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Infratopological bornologies and Mackey-convergence of series

Abstract

In this paper some aspects of ínfratopological bornologies are discussed. First, it is shown that bornologies with countable basis are infratopological. Second, it is shown that the convergence of series presents some pathologies beyond this class.

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Infratopological bornologies and Mackey-convergence of series

Author: Canela, Miguel A.; Serrahima, Mercè
Publisher: Dipòsit Digital de Documents de la UAB
Year: 1986
DOI: 10.5565/PUBLMAT_302386_07
Source: https://ddd.uab.cat/pub/pubsecmat/02102978v30n2-3/02102978v30n2-3p101.pdf
Pub
.
Ma
.
UAB
Vol
.
30
n2
2-3
Des
.
1986
INFRATOPOLOGICAL
BORNOLOGIES
AND
MACKEY-CONVERGENCE
OF
SERIES
MiguelA
.
Canela
and
Me cé
Se ahima
SYNOPSIS
:
In
his
pape
some
aspec s
o ín a opological
bo nologies
a e discussed
.
Fi s ,
i
is
shown
ha
bo nologies
wi h
coun able
basi's
a e
in a opological
.
Second,
i
is
shown
ha
he
con e gence
o se ies
p esen s
some
:
pa hologies
beyond
his
class
.
We
,
bllow
closely
he
,
e minology
o
[51
and [4]
,
whe e
he
main
opics
conce ning
bo nological
spaces
can
be
,
ound
.
Roughly
speaking
;,
a
bo nology
is
iü a opological
when
:can
be
de ined
om
a
opologyin
he
usual
way
:
he
bounded
se s
:
a e
hose
which
a e
abso bed
by ze o
neighbou hoods
.
Mo e
p ecisely

le
(E,
S
)
be a
linea
bo nological
space, and
TS
he
Mackey
;
closu e
opolo-
gy
associá ed
o
his
space
.
.
The Von
Neumann
bo nology
o
TS
,
de-
no ed
by
,
BIT
S
,
is
de ined
as
ollows
:
a
subse
B
C
E'
is
bounded
when
o
e e y
ze o
neighbou hood
V,
he e
is
some
A
>-0
such ha
B
C

X
V

(T
;
is
abso bed
by
V)'
.
The
bo nology
1 is
said
o
be
in-
a opolog'cal
when

0=
BT0,

_
A
mo e use ul
cha ac e iza ion,
whichdoessno
in ol e
any
opology
is
he
ollowing~
12-1
i
P oposi iom
1
.
.
A
linea
bo nological
space
(
E,
0

)

is
-
in a opo-
logical
i 'and
only i
e e y
subse
B
C
E,
which
is
abso bed
o
e e y
bo ni
.Vo ous
subse
o
&
.
is
bounded
in

(E,R)
(
a
subse
UC
E

is
bo ni o ous
when
U
abso bs e e y
bounded
se
o
(E,
S
))
.
The
boundedsubse s
o
an
o dina y
opological
ec o
space
( he
Von
Neumann
bo nology) o m an in a opological
bo nology
.
Ne e heless,bo nologies
which
a e
no
in a opological
can
appea
when we
deal
wi h
equicon inuous
se s
.
We
e e
o
(1
;
_
.
,
example
p
.
166,
o
an
equicon inuous
bo nology
no
Kolmogo o
and
consequen ly
no
in a opological
.
We
see
nex
ha
spaces
wi h
coun able
basis
a a
also
in a opo-
logical
.
P oposi ion
2
.
_Le _
(E,
S
)
be a
sepa a ed
con ex
bo nological
space
and
suppose
ha
S
admi s
a
coun able
basis

(Bn
)
n
>
1
.
Then
Bis
in-
a opological
.
P oo
.
We
can
supposse
ha
he B
n
's
a e
absolu ely
con ex
and
ha
he
sequence
is
inc easing
.
Thus,
i
we deno e
by
~~
.
~~
n
he
gauge
o
B
n
,
we ob ainan inc easingsequenceo
no ms,
each
~~
.
lin
de ined
in
E
n =
Span
B
n
.To
make i
easie ,
we
de ine
llxli n
o
x
E
E
En
.
Le
A
be an
unbounded
subse
o
(E,
S
)
.
hen,
o
e e y
n,
we
can
ind
xn E A
wi h
llxn 11 n > n2
.
Fo
e e y
k,
we de ine
:
and
pu ing
:
ñk
=
1
min
(lixlll
k
',
. .
.,
llxkllk
'
l)
.
k
V
=
U

