ π₯ β π΄ suc (rankβπ₯) | ||
Theorem | rankbnd 9865* | The rank of a set is bounded by a bound for the successor of its members. (Contributed by NM, 18-Sep-2006.) |
β’ π΄ β V β β’ (βπ₯ β π΄ suc (rankβπ₯) β π΅ β (rankβπ΄) β π΅) | ||
Theorem | rankbnd2 9866* | The rank of a set is bounded by the successor of a bound for its members. (Contributed by NM, 15-Sep-2006.) |
β’ π΄ β V β β’ (π΅ β On β (βπ₯ β π΄ (rankβπ₯) β π΅ β (rankβπ΄) β suc π΅)) | ||
Theorem | rankc1 9867* | A relationship that can be used for computation of rank. (Contributed by NM, 16-Sep-2006.) |
β’ π΄ β V β β’ (βπ₯ β π΄ (rankβπ₯) β (rankββͺ π΄) β (rankβπ΄) = (rankββͺ π΄)) | ||
Theorem | rankc2 9868* | A relationship that can be used for computation of rank. (Contributed by NM, 16-Sep-2006.) |
β’ π΄ β V β β’ (βπ₯ β π΄ (rankβπ₯) = (rankββͺ π΄) β (rankβπ΄) = suc (rankββͺ π΄)) | ||
Theorem | rankelun 9869 | Rank membership is inherited by union. (Contributed by NM, 18-Sep-2006.) (Proof shortened by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V & β’ π΅ β V & β’ πΆ β V & β’ π· β V β β’ (((rankβπ΄) β (rankβπΆ) β§ (rankβπ΅) β (rankβπ·)) β (rankβ(π΄ βͺ π΅)) β (rankβ(πΆ βͺ π·))) | ||
Theorem | rankelpr 9870 | Rank membership is inherited by unordered pairs. (Contributed by NM, 18-Sep-2006.) (Revised by Mario Carneiro, 17-Nov-2014.) |
β’ π΄ β V & β’ π΅ β V & β’ πΆ β V & β’ π· β V β β’ (((rankβπ΄) β (rankβπΆ) β§ (rankβπ΅) β (rankβπ·)) β (rankβ{π΄, π΅}) β (rankβ{πΆ, π·})) | ||
Theorem | rankelop 9871 | Rank membership is inherited by ordered pairs. (Contributed by NM, 18-Sep-2006.) |
β’ π΄ β V & β’ π΅ β V & β’ πΆ β V & β’ π· β V β β’ (((rankβπ΄) β (rankβπΆ) β§ (rankβπ΅) β (rankβπ·)) β (rankββ¨π΄, π΅β©) β (rankββ¨πΆ, π·β©)) | ||
Theorem | rankxpl 9872 | A lower bound on the rank of a Cartesian product. (Contributed by NM, 18-Sep-2006.) |
β’ π΄ β V & β’ π΅ β V β β’ ((π΄ Γ π΅) β β β (rankβ(π΄ βͺ π΅)) β (rankβ(π΄ Γ π΅))) | ||
Theorem | rankxpu 9873 | An upper bound on the rank of a Cartesian product. (Contributed by NM, 18-Sep-2006.) |
β’ π΄ β V & β’ π΅ β V β β’ (rankβ(π΄ Γ π΅)) β suc suc (rankβ(π΄ βͺ π΅)) | ||
Theorem | rankfu 9874 | An upper bound on the rank of a function. (Contributed by GΓ©rard Lang, 5-Aug-2018.) |
β’ π΄ β V & β’ π΅ β V β β’ (πΉ:π΄βΆπ΅ β (rankβπΉ) β suc suc (rankβ(π΄ βͺ π΅))) | ||
Theorem | rankmapu 9875 | An upper bound on the rank of set exponentiation. (Contributed by GΓ©rard Lang, 5-Aug-2018.) |
β’ π΄ β V & β’ π΅ β V β β’ (rankβ(π΄ βm π΅)) β suc suc suc (rankβ(π΄ βͺ π΅)) | ||
Theorem | rankxplim 9876 | The rank of a Cartesian product when the rank of the union of its arguments is a limit ordinal. Part of Exercise 4 of [Kunen] p. 107. See rankxpsuc 9879 for the successor case. (Contributed by NM, 19-Sep-2006.) |
β’ π΄ β V & β’ π΅ β V β β’ ((Lim (rankβ(π΄ βͺ π΅)) β§ (π΄ Γ π΅) β β ) β (rankβ(π΄ Γ π΅)) = (rankβ(π΄ βͺ π΅))) | ||
Theorem | rankxplim2 9877 | If the rank of a Cartesian product is a limit ordinal, so is the rank of the union of its arguments. (Contributed by NM, 19-Sep-2006.) |
