let M be non empty Reflexive symmetric triangle MetrStruct ; :: thesis: ( M is complete implies for a being Point of M st ex b being Point of M st dist a,b <> 0 holds
for X being infinite set holds
( WellSpace a,X is complete & ex S being non-empty bounded SetSequence of (WellSpace a,X) st
( S is closed & S is non-ascending & meet S is empty ) ) )
assume A1:
M is complete
; :: thesis: for a being Point of M st ex b being Point of M st dist a,b <> 0 holds
for X being infinite set holds
( WellSpace a,X is complete & ex S being non-empty bounded SetSequence of (WellSpace a,X) st
( S is closed & S is non-ascending & meet S is empty ) )
let a be Point of M; :: thesis: ( ex b being Point of M st dist a,b <> 0 implies for X being infinite set holds
( WellSpace a,X is complete & ex S being non-empty bounded SetSequence of (WellSpace a,X) st
( S is closed & S is non-ascending & meet S is empty ) ) )
assume A2:
ex b being Point of M st dist a,b <> 0
; :: thesis: for X being infinite set holds
( WellSpace a,X is complete & ex S being non-empty bounded SetSequence of (WellSpace a,X) st
( S is closed & S is non-ascending & meet S is empty ) )
consider b being Point of M such that
A3:
dist a,b <> 0
by A2;
A4:
b <> a
by A3, METRIC_1:1;
let X be infinite set ; :: thesis: ( WellSpace a,X is complete & ex S being non-empty bounded SetSequence of (WellSpace a,X) st
( S is closed & S is non-ascending & meet S is empty ) )
set W = WellSpace a,X;
thus
WellSpace a,X is complete
by A1, Th42; :: thesis: ex S being non-empty bounded SetSequence of (WellSpace a,X) st
( S is closed & S is non-ascending & meet S is empty )
set TW = TopSpaceMetr (WellSpace a,X);
consider f being Function of NAT ,X such that
A5:
f is one-to-one
by DICKSON:3;
defpred S1[ set , set ] means $2 = [(f . $1),b];
A6:
for x being set st x in NAT holds
ex y being set st
( y in the carrier of (TopSpaceMetr (WellSpace a,X)) & S1[x,y] )
proof
let x be
set ;
:: thesis: ( x in NAT implies ex y being set st
( y in the carrier of (TopSpaceMetr (WellSpace a,X)) & S1[x,y] ) )
assume A7:
x in NAT
;
:: thesis: ex y being set st
( y in the carrier of (TopSpaceMetr (WellSpace a,X)) & S1[x,y] )
take
[(f . x),b]
;
:: thesis: ( [(f . x),b] in the carrier of (TopSpaceMetr (WellSpace a,X)) & S1[x,[(f . x),b]] )
x in dom f
by A7, FUNCT_2:def 1;
then
f . x in rng f
by FUNCT_1:def 5;
hence
(
[(f . x),b] in the
carrier of
(TopSpaceMetr (WellSpace a,X)) &
S1[
x,
[(f . x),b]] )
by A4, Th38;
:: thesis: verum
end;
consider s being Function of NAT ,the carrier of (TopSpaceMetr (WellSpace a,X)) such that
A8:
for x being set st x in NAT holds
S1[x,s . x]
from FUNCT_2:sch 1(A6);
deffunc H1( set ) -> set = {(s . $1)};
A9:
for x being set st x in NAT holds
H1(x) in bool the carrier of (TopSpaceMetr (WellSpace a,X))
consider S being SetSequence of (TopSpaceMetr (WellSpace a,X)) such that
A11:
for x being set st x in NAT holds
S . x = H1(x)
from FUNCT_2:sch 2(A9);
then A13:
S is non-empty
by FUNCT_1:def 15;
reconsider rngs = rng s as Subset of (TopSpaceMetr (WellSpace a,X)) ;
