Theorem mulscut2

Description: Show that the cut involved in surreal multiplication is actually a cut. (Contributed by Scott Fenton, 7-Mar-2025)

	Ref	Expression
Hypotheses	mulscut.1	⊢ ( 𝜑 → 𝐴 ∈ No )
	mulscut.2	⊢ ( 𝜑 → 𝐵 ∈ No )
Assertion	mulscut2	⊢ ( 𝜑 → ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) )

Proof

Step	Hyp	Ref	Expression
1		mulscut.1	⊢ ( 𝜑 → 𝐴 ∈ No )
2		mulscut.2	⊢ ( 𝜑 → 𝐵 ∈ No )
3	1 2	mulscut	⊢ ( 𝜑 → ( ( 𝐴 ·s 𝐵 ) ∈ No ∧ ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s { ( 𝐴 ·s 𝐵 ) } ∧ { ( 𝐴 ·s 𝐵 ) } <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) ) )
4		3anass	⊢ ( ( ( 𝐴 ·s 𝐵 ) ∈ No ∧ ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s { ( 𝐴 ·s 𝐵 ) } ∧ { ( 𝐴 ·s 𝐵 ) } <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) ) ↔ ( ( 𝐴 ·s 𝐵 ) ∈ No ∧ ( ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s { ( 𝐴 ·s 𝐵 ) } ∧ { ( 𝐴 ·s 𝐵 ) } <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) ) ) )
5	3 4	sylib	⊢ ( 𝜑 → ( ( 𝐴 ·s 𝐵 ) ∈ No ∧ ( ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s { ( 𝐴 ·s 𝐵 ) } ∧ { ( 𝐴 ·s 𝐵 ) } <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) ) ) )
6	5	simprd	⊢ ( 𝜑 → ( ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s { ( 𝐴 ·s 𝐵 ) } ∧ { ( 𝐴 ·s 𝐵 ) } <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) ) )
7		ovex	⊢ ( 𝐴 ·s 𝐵 ) ∈ V
8	7	snnz	⊢ { ( 𝐴 ·s 𝐵 ) } ≠ ∅
9		sslttr	⊢ ( ( ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s { ( 𝐴 ·s 𝐵 ) } ∧ { ( 𝐴 ·s 𝐵 ) } <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) ∧ { ( 𝐴 ·s 𝐵 ) } ≠ ∅ ) → ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) )
10	8 9	mp3an3	⊢ ( ( ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s { ( 𝐴 ·s 𝐵 ) } ∧ { ( 𝐴 ·s 𝐵 ) } <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) ) → ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) )
11	6 10	syl	⊢ ( 𝜑 → ( { 𝑎 ∣ ∃ 𝑝 ∈ ( L ‘ 𝐴 ) ∃ 𝑞 ∈ ( L ‘ 𝐵 ) 𝑎 = ( ( ( 𝑝 ·s 𝐵 ) +s ( 𝐴 ·s 𝑞 ) ) -s ( 𝑝 ·s 𝑞 ) ) } ∪ { 𝑏 ∣ ∃ 𝑟 ∈ ( R ‘ 𝐴 ) ∃ 𝑠 ∈ ( R ‘ 𝐵 ) 𝑏 = ( ( ( 𝑟 ·s 𝐵 ) +s ( 𝐴 ·s 𝑠 ) ) -s ( 𝑟 ·s 𝑠 ) ) } ) <<s ( { 𝑐 ∣ ∃ 𝑡 ∈ ( L ‘ 𝐴 ) ∃ 𝑢 ∈ ( R ‘ 𝐵 ) 𝑐 = ( ( ( 𝑡 ·s 𝐵 ) +s ( 𝐴 ·s 𝑢 ) ) -s ( 𝑡 ·s 𝑢 ) ) } ∪ { 𝑑 ∣ ∃ 𝑣 ∈ ( R ‘ 𝐴 ) ∃ 𝑤 ∈ ( L ‘ 𝐵 ) 𝑑 = ( ( ( 𝑣 ·s 𝐵 ) +s ( 𝐴 ·s 𝑤 ) ) -s ( 𝑣 ·s 𝑤 ) ) } ) )