fldextrspundgle - Mathbox for Thierry Arnoux

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Theorem fldextrspundgle 33713

Description: Inequality involving the degree of two different field extensions 𝐼 and 𝐽 of a same field 𝐹. Part of the proof of Proposition 5, Chapter 5, of [BourbakiAlg2] p. 116. (Contributed by Thierry Arnoux, 13-Oct-2025.)

**Hypotheses**
Ref	Expression
fldextrspunfld.k	⊢ 𝐾 = (𝐿 ↾_s 𝐹)
fldextrspunfld.i	⊢ 𝐼 = (𝐿 ↾_s 𝐺)
fldextrspunfld.j	⊢ 𝐽 = (𝐿 ↾_s 𝐻)
fldextrspunfld.2	⊢ (𝜑 → 𝐿 ∈ Field)
fldextrspunfld.3	⊢ (𝜑 → 𝐹 ∈ (SubDRing‘𝐼))
fldextrspunfld.4	⊢ (𝜑 → 𝐹 ∈ (SubDRing‘𝐽))
fldextrspunfld.5	⊢ (𝜑 → 𝐺 ∈ (SubDRing‘𝐿))
fldextrspunfld.6	⊢ (𝜑 → 𝐻 ∈ (SubDRing‘𝐿))
fldextrspunfld.7	⊢ (𝜑 → (𝐽[:]𝐾) ∈ ℕ₀)
fldextrspundgle.1	⊢ 𝐸 = (𝐿 ↾_s (𝐿 fldGen (𝐺 ∪ 𝐻)))

**Assertion**
Ref	Expression
fldextrspundgle	⊢ (𝜑 → (𝐸[:]𝐼) ≤ (𝐽[:]𝐾))

**Proof of Theorem fldextrspundgle**
Step	Hyp	Ref	Expression
1		eqid 2736	. . . 4 ⊢ (Base‘𝐿) = (Base‘𝐿)
2		fldextrspunfld.i	. . . 4 ⊢ 𝐼 = (𝐿 ↾_s 𝐺)
3		fldextrspundgle.1	. . . 4 ⊢ 𝐸 = (𝐿 ↾_s (𝐿 fldGen (𝐺 ∪ 𝐻)))
4		fldextrspunfld.2	. . . 4 ⊢ (𝜑 → 𝐿 ∈ Field)
5		fldextrspunfld.5	. . . 4 ⊢ (𝜑 → 𝐺 ∈ (SubDRing‘𝐿))
6		fldextrspunfld.6	. . . . 5 ⊢ (𝜑 → 𝐻 ∈ (SubDRing‘𝐿))
7	1	sdrgss 20786	. . . . 5 ⊢ (𝐻 ∈ (SubDRing‘𝐿) → 𝐻 ⊆ (Base‘𝐿))
8	6, 7	syl 17	. . . 4 ⊢ (𝜑 → 𝐻 ⊆ (Base‘𝐿))
9	1, 2, 3, 4, 5, 8	fldgenfldext 33703	. . 3 ⊢ (𝜑 → 𝐸/_FldExt𝐼)
10		extdgval 33692	. . 3 ⊢ (𝐸/_FldExt𝐼 → (𝐸[:]𝐼) = (dim‘((subringAlg ‘𝐸)‘(Base‘𝐼))))
11	9, 10	syl 17	. 2 ⊢ (𝜑 → (𝐸[:]𝐼) = (dim‘((subringAlg ‘𝐸)‘(Base‘𝐼))))
12		fldextrspunfld.k	. . . . . . . . 9 ⊢ 𝐾 = (𝐿 ↾_s 𝐹)
13		fldextrspunfld.j	. . . . . . . . 9 ⊢ 𝐽 = (𝐿 ↾_s 𝐻)
14		fldextrspunfld.3	. . . . . . . . 9 ⊢ (𝜑 → 𝐹 ∈ (SubDRing‘𝐼))
15		fldextrspunfld.4	. . . . . . . . 9 ⊢ (𝜑 → 𝐹 ∈ (SubDRing‘𝐽))
16		fldextrspunfld.7	. . . . . . . . 9 ⊢ (𝜑 → (𝐽[:]𝐾) ∈ ℕ₀)
17		eqid 2736	. . . . . . . . 9 ⊢ (RingSpan‘𝐿) = (RingSpan‘𝐿)
18		eqid 2736	. . . . . . . . 9 ⊢ ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻)) = ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻))
19		eqid 2736	. . . . . . . . 9 ⊢ (𝐿 ↾_s ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻))) = (𝐿 ↾_s ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻)))
20	12, 2, 13, 4, 14, 15, 5, 6, 16, 17, 18, 19	fldextrspunlem2 33712	. . . . . . . 8 ⊢ (𝜑 → ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻)) = (𝐿 fldGen (𝐺 ∪ 𝐻)))
21	20	oveq2d 7445	. . . . . . 7 ⊢ (𝜑 → (𝐿 ↾_s ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻))) = (𝐿 ↾_s (𝐿 fldGen (𝐺 ∪ 𝐻))))
22	21, 3	eqtr4di 2794	. . . . . 6 ⊢ (𝜑 → (𝐿 ↾_s ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻))) = 𝐸)
23	22	fveq2d 6908	. . . . 5 ⊢ (𝜑 → (subringAlg ‘(𝐿 ↾_s ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻)))) = (subringAlg ‘𝐸))
24	1	sdrgss 20786	. . . . . 6 ⊢ (𝐺 ∈ (SubDRing‘𝐿) → 𝐺 ⊆ (Base‘𝐿))
25	2, 1	ressbas2 17279	. . . . . 6 ⊢ (𝐺 ⊆ (Base‘𝐿) → 𝐺 = (Base‘𝐼))
26	5, 24, 25	3syl 18	. . . . 5 ⊢ (𝜑 → 𝐺 = (Base‘𝐼))
27	23, 26	fveq12d 6911	. . . 4 ⊢ (𝜑 → ((subringAlg ‘(𝐿 ↾_s ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻))))‘𝐺) = ((subringAlg ‘𝐸)‘(Base‘𝐼)))
28	27	fveq2d 6908	. . 3 ⊢ (𝜑 → (dim‘((subringAlg ‘(𝐿 ↾_s ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻))))‘𝐺)) = (dim‘((subringAlg ‘𝐸)‘(Base‘𝐼))))
29	12, 2, 13, 4, 14, 15, 5, 6, 16, 17, 18, 19	fldextrspunlem1 33710	. . 3 ⊢ (𝜑 → (dim‘((subringAlg ‘(𝐿 ↾_s ((RingSpan‘𝐿)‘(𝐺 ∪ 𝐻))))‘𝐺)) ≤ (𝐽[:]𝐾))
30	28, 29	eqbrtrrd 5165	. 2 ⊢ (𝜑 → (dim‘((subringAlg ‘𝐸)‘(Base‘𝐼))) ≤ (𝐽[:]𝐾))
31	11, 30	eqbrtrd 5163	1 ⊢ (𝜑 → (𝐸[:]𝐼) ≤ (𝐽[:]𝐾))