ñ
k
.
B
k
,
k
11
we
ob ain
a
bo ni o ous
subse o
E,
and
V
does
no abso b
A,
be-
cause, o
E> 0
a bi a y,i
n
>
E
:-l,
xn
does
no
belong
o
any
AkBk
:
a)

i
k
2
n,
we ha e

11
E
xnllk
1
Ek
ñ
k
a E
n
A
k > Xk
b)

i

1

_ k

<

n,

we

ha e

11

Ex
n1 ik
?

11

Ex
n
l I
n
>
en
2

>

n
>X
k*
ApplyingP oposi ion
1,
we
conclude
ha
(E,
S
)
is
in a opo-
logical
.
People
which
is
used
o
linea
bo nological
spaces
knows
ha
such
a
space
can
ail
o
ha e
he
p ope ies
ha
one
hopes
o
ind
in
Func ional
Analysis,
unless
some
ex a
assump ions
a é
aken
.
Res ic ion
o
in a opological
spaces
is en
example
o
ex a
assump-
ion
unde which
some
pa ologies
do
no appea
.
We will
see
he e
ha
he
con e gence
o se ies
does
no
wo k in
he
usual
way
when
we
pla-
ce
ou sel es
ou side
he
class
o
in a opological
bo nologies
.
A
se ies

2
:

x
nis
said
o be
Mackey-con e gen
in
a
linea
n
>
1
bo nological
space
when
he
sequence
,
(
Y-

x
k)
n>
1
o
pa ial
k=1
sums
is
Mackey-con e gen
."The
ollowing
esul s
a e
well-known
o
he
opological
con e gence
in
a
opological
ec o
space
.
Ou
con-
e gence
has
been
conside ed
in
[6]
.
P oposi ion
3
.
(
i
)
Le
(E,
S
)
be
a
Mackey-comple e
con exbo -
nological
space,
(xn
)
n Z 1 a
bounded
sequence
in
(E
B
),
and
(an
)
n

>
1

a
sequence
o eal
numbe s
such
ha

lan
1

is
i-
n
>_
1
ni e
.
Then,

2
:
an
xn is
Mackey-con e gen
.
n
i
1
(ii)
Le
(E,
S
)
be an
in a opological
con ex
-
bo nological
space,
and
(xn
)
n
>
1
'
a
sequencesuch
ha ,
o
e e y
sequence
o
eal
numbe s
(a
n
)
n
>

1
wi h

la
n
1

ini e,

he
se ies

,~

a
n

.

x
n

is
Mac-
n >
1

-
n
> 1
key-con e gen
.
Then
(xn)n
>
1is
bounded
.
P oo
.
(i)
.
Take
a
bounded
disk
B
con aining
(x
n
)
n
>
l,
and
deno e
is
a
Cauchy sequence
wi h
espec
o 11 . II
B
,
and,
(E,
S
)
being
Mackey-comple e,
i is
Mackey-con e gen
in
(E,
B
) .
(ü)
I
(x
n
)
n
>_
1

is
unbounded_ he e
is a
bo ni o ous
subse

V
which
does
no
abso b
his
sequence
.
Replacing
(xn
)
n

by a
sub-
á
1
sequencei
necessa y
n
i s
gauge
.
The
sequenceo
pa ial
sums

n a
k
x
k
)
,
'k-1

n
>
1
we
can
suppose
ha
x
11 EZ
n
2
V
o
e e y
n
.
Then
(n
~2
.
x
n
)

is
no
Mackey-con e gen
o
ze o
.
//
na
1
As we ha e
p e iously
announced,be will
show,
h ough
a
coun-
e example,
ha
he
assump ionon
(E,
S
)
in
pa
(ii)
o
he
p e-
ceding
P oposi ion
is
no
supe luous
.
Example
4
.
Le
E
be
he
space
o
measu ab'le
eal
unc ions
on
he
uni
in e al
I =
-
10,1
(wi h
he
s anda d
iden i ica ion),
p o ided
wi h
he
o de
bo nology
:
a
subse
A
C
E
is
bounded
i
he e
is
some
gE
:E,
wi h
g
a
0
and
I l
<
g
o
e e y
E
A
.
This
bo nology
is
con ex,
bu no
he
associa ed
in a opological
bo nology
.
So
E is
no
in a opological
.
De ail
:s
on
his
ac
can
be
' ound
in [3J
.

Mo eo e
he
Mackey-con e gence
ela i e
o
he
o de
bo nology
coincides
wi h
he
almos
e e ywhe e
con e gence
.
We
conside
he
sequence
(
n
)

de ined
as
ollows
:
(we
n
? 1
deno eby
X
T
he
cha ac e is ic
unc iono
a
subse
T o
I)
:
4
= 3
.
X

5
= 3
.
X

}

1

,
and
so on
.
10,1/41

'

(
4
.
z-
ho
Ob iously,
(
)
n

is
bouhded
in he
o de
bo nology
.
Ne e heless,
n ?
1
1

an
n
con e ges
almos e e ywhe ewhen

2
:

lan
1

con e ges
.
l
su ices o
conside
he
case
in
which
a
n
1
0
o all
n
.
Mo eo e ,
i
su ices,
in' his
case,
o
p o e
ha

a
n n
con e ges
in
n
'=
1
measu e,
because
o
an inc easing
sequence,
bo h
ypes
o
con e -
gence
a e
equi alen
.
Fo
each
n, we
deno e
:
Take
a
ixed
n
.
On each in e al
b
n
=

aj

gn =

aj j
2n-1
é
j
<2
n

2n-1
i
j<
2n
he
cons an alue
na
j
o
some
j,
2
n-1
5 j
<
2n
.
The e o e,
gn
exceeds
bn
on his
in e al
i
and
only i
a
j
>

n
1 b
n
.
Bu
his
happens
o
a
mos
n-1
o
hese
in e als
.
Thus
:
2
n-1
Take
now
an
a bi a y
E
>
0,
and
choose
N
such ha
:
b
n
<

n-1

<
E
.
2
n
2
N

n2N
k

k+11

he
unc ion
g
akes
2n
'
2n

n

Then
:
m(
{
x
:

1

9n
(X)
>
E })

<

m(
{

x
:g
n
(x)

>

b
n
})_`Z

n

<

E
.
n
Z
N

n > N

Zn-1
n
=N
This a gumen p o es ha

gn
con e ges
in
measu e,
and
so
n?
1
does

aj
j
.//
j
21
R
EFERENC
E
S
1
.
M
.
A
.
Canela
.
Bo nologí
a
equicon inua
en un
espacio
de
aplicaciones
lineales
con inuas
.
Re is a
de
la
Uni e sidad
de San ande ,
núm
.2,
pa e
1
.
(1979) (111-121)
.
2
.
M
.
A
.
Canela
.
Linea
bo nologies
and
associa ed
opologies
.
Collec
.
Ma h
.
32
(1981),
165-178
.
3
.
M
.
A
.
Canela
.
Som
e
classes
o linea
bo nologlcal
spaces
.
oc
.
Royal
Soc
.
Edinb
.
90
(1981),
155-161
.
4
.
í
.
Hogbe-Nlend
.
Théo ie
des
bo nologies
e
applica ions
.
Lec u e
No es
in
Ma hema ics
213
(Be lin
:
Sp inge ,
1971)
.
5
.
H
.
Hogbe-Nlend
.
Bo nology
and
unc ional
analysis
(Ams e dam
:
No h
Holland,
1978)
.
6
.
V
.
B
.
Mosca elli
.
Bases in
bo nologícal
spaces
.
S udiaMa h
.
50
(1974),
251-264
.
Rebu
el
día
27 de
.
juny
de 1986
Uni e si a
de
Ba celona
Dep
.
d
e
TeO ia
de
Funcions
Facul a de
Ma ema iques
G an
Via,
585
08007-BARCELONA
ESPANYA