let A be uncountable set ; ex F being Subset-Family of (1TopSp [:A,A:]) st
( F is locally_finite & not F is sigma_discrete )
set TS = 1TopSp [:A,A:];
set F = { ([:{a},A:] \/ [:A,{a}:]) where a is Element of A : a in A } ;
{ ([:{a},A:] \/ [:A,{a}:]) where a is Element of A : a in A } c= bool [:A,A:]
proof
let f be
object ;
TARSKI:def 3 ( not f in { ([:{a},A:] \/ [:A,{a}:]) where a is Element of A : a in A } or f in bool [:A,A:] )
assume
f in { ([:{a},A:] \/ [:A,{a}:]) where a is Element of A : a in A }
;
f in bool [:A,A:]
then consider a being
Element of
A such that A1:
f = [:{a},A:] \/ [:A,{a}:]
and
a in A
;
(
[:{a},A:] c= [:A,A:] &
[:A,{a}:] c= [:A,A:] )
by ZFMISC_1:96;
then
[:{a},A:] \/ [:A,{a}:] c= [:A,A:]
by XBOOLE_1:8;
hence
f in bool [:A,A:]
by A1;
verum
end;
then reconsider F = { ([:{a},A:] \/ [:A,{a}:]) where a is Element of A : a in A } as Subset-Family of (1TopSp [:A,A:]) ;
take
F
; ( F is locally_finite & not F is sigma_discrete )
for z being Point of (1TopSp [:A,A:]) ex Z being Subset of (1TopSp [:A,A:]) st
( z in Z & Z is open & { O where O is Subset of (1TopSp [:A,A:]) : ( O in F & O meets Z ) } is finite )
proof
let z be
Point of
(1TopSp [:A,A:]);
ex Z being Subset of (1TopSp [:A,A:]) st
( z in Z & Z is open & { O where O is Subset of (1TopSp [:A,A:]) : ( O in F & O meets Z ) } is finite )
set Z =
{z};
reconsider Z =
{z} as
Subset of
(1TopSp [:A,A:]) ;
consider x,
y being
object such that
x in A
and
y in A
and A2:
z = [x,y]
by ZFMISC_1:def 2;
set yAAy =
{([:{y},A:] \/ [:A,{y}:])};
set xAAx =
{([:{x},A:] \/ [:A,{x}:])};
set UZ =
{ O where O is Subset of (1TopSp [:A,A:]) : ( O in F & O meets Z ) } ;
A3:
{ O where O is Subset of (1TopSp [:A,A:]) : ( O in F & O meets Z ) } c= {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])}
proof
let U be
object ;
TARSKI:def 3 ( not U in { O where O is Subset of (1TopSp [:A,A:]) : ( O in F & O meets Z ) } or U in {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])} )
assume
U in { O where O is Subset of (1TopSp [:A,A:]) : ( O in F & O meets Z ) }
;
U in {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])}
then consider O being
Subset of
(1TopSp [:A,A:]) such that A4:
U = O
and A5:
O in F
and A6:
O meets Z
;
consider u being
object such that A7:
u in O
and A8:
u in Z
by A6, XBOOLE_0:3;
consider a being
Element of
A such that A9:
O = [:{a},A:] \/ [:A,{a}:]
and
a in A
by A5;
now O in {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])}per cases
( u in [:{a},A:] or u in [:A,{a}:] )
by A9, A7, XBOOLE_0:def 3;
suppose
u in [:{a},A:]
;
O in {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])}then
[x,y] in [:{a},A:]
by A2, A8, TARSKI:def 1;
then
x in {a}
by ZFMISC_1:87;
then
x = a
by TARSKI:def 1;
then
O in {([:{x},A:] \/ [:A,{x}:])}
by A9, TARSKI:def 1;
hence
O in {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])}
by XBOOLE_0:def 3;
verum end; suppose
u in [:A,{a}:]
;
O in {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])}then
[x,y] in [:A,{a}:]
by A2, A8, TARSKI:def 1;
then
y in {a}
by ZFMISC_1:87;
then
y = a
by TARSKI:def 1;
then
O in {([:{y},A:] \/ [:A,{y}:])}
by A9, TARSKI:def 1;
hence
O in {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])}
by XBOOLE_0:def 3;
verum end; end; end;
hence
U in {([:{x},A:] \/ [:A,{x}:])} \/ {([:{y},A:] \/ [:A,{y}:])}
by A4;
verum
end;
(
z in Z &
Z is
open )
by PRE_TOPC:def 2, ZFMISC_1:31;
hence
ex
Z being
Subset of
(1TopSp [:A,A:]) st
(
z in Z &
Z is
open &
{ O where O is Subset of (1TopSp [:A,A:]) : ( O in F & O meets Z ) } is
finite )
by A3;
verum
end;
hence
F is locally_finite
; not F is sigma_discrete
not F is sigma_discrete
proof
consider a being
object such that A10:
a in A
by XBOOLE_0:def 1;
reconsider a =
a as
Element of
A by A10;
set aAAa =
[:{a},A:] \/ [:A,{a}:];
A11:
card A c= card F
proof
deffunc H1(
object )
-> set =
[:{$1},A:] \/ [:A,{$1}:];
consider d being
Function such that A12:
(
dom d = A & ( for
x being
object st
x in A holds
d . x = H1(
x) ) )
from FUNCT_1:sch 3();
for
a1,
a2 being
object st
a1 in dom d &
a2 in dom d &
d . a1 = d . a2 holds
a1 = a2
proof
let a1,
a2 be
object ;
( a1 in dom d & a2 in dom d & d . a1 = d . a2 implies a1 = a2 )
assume that A13:
a1 in dom d
and A14:
a2 in dom d
and A15:
d . a1 = d . a2
;
a1 = a2
a1 in {a1}
by ZFMISC_1:31;
then A16:
[a1,a1] in [:{a1},A:]
by A12, A13, ZFMISC_1:87;
(
H1(
a1)
= d . a1 &
H1(
a2)
= d . a2 )
by A12, A13, A14;
then
[a1,a1] in [:{a2},A:] \/ [:A,{a2}:]
by A15, A16, XBOOLE_0:def 3;
then
(
[a1,a1] in [:{a2},A:] or
[a1,a1] in [:A,{a2}:] )
by XBOOLE_0:def 3;
then A17:
a1 in {a2}
by ZFMISC_1:87;
assume
a1 <> a2
;
contradiction
hence
contradiction
by A17, TARSKI:def 1;
verum
end;
then A18:
d is
one-to-one
by FUNCT_1:def 4;
rng d c= F
hence
card A c= card F
by A12, A18, CARD_1:10;
verum
end;
assume
F is
sigma_discrete
;
contradiction
then consider f being
sigma_discrete FamilySequence of
(1TopSp [:A,A:]) such that A21:
F = Union f
;
defpred S1[
object ,
object ]
means ( ( $2
in f . $1 & not
f . $1 is
empty ) or ( $2
= [:{a},A:] \/ [:A,{a}:] &
f . $1 is
empty ) );
A22:
for
k being
object st
k in NAT holds
ex
f being
object st
(
f in F &
S1[
k,
f] )
consider Df being
sequence of
F such that A25:
for
k being
object st
k in NAT holds
S1[
k,
Df . k]
from FUNCT_2:sch 1(A22);
A26:
for
n being
Element of
NAT for
AD,
BD being
Element of
F st
S1[
n,
AD] &
S1[
n,
BD] holds
AD = BD
proof
let n be
Element of
NAT ;
for AD, BD being Element of F st S1[n,AD] & S1[n,BD] holds
AD = BDlet AD,
BD be
Element of
F;
( S1[n,AD] & S1[n,BD] implies AD = BD )
assume that A27:
S1[
n,
AD]
and A28:
S1[
n,
BD]
;
AD = BD
now AD = BDA29:
f . n is
discrete
by Def2;
BD in F
by A21, A28, PROB_1:12;
then consider b being
Element of
A such that A30:
BD = [:{b},A:] \/ [:A,{b}:]
and
b in A
;
AD in F
by A21, A27, PROB_1:12;
then consider a being
Element of
A such that A31:
AD = [:{a},A:] \/ [:A,{a}:]
and
a in A
;
b in {b}
by TARSKI:def 1;
then
[a,b] in [:A,{b}:]
by ZFMISC_1:87;
then A32:
[a,b] in BD
by A30, XBOOLE_0:def 3;
a in {a}
by TARSKI:def 1;
then
[a,b] in [:{a},A:]
by ZFMISC_1:87;
then
[a,b] in AD
by A31, XBOOLE_0:def 3;
then
AD meets BD
by A32, XBOOLE_0:3;
hence
AD = BD
by A27, A28, A29, Th6;
verum end;
hence
AD = BD
;
verum
end;
A33:
F c= Df .: NAT
A38:
not
card A c= omega
by CARD_3:def 14;
then
card NAT in card A
by CARD_1:4, CARD_1:47;
then
card NAT c= card F
by A11, CARD_1:3;
then
card NAT c< card F
by A11, A38, CARD_1:47, XBOOLE_0:def 8;
then A39:
card (Df .: NAT) c< card F
by CARD_1:67, XBOOLE_1:59;
then
card (Df .: NAT) c= card F
by XBOOLE_0:def 8;
then
card (Df .: NAT) in card F
by A39, CARD_1:3;
then
F \ (Df .: NAT) <> {}
by CARD_1:68;
hence
contradiction
by A33, XBOOLE_1:37;
verum
end;
hence
not F is sigma_discrete
; verum