Colors of variables: wff setvar class

Syntax hints: → wi 4 = wceq 1540 ∈ wcel 2108 ∪ cun 3948 ⊆ wss 3950 class class class wbr 5141 ‘cfv 6559 (class class class)co 7429 ≤ cle 11292 ℕ₀cn0 12522 Basecbs 17243 ↾_s cress 17270 RingSpancrgspn 20602 Fieldcfield 20722 SubDRingcsdrg 20779 subringAlg csra 21162 fldGen cfldgen 33299 dimcldim 33636 /_FldExtcfldext 33676 [:]cextdg 33679

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1795 ax-4 1809 ax-5 1910 ax-6 1967 ax-7 2007 ax-8 2110 ax-9 2118 ax-10 2141 ax-11 2157 ax-12 2177 ax-ext 2707 ax-rep 5277 ax-sep 5294 ax-nul 5304 ax-pow 5363 ax-pr 5430 ax-un 7751 ax-reg 9628 ax-inf2 9677 ax-ac2 10499 ax-cnex 11207 ax-resscn 11208 ax-1cn 11209 ax-icn 11210 ax-addcl 11211 ax-addrcl 11212 ax-mulcl 11213 ax-mulrcl 11214 ax-mulcom 11215 ax-addass 11216 ax-mulass 11217 ax-distr 11218 ax-i2m1 11219 ax-1ne0 11220 ax-1rid 11221 ax-rnegex 11222 ax-rrecex 11223 ax-cnre 11224 ax-pre-lttri 11225 ax-pre-lttrn 11226 ax-pre-ltadd 11227 ax-pre-mulgt0 11228 ax-pre-sup 11229 ax-addf 11230

