let L be Lattice; ( L is lower-bounded implies for F being Filter of L st F <> the carrier of L holds
ex H being Filter of L st
( F c= H & H is being_ultrafilter ) )
given r being Element of L such that A1:
for p being Element of L holds
( r "/\" p = r & p "/\" r = r )
; LATTICES:def 13 for F being Filter of L st F <> the carrier of L holds
ex H being Filter of L st
( F c= H & H is being_ultrafilter )
A2:
for H being Filter of L st r in H holds
H = the carrier of L
let F be Filter of L; ( F <> the carrier of L implies ex H being Filter of L st
( F c= H & H is being_ultrafilter ) )
assume A4:
F <> the carrier of L
; ex H being Filter of L st
( F c= H & H is being_ultrafilter )
set X = { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } ;
A5:
for x being set st x in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } holds
( x is Subset of L & x is Filter of L )
A6:
for X1 being set st X1 in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } holds
( F,X1 are_c=-comparable & X1 <> the carrier of L )
A7:
for Z being set st Z c= { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } & Z is c=-linear holds
ex Y being set st
( Y in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } & ( for X1 being set st X1 in Z holds
X1 c= Y ) )
proof
set x = the
Element of
F;
let Z be
set ;
( Z c= { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } & Z is c=-linear implies ex Y being set st
( Y in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } & ( for X1 being set st X1 in Z holds
X1 c= Y ) ) )
assume that A8:
Z c= { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) }
and A9:
Z is
c=-linear
;
ex Y being set st
( Y in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } & ( for X1 being set st X1 in Z holds
X1 c= Y ) )
take Y =
union (Z \/ {F});
( Y in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } & ( for X1 being set st X1 in Z holds
X1 c= Y ) )
F in {F}
by TARSKI:def 1;
then A10:
F in Z \/ {F}
by XBOOLE_0:def 3;
the
Element of
F in F
;
then reconsider V =
Y as non
empty set by A10, TARSKI:def 4;
V c= the
carrier of
L
then reconsider V =
V as non
empty Subset of
L ;
now for p, q being Element of L holds
( ( p in V & q in V implies p "/\" q in V ) & ( p "/\" q in V implies ( p in V & q in V ) ) )let p,
q be
Element of
L;
( ( p in V & q in V implies p "/\" q in V ) & ( p "/\" q in V implies ( p in V & q in V ) ) )thus
(
p in V &
q in V implies
p "/\" q in V )
( p "/\" q in V implies ( p in V & q in V ) )proof
assume
p in V
;
( not q in V or p "/\" q in V )
then consider X1 being
set such that A13:
p in X1
and A14:
X1 in Z \/ {F}
by TARSKI:def 4;
A15:
(
X1 in Z or
X1 in {F} )
by A14, XBOOLE_0:def 3;
then A16:
( (
X1 in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } &
X1 in Z ) or
X1 = F )
by A8, TARSKI:def 1;
assume
q in V
;
p "/\" q in V
then consider X2 being
set such that A17:
q in X2
and A18:
X2 in Z \/ {F}
by TARSKI:def 4;
A19:
(
X2 in Z or
X2 in {F} )
by A18, XBOOLE_0:def 3;
then
( (
X2 in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } &
X2 in Z ) or
X2 = F )
by A8, TARSKI:def 1;
then
X1,
X2 are_c=-comparable
by A6, A9, A16, ORDINAL1:def 8;
then A20:
(
X1 c= X2 or
X2 c= X1 )
;
A21:
X1 is
Filter of
L
by A5, A8, A15, TARSKI:def 1;
X2 is
Filter of
L
by A5, A8, A19, TARSKI:def 1;
then
(
p "/\" q in X1 or
p "/\" q in X2 )
by A13, A17, A20, A21, Th9;
hence
p "/\" q in V
by A14, A18, TARSKI:def 4;
verum
end; assume
p "/\" q in V
;
( p in V & q in V )then consider X1 being
set such that A22:
p "/\" q in X1
and A23:
X1 in Z \/ {F}
by TARSKI:def 4;
(
X1 in Z or
X1 in {F} )
by A23, XBOOLE_0:def 3;
then
X1 is
Filter of
L
by A5, A8, TARSKI:def 1;
then
(
p in X1 &
q in X1 )
by A22, Th8;
hence
(
p in V &
q in V )
by A23, TARSKI:def 4;
verum end;
then reconsider V =
V as
Filter of
L by Th8;
then A26:
V <> the
carrier of
L
;
F c= V
by A10, TARSKI:def 4;
hence
Y in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) }
by A26;
for X1 being set st X1 in Z holds
X1 c= Y
let X1 be
set ;
( X1 in Z implies X1 c= Y )
assume
X1 in Z
;
X1 c= Y
then
X1 in Z \/ {F}
by XBOOLE_0:def 3;
hence
X1 c= Y
by ZFMISC_1:74;
verum
end;
F in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) }
by A4;
then consider Y being set such that
A27:
Y in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) }
and
A28:
for Z being set st Z in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) } & Z <> Y holds
not Y c= Z
by A7, ORDERS_1:65;
consider H being Subset of L such that
A29:
Y = H
and
A30:
F c= H
and
A31:
H is Filter of L
and
A32:
H <> the carrier of L
by A27;
reconsider H = H as Filter of L by A31;
take
H
; ( F c= H & H is being_ultrafilter )
thus
( F c= H & H <> the carrier of L )
by A30, A32; FILTER_0:def 3 for H being Filter of L st H c= H & H <> the carrier of L holds
H = H
let G be Filter of L; ( H c= G & G <> the carrier of L implies H = G )
assume that
A33:
H c= G
and
A34:
G <> the carrier of L
; H = G
F c= G
by A30, A33;
then
G in { A where A is Subset of L : ( F c= A & A is Filter of L & A <> the carrier of L ) }
by A34;
hence
H = G
by A28, A29, A33; verum