β’ π΄ β V & β’ π΅ β V β β’ (Lim (rankβ(π΄ Γ π΅)) β Lim (rankβ(π΄ βͺ π΅))) | ||
Theorem | rankxplim3 9878 | The rank of a Cartesian product is a limit ordinal iff its union is. (Contributed by NM, 19-Sep-2006.) |
β’ π΄ β V & β’ π΅ β V β β’ (Lim (rankβ(π΄ Γ π΅)) β Lim βͺ (rankβ(π΄ Γ π΅))) | ||
Theorem | rankxpsuc 9879 | The rank of a Cartesian product when the rank of the union of its arguments is a successor ordinal. Part of Exercise 4 of [Kunen] p. 107. See rankxplim 9876 for the limit ordinal case. (Contributed by NM, 19-Sep-2006.) |
β’ π΄ β V & β’ π΅ β V β β’ (((rankβ(π΄ βͺ π΅)) = suc πΆ β§ (π΄ Γ π΅) β β ) β (rankβ(π΄ Γ π΅)) = suc suc (rankβ(π΄ βͺ π΅))) | ||
Theorem | tcwf 9880 | The transitive closure function is well-founded if its argument is. (Contributed by Mario Carneiro, 23-Jun-2013.) |
β’ (π΄ β βͺ (π 1 β On) β (TCβπ΄) β βͺ (π 1 β On)) | ||
Theorem | tcrank 9881 | This theorem expresses two different facts from the two subset implications in this equality. In the forward direction, it says that the transitive closure has members of every rank below π΄. Stated another way, to construct a set at a given rank, you have to climb the entire hierarchy of ordinals below (rankβπ΄), constructing at least one set at each level in order to move up the ranks. In the reverse direction, it says that every member of (TCβπ΄) has a rank below the rank of π΄, since intuitively it contains only the members of π΄ and the members of those and so on, but nothing "bigger" than π΄. (Contributed by Mario Carneiro, 23-Jun-2013.) |
β’ (π΄ β βͺ (π 1 β On) β (rankβπ΄) = (rank β (TCβπ΄))) | ||
Theorem | scottex 9882* | Scott's trick collects all sets that have a certain property and are of the smallest possible rank. This theorem shows that the resulting collection, expressed as in Equation 9.3 of [Jech] p. 72, is a set. (Contributed by NM, 13-Oct-2003.) |
β’ {π₯ β π΄ β£ βπ¦ β π΄ (rankβπ₯) β (rankβπ¦)} β V | ||
Theorem | scott0 9883* | Scott's trick collects all sets that have a certain property and are of the smallest possible rank. This theorem shows that the resulting collection, expressed as in Equation 9.3 of [Jech] p. 72, contains at least one representative with the property, if there is one. In other words, the collection is empty iff no set has the property (i.e. π΄ is empty). (Contributed by NM, 15-Oct-2003.) |
β’ (π΄ = β β {π₯ β π΄ β£ βπ¦ β π΄ (rankβπ₯) β (rankβπ¦)} = β ) | ||
Theorem | scottexs 9884* | Theorem scheme version of scottex 9882. The collection of all π₯ of minimum rank such that π(π₯) is true, is a set. (Contributed by NM, 13-Oct-2003.) |
β’ {π₯ β£ (π β§ βπ¦([π¦ / π₯]π β (rankβπ₯) β (rankβπ¦)))} β V | ||
Theorem | scott0s 9885* | Theorem scheme version of scott0 9883. The collection of all π₯ of minimum rank such that π(π₯) is true, is not empty iff there is an π₯ such that π(π₯) holds. (Contributed by NM, 13-Oct-2003.) |
β’ (βπ₯π β {π₯ β£ (π β§ βπ¦([π¦ / π₯]π β (rankβπ₯) β (rankβπ¦)))} β β ) | ||