This theorem depends on definitions: df-bi 207 df-an 396 df-or 849 df-3or 1088 df-3an 1089 df-tru 1543 df-fal 1553 df-ex 1780 df-nf 1784 df-sb 2065 df-mo 2539 df-eu 2568 df-clab 2714 df-cleq 2728 df-clel 2815 df-nfc 2891 df-ne 2940 df-nel 3046 df-ral 3061 df-rex 3070 df-rmo 3379 df-reu 3380 df-rab 3436 df-v 3481 df-sbc 3788 df-csb 3899 df-dif 3953 df-un 3955 df-in 3957 df-ss 3967 df-pss 3970 df-nul 4333 df-if 4525 df-pw 4600 df-sn 4625 df-pr 4627 df-tp 4629 df-op 4631 df-uni 4906 df-int 4945 df-iun 4991 df-iin 4992 df-br 5142 df-opab 5204 df-mpt 5224 df-tr 5258 df-id 5576 df-eprel 5582 df-po 5590 df-so 5591 df-fr 5635 df-se 5636 df-we 5637 df-xp 5689 df-rel 5690 df-cnv 5691 df-co 5692 df-dm 5693 df-rn 5694 df-res 5695 df-ima 5696 df-pred 6319 df-ord 6385 df-on 6386 df-lim 6387 df-suc 6388 df-iota 6512 df-fun 6561 df-fn 6562 df-f 6563 df-f1 6564 df-fo 6565 df-f1o 6566 df-fv 6567 df-isom 6568 df-riota 7386 df-ov 7432 df-oprab 7433 df-mpo 7434 df-of 7694 df-rpss 7739 df-om 7884 df-1st 8010 df-2nd 8011 df-supp 8182 df-tpos 8247 df-frecs 8302 df-wrecs 8333 df-recs 8407 df-rdg 8446 df-1o 8502 df-2o 8503 df-oadd 8506 df-er 8741 df-map 8864 df-ixp 8934 df-en 8982 df-dom 8983 df-sdom 8984 df-fin 8985 df-fsupp 9398 df-sup 9478 df-inf 9479 df-oi 9546 df-r1 9800 df-rank 9801 df-dju 9937 df-card 9975 df-acn 9978 df-ac 10152 df-pnf 11293 df-mnf 11294 df-xr 11295 df-ltxr 11296 df-le 11297 df-sub 11490 df-neg 11491 df-div 11917 df-nn 12263 df-2 12325 df-3 12326 df-4 12327 df-5 12328 df-6 12329 df-7 12330 df-8 12331 df-9 12332 df-n0 12523 df-xnn0 12596 df-z 12610 df-dec 12730 df-uz 12875 df-rp 13031 df-xadd 13151 df-fz 13544 df-fzo 13691 df-seq 14039 df-exp 14099 df-hash 14366 df-word 14549 df-lsw 14597 df-concat 14605 df-s1 14630 df-substr 14675 df-pfx 14705 df-s2 14883 df-cj 15134 df-re 15135 df-im 15136 df-sqrt 15270 df-abs 15271 df-clim 15520 df-sum 15719 df-struct 17180 df-sets 17197 df-slot 17215 df-ndx 17227 df-base 17244 df-ress 17271 df-plusg 17306 df-mulr 17307 df-starv 17308 df-sca 17309 df-vsca 17310 df-ip 17311 df-tset 17312 df-ple 17313 df-ocomp 17314 df-ds 17315 df-unif 17316 df-hom 17317 df-cco 17318 df-0g 17482 df-gsum 17483 df-prds 17488 df-pws 17490 df-mre 17625 df-mrc 17626 df-mri 17627 df-acs 17628 df-proset 18336 df-drs 18337 df-poset 18355 df-ipo 18569 df-mgm 18649 df-sgrp 18728 df-mnd 18744 df-mhm 18792 df-submnd 18793 df-grp 18950 df-minusg 18951 df-sbg 18952 df-mulg 19082 df-subg 19137 df-ghm 19227 df-cntz 19331 df-cntr 19332 df-lsm 19650 df-cmn 19796 df-abl 19797 df-mgp 20134 df-rng 20146 df-ur 20175 df-ring 20228 df-cring 20229 df-oppr 20326 df-dvdsr 20349 df-unit 20350 df-invr 20380 df-dvr 20393 df-nzr 20505 df-subrng 20538 df-subrg 20562 df-rgspn 20603 df-rlreg 20686 df-domn 20687 df-idom 20688 df-drng 20723 df-field 20724 df-sdrg 20780 df-lmod 20852 df-lss 20922 df-lsp 20962 df-lmhm 21013 df-lmim 21014 df-lbs 21066 df-lvec 21094 df-sra 21164 df-rgmod 21165 df-cnfld 21357 df-zring 21450 df-dsmm 21744 df-frlm 21759 df-uvc 21795 df-lindf 21818 df-linds 21819 df-assa 21865 df-ind 32823 df-fldgen 33300 df-dim 33637 df-fldext 33680 df-extdg 33681

This theorem is referenced by: (None)

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