let p be Real; :: thesis: ( 1 <= p implies for lp being RealNormSpace st lp = NORMSTR(# (the_set_of_RealSequences_l^ p),(Zero_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(Add_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(Mult_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(l_norm^ p) #) holds
for vseq being sequence of lp st vseq is CCauchy holds
vseq is convergent )
assume A1:
1 <= p
; :: thesis: for lp being RealNormSpace st lp = NORMSTR(# (the_set_of_RealSequences_l^ p),(Zero_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(Add_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(Mult_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(l_norm^ p) #) holds
for vseq being sequence of lp st vseq is CCauchy holds
vseq is convergent
A2:
1 / p > 0
by A1, XREAL_1:141;
A3: p * (1 / p) =
(p * 1) / p
by XCMPLX_1:75
.=
1
by A1, XCMPLX_1:60
;
let lp be RealNormSpace; :: thesis: ( lp = NORMSTR(# (the_set_of_RealSequences_l^ p),(Zero_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(Add_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(Mult_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(l_norm^ p) #) implies for vseq being sequence of lp st vseq is CCauchy holds
vseq is convergent )
assume A4:
lp = NORMSTR(# (the_set_of_RealSequences_l^ p),(Zero_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(Add_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(Mult_ (the_set_of_RealSequences_l^ p),Linear_Space_of_RealSequences ),(l_norm^ p) #)
; :: thesis: for vseq being sequence of lp st vseq is CCauchy holds
vseq is convergent
let vseq be sequence of lp; :: thesis: ( vseq is CCauchy implies vseq is convergent )
assume A5:
vseq is CCauchy
; :: thesis: vseq is convergent
defpred S1[ set , set ] means ex i being Element of NAT st
( $1 = i & ex rseqi being Real_Sequence st
( ( for n being Element of NAT holds rseqi . n = (