set F = { {x} where x is Element of (TopSpaceMetr (WellSpace a,X)) : x in rngs } ;
reconsider F = { {x} where x is Element of (TopSpaceMetr (WellSpace a,X)) : x in rngs } as Subset-Family of (TopSpaceMetr (WellSpace a,X)) by RELSET_2:16;
rng S c= F
then consider R being non-empty closed SetSequence of (TopSpaceMetr (WellSpace a,X)) such that
A16:
R is non-ascending
and
A17:
( F is locally_finite & S is one-to-one implies meet R = {} )
and
A18:
for i being natural number ex Si being Subset-Family of (TopSpaceMetr (WellSpace a,X)) st
( R . i = Cl (union Si) & Si = { (S . j) where j is Element of NAT : j >= i } )
by A13, Th23;
reconsider R' = R as non-empty SetSequence of (WellSpace a,X) ;
dist a,b > 0
by A3, METRIC_1:5;
then A19:
2 * (dist a,b) > 0
by XREAL_1:131;
A20:
now let x,
y be
Point of
(WellSpace a,X);
:: thesis: ( x in rngs & y in rngs & x <> y implies dist x,y = 2 * (dist a,b) )assume A21:
(
x in rngs &
y in rngs &
x <> y )
;
:: thesis: dist x,y = 2 * (dist a,b)consider x1 being
set such that A22:
(
x1 in dom s &
s . x1 = x )
by A21, FUNCT_1:def 5;
consider y1 being
set such that A23:
(
y1 in dom s &
s . y1 = y )
by A21, FUNCT_1:def 5;
(
x = [(f . x1),b] &
y = [(f . y1),b] )
by A8, A22, A23;
then
(well_dist a,X) . x,
y = (dist b,a) + (dist a,b)
by A21, Def10;
hence
dist x,
y = 2
* (dist a,b)
;
:: thesis: verum end;
now let i be
natural number ;
:: thesis: R' . i is bounded consider Si being
Subset-Family of
(TopSpaceMetr (WellSpace a,X)) such that A24:
R . i = Cl (union Si)
and A25:
Si = { (S . j) where j is Element of NAT : j >= i }
by A18;
reconsider SI =
union Si as
Subset of
(WellSpace a,X) ;
now let x,
y be
Point of
(WellSpace a,X);
:: thesis: ( x in SI & y in SI implies dist x,y <= 2 * (dist a,b) )assume A26:
(
x in SI &
y in SI )
;
:: thesis: dist x,y <= 2 * (dist a,b)consider xS being
set such that A27:
(
x in xS &
xS in Si )
by A26, TARSKI:def 4;
consider yS being
set such that A28:
(
y in yS &
yS in Si )
by A26, TARSKI:def 4;
consider j1 being
Element of
NAT such that A29:
(
xS = S . j1 &
j1 >= i )
by A25, A27;
consider j2 being
Element of
NAT such that A30:
(
yS = S . j2 &
j2 >= i )
by A25, A28;
(
dom s = NAT &
dom S = NAT )
by FUNCT_2:def 1;
then
(
s . j1 in rngs &
S . j1 = {(s . j1)} &
s . j2 in rngs &
S . j2 = {(s . j2)} )
by A11, FUNCT_1:def 5;
then
(
x in rngs &
y in rngs & (
x = y or
x <> y ) )
by A27, A28, A29, A30, TARSKI:def 1;
hence
dist x,
y <= 2
* (dist a,b)
by A19, A20, METRIC_1:1;
:: thesis: verum end; then
SI is
bounded
by A19, TBSP_1:def 9;
hence
R' . i is
bounded
by A24, Th8;
:: thesis: verum end;
then reconsider R' = R' as non-empty bounded SetSequence of (WellSpace a,X) by Def1;
take
R'
; :: thesis: ( R' is closed & R' is non-ascending & meet R' is empty )
thus
( R' is closed & R' is non-ascending )
by A16, Th7; :: thesis: meet R' is empty
A31:
for x, y being Point of (WellSpace a,X) st x <> y & x in rngs & y in rngs holds
dist x,y >= 2 * (dist a,b)
by A20;
hence
meet R' is empty
by A17, A19, A31, Lm7, FUNCT_2:25; :: thesis: verum