Metamath Proof Explorer


Theorem decsmflem

Description: A nonincreasing function is Borel measurable. Proposition 121D (c) of Fremlin1 p. 36 . (Contributed by Glauco Siliprandi, 26-Jun-2021)

Ref Expression
Hypotheses decsmflem.x
|- F/ x ph
decsmflem.y
|- F/ y ph
decsmflem.a
|- ( ph -> A C_ RR )
decsmflem.f
|- ( ph -> F : A --> RR* )
decsmflem.i
|- ( ph -> A. x e. A A. y e. A ( x <_ y -> ( F ` y ) <_ ( F ` x ) ) )
decsmflem.j
|- J = ( topGen ` ran (,) )
decsmflem.b
|- B = ( SalGen ` J )
decsmflem.r
|- ( ph -> R e. RR* )
decsmflem.l
|- Y = { x e. A | R < ( F ` x ) }
decsmflem.c
|- C = sup ( Y , RR* , < )
decsmflem.d
|- D = ( -oo (,) C )
decsmflem.e
|- E = ( -oo (,] C )
Assertion decsmflem
|- ( ph -> E. b e. B Y = ( b i^i A ) )

Proof

Step Hyp Ref Expression
1 decsmflem.x
 |-  F/ x ph
2 decsmflem.y
 |-  F/ y ph
3 decsmflem.a
 |-  ( ph -> A C_ RR )
4 decsmflem.f
 |-  ( ph -> F : A --> RR* )
5 decsmflem.i
 |-  ( ph -> A. x e. A A. y e. A ( x <_ y -> ( F ` y ) <_ ( F ` x ) ) )
6 decsmflem.j
 |-  J = ( topGen ` ran (,) )
7 decsmflem.b
 |-  B = ( SalGen ` J )
8 decsmflem.r
 |-  ( ph -> R e. RR* )
9 decsmflem.l
 |-  Y = { x e. A | R < ( F ` x ) }
10 decsmflem.c
 |-  C = sup ( Y , RR* , < )
11 decsmflem.d
 |-  D = ( -oo (,) C )
12 decsmflem.e
 |-  E = ( -oo (,] C )
13 mnfxr
 |-  -oo e. RR*
14 13 a1i
 |-  ( ( ph /\ C e. Y ) -> -oo e. RR* )
15 ssrab2
 |-  { x e. A | R < ( F ` x ) } C_ A
16 9 15 eqsstri
 |-  Y C_ A
17 16 a1i
 |-  ( ph -> Y C_ A )
18 17 3 sstrd
 |-  ( ph -> Y C_ RR )
19 18 sselda
 |-  ( ( ph /\ C e. Y ) -> C e. RR )
20 14 19 6 7 iocborel
 |-  ( ( ph /\ C e. Y ) -> ( -oo (,] C ) e. B )
21 12 20 eqeltrid
 |-  ( ( ph /\ C e. Y ) -> E e. B )
22 nfrab1
 |-  F/_ x { x e. A | R < ( F ` x ) }
23 9 22 nfcxfr
 |-  F/_ x Y
24 nfcv
 |-  F/_ x RR*
25 nfcv
 |-  F/_ x <
26 23 24 25 nfsup
 |-  F/_ x sup ( Y , RR* , < )
27 10 26 nfcxfr
 |-  F/_ x C
28 27 23 nfel
 |-  F/ x C e. Y
29 1 28 nfan
 |-  F/ x ( ph /\ C e. Y )
30 3 adantr
 |-  ( ( ph /\ C e. Y ) -> A C_ RR )
31 4 adantr
 |-  ( ( ph /\ C e. Y ) -> F : A --> RR* )
32 5 adantr
 |-  ( ( ph /\ C e. Y ) -> A. x e. A A. y e. A ( x <_ y -> ( F ` y ) <_ ( F ` x ) ) )
33 8 adantr
 |-  ( ( ph /\ C e. Y ) -> R e. RR* )
34 simpr
 |-  ( ( ph /\ C e. Y ) -> C e. Y )
35 29 30 31 32 33 9 10 34 12 pimdecfgtioc
 |-  ( ( ph /\ C e. Y ) -> Y = ( E i^i A ) )
36 ineq1
 |-  ( b = E -> ( b i^i A ) = ( E i^i A ) )
37 36 rspceeqv
 |-  ( ( E e. B /\ Y = ( E i^i A ) ) -> E. b e. B Y = ( b i^i A ) )
38 21 35 37 syl2anc
 |-  ( ( ph /\ C e. Y ) -> E. b e. B Y = ( b i^i A ) )
39 6 7 iooborel
 |-  ( -oo (,) C ) e. B
40 11 39 eqeltri
 |-  D e. B
41 40 a1i
 |-  ( ph -> D e. B )
42 41 adantr
 |-  ( ( ph /\ -. C e. Y ) -> D e. B )
43 28 nfn
 |-  F/ x -. C e. Y
44 1 43 nfan
 |-  F/ x ( ph /\ -. C e. Y )
45 nfv
 |-  F/ y -. C e. Y
46 2 45 nfan
 |-  F/ y ( ph /\ -. C e. Y )
47 3 adantr
 |-  ( ( ph /\ -. C e. Y ) -> A C_ RR )
48 4 adantr
 |-  ( ( ph /\ -. C e. Y ) -> F : A --> RR* )
49 5 adantr
 |-  ( ( ph /\ -. C e. Y ) -> A. x e. A A. y e. A ( x <_ y -> ( F ` y ) <_ ( F ` x ) ) )
50 8 adantr
 |-  ( ( ph /\ -. C e. Y ) -> R e. RR* )
51 simpr
 |-  ( ( ph /\ -. C e. Y ) -> -. C e. Y )
52 44 46 47 48 49 50 9 10 51 11 pimdecfgtioo
 |-  ( ( ph /\ -. C e. Y ) -> Y = ( D i^i A ) )
53 ineq1
 |-  ( b = D -> ( b i^i A ) = ( D i^i A ) )
54 53 rspceeqv
 |-  ( ( D e. B /\ Y = ( D i^i A ) ) -> E. b e. B Y = ( b i^i A ) )
55 42 52 54 syl2anc
 |-  ( ( ph /\ -. C e. Y ) -> E. b e. B Y = ( b i^i A ) )
56 38 55 pm2.61dan
 |-  ( ph -> E. b e. B Y = ( b i^i A ) )