Theorem | cplem1 9886* | Lemma for the Collection Principle cp 9888. (Contributed by NM, 17-Oct-2003.) |
β’ πΆ = {π¦ β π΅ β£ βπ§ β π΅ (rankβπ¦) β (rankβπ§)} & β’ π· = βͺ π₯ β π΄ πΆ β β’ βπ₯ β π΄ (π΅ β β β (π΅ β© π·) β β ) | ||
Theorem | cplem2 9887* | Lemma for the Collection Principle cp 9888. (Contributed by NM, 17-Oct-2003.) |
β’ π΄ β V β β’ βπ¦βπ₯ β π΄ (π΅ β β β (π΅ β© π¦) β β ) | ||
Theorem | cp 9888* | Collection Principle. This remarkable theorem scheme is in effect a very strong generalization of the Axiom of Replacement. The proof makes use of Scott's trick scottex 9882 that collapses a proper class into a set of minimum rank. The wff π can be thought of as π(π₯, π¦). Scheme "Collection Principle" of [Jech] p. 72. (Contributed by NM, 17-Oct-2003.) |
β’ βπ€βπ₯ β π§ (βπ¦π β βπ¦ β π€ π) | ||
Theorem | bnd 9889* | A very strong generalization of the Axiom of Replacement (compare zfrep6 7943), derived from the Collection Principle cp 9888. Its strength lies in the rather profound fact that π(π₯, π¦) does not have to be a "function-like" wff, as it does in the standard Axiom of Replacement. This theorem is sometimes called the Boundedness Axiom. (Contributed by NM, 17-Oct-2004.) |
β’ (βπ₯ β π§ βπ¦π β βπ€βπ₯ β π§ βπ¦ β π€ π) | ||
Theorem | bnd2 9890* | A variant of the Boundedness Axiom bnd 9889 that picks a subset π§ out of a possibly proper class π΅ in which a property is true. (Contributed by NM, 4-Feb-2004.) |
β’ π΄ β V β β’ (βπ₯ β π΄ βπ¦ β π΅ π β βπ§(π§ β π΅ β§ βπ₯ β π΄ βπ¦ β π§ π)) | ||
Theorem | kardex 9891* | The collection of all sets equinumerous to a set π΄ and having the least possible rank is a set. This is the part of the justification of the definition of kard of [Enderton] p. 222. (Contributed by NM, 14-Dec-2003.) |
β’ {π₯ β£ (π₯ β π΄ β§ βπ¦(π¦ β π΄ β (rankβπ₯) β (rankβπ¦)))} β V | ||
Theorem | karden 9892* | If we allow the Axiom of Regularity, we can avoid the Axiom of Choice by defining the cardinal number of a set as the set of all sets equinumerous to it and having the least possible rank. This theorem proves the equinumerosity relationship for this definition (compare carden 10548). The hypotheses correspond to the definition of kard of [Enderton] p. 222 (which we don't define separately since currently we do not use it elsewhere). This theorem along with kardex 9891 justify the definition of kard. The restriction to the least rank prevents the proper class that would result from {π₯ β£ π₯ β π΄}. (Contributed by NM, 18-Dec-2003.) (Revised by AV, 12-Jul-2022.) |
β’ π΄ β V & β’ πΆ = {π₯ β£ (π₯ β π΄ β§ βπ¦(π¦ β π΄ β (rankβπ₯) β (rankβπ¦)))} & β’ π· = {π₯ β£ (π₯ β π΅ β§ βπ¦(π¦ β π΅ β (rankβπ₯) β (rankβπ¦)))} β β’ (πΆ = π· β π΄ β π΅) | ||
Theorem | htalem 9893* | Lemma for defining an emulation of Hilbert's epsilon. Hilbert's epsilon is described at http://plato.stanford.edu/entries/epsilon-calculus/. This theorem is equivalent to Hilbert's "transfinite axiom", described on that page, with the additional π We π΄ antecedent. The element π΅ is the epsilon that the theorem emulates. (Contributed by NM, 11-Mar-2004.) (Revised by Mario Carneiro, 25-Jun-2015.) |
β’ π΄ β V & β’ π΅ = (β©π₯ β π΄ βπ¦ β π΄ Β¬ π¦π π₯) β β’ ((π We π΄ β§ π΄ β β ) β π΅ β π΄) | ||
Theorem | hta 9894* |
A ZFC emulation of Hilbert's transfinite axiom. The set π΅ has the
properties of Hilbert's epsilon, except that it also depends on a
well-ordering π
. This theorem arose from
discussions with Raph
Levien on 5-Mar-2004 about translating the HOL proof language, which
uses Hilbert's epsilon. See
https://us.metamath.org/downloads/choice.txt
(copy of obsolete link
http://ghilbert.org/choice.txt) and
https://us.metamath.org/downloads/megillaward2005he.pdf.
Hilbert's epsilon is described at http://plato.stanford.edu/entries/epsilon-calculus/. This theorem differs from Hilbert's transfinite axiom described on that page in that it requires π We π΄ as an antecedent. Class π΄ collects the sets of the least rank for which π(π₯) is true. Class π΅, which emulates Hilbert's epsilon, is the minimum element in a well-ordering π on π΄. If a well-ordering π on π΄ can be expressed in a closed form, as might be the case if we are working with say natural numbers, we can eliminate the antecedent with modus ponens, giving us the exact equivalent of Hilbert's transfinite axiom. Otherwise, we replace π with a dummy setvar variable, say π€, and attach π€ We π΄ as an antecedent in each step of the ZFC version of the HOL proof until the epsilon is eliminated. At that point, π΅ (which will have π€ as a free variable) will no longer be present, and we can eliminate π€ We π΄ by applying exlimiv 1933 and weth 10492, using scottexs 9884 to establish the existence of π΄. For a version of this theorem scheme using class (meta)variables instead of wff (meta)variables, see htalem 9893. (Contributed by NM, 11-Mar-2004.) (Revised by Mario Carneiro, 25-Jun-2015.) |
β’ π΄ = {π₯ β£ (π β§ βπ¦([π¦ / π₯]π β (rankβπ₯) β (rankβπ¦)))} & β’ π΅ = (β©π§ β π΄ βπ€ β π΄ Β¬ π€π π§) β β’ (π We π΄ β (π β [π΅ / π₯]π)) | ||
Syntax | cdju 9895 | Extend class notation to include disjoint union of two classes. |
class (π΄ β π΅) | ||
Syntax | cinl 9896 | Extend class notation to include left injection of a disjoint union. |
class inl | ||
Syntax | cinr 9897 | Extend class notation to include right injection of a disjoint union. |
class inr | ||
Definition | df-dju 9898 | Disjoint union of two classes. This is a way of creating a set which contains elements corresponding to each element of π΄ or π΅, tagging each one with whether it came from π΄ or π΅. (Contributed by Jim Kingdon, 20-Jun-2022.) |
β’ (π΄ β π΅) = (({β } Γ π΄) βͺ ({1o} Γ π΅)) | ||
Definition | df-inl 9899 | Left injection of a disjoint union. (Contributed by Mario Carneiro, 21-Jun-2022.) |
β’ inl = (π₯ β V β¦ β¨β , π₯β©) | ||
Definition | df-inr 9900 | Right injection of a disjoint union. (Contributed by Mario Carneiro, 21-Jun-2022.) |
β’ inr = (π₯ β V β¦ β¨1o, π₯β©) |
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