set cB = system_right_uniformity TG;
now ( system_right_uniformity TG is quasi_basis & system_right_uniformity TG is axiom_UP1 & system_right_uniformity TG is axiom_UP2 & system_right_uniformity TG is axiom_UP3 )hence
system_right_uniformity TG is
quasi_basis
;
( system_right_uniformity TG is axiom_UP1 & system_right_uniformity TG is axiom_UP2 & system_right_uniformity TG is axiom_UP3 )hence
system_right_uniformity TG is
axiom_UP1
;
( system_right_uniformity TG is axiom_UP2 & system_right_uniformity TG is axiom_UP3 )hence
system_right_uniformity TG is
axiom_UP2
;
system_right_uniformity TG is axiom_UP3 now for B1 being Element of system_right_uniformity TG ex B2 being Element of system_right_uniformity TG st B2 * B2 c= B1let B1 be
Element of
system_right_uniformity TG;
ex B2 being Element of system_right_uniformity TG st B2 * B2 c= B1
B1 in system_right_uniformity TG
;
then consider U being
a_neighborhood of
0_ TG such that A17:
B1 = element_right_uniformity U
;
U is
a_neighborhood of
(0_ TG) + (0_ TG)
by GROUP_1A:def 3;
then consider A,
B being
open a_neighborhood of
0_ TG such that A17bis:
A + B c= U
by GROUP_1A:354;
reconsider AB =
A /\ B as
a_neighborhood of
0_ TG by CONNSP_2:2;
(
AB c= A &
AB c= B )
by XBOOLE_1:17;
then A18:
AB + AB c= A + B
by Th3;
set B2 =
element_right_uniformity AB;
element_right_uniformity AB in system_right_uniformity TG
;
then reconsider B2 =
element_right_uniformity AB as
Element of
system_right_uniformity TG ;
B2 * B2 c= B1
proof
let t be
object ;
TARSKI:def 3 ( not t in B2 * B2 or t in B1 )
assume A19:
t in B2 * B2
;
t in B1
consider R1,
R2 being
Relation of the
carrier of
TG such that A20:
R1 = B2
and
R2 = B2
and
B2 * B2 = R1 * R2
;
t in { [x,y] where x, y is Element of TG : ex z being Element of TG st
( [x,z] in R1 & [z,y] in R1 ) }
by A19, A20, UNIFORM2:3;
then consider x,
y being
Element of
TG such that A23:
t = [x,y]
and A24:
ex
z being
Element of
TG st
(
[x,z] in R1 &
[z,y] in R1 )
;
consider z being
Element of
TG such that A25:
[x,z] in R1
and A26:
[z,y] in R1
by A24;
consider a,
b being
Element of
TG such that A27:
[x,z] = [a,b]
and A28:
b + (- a) in AB
by A20, A25;
A29:
(
x = a &
z = b )
by A27, XTUPLE_0:1;
consider c,
d being
Element of
TG such that A30:
[z,y] = [c,d]
and A31:
d + (- c) in AB
by A26, A20;
A32:
(
z = c &
y = d )
by A30, XTUPLE_0:1;
A33:
(d + (- c)) + (b + (- a)) =
y + ((- z) + (z + (- x)))
by A29, A32, RLVECT_1:def 3
.=
y + (((- z) + z) + (- x))
by RLVECT_1:def 3
.=
y + ((0_ TG) + (- x))
by GROUP_1A:def 4
.=
y + (- x)
by GROUP_1A:def 3
;
(d + (- c)) + (b + (- a)) in AB + AB
by A28, A31;
then
y + (- x) in U
by A18, A33, A17bis;
hence
t in B1
by A17, A23;
verum
end; hence
ex
B2 being
Element of
system_right_uniformity TG st
B2 * B2 c= B1
;
verum end; hence
system_right_uniformity TG is
axiom_UP3
;
verum end;
then
ex US being strict UniformSpace st
( the carrier of US = the carrier of TG & the entourages of US = <.(system_right_uniformity TG).] )
by Th7;
hence
UniformSpaceStr(# the carrier of TG,<.(system_right_uniformity TG).] #) is non empty UniformSpace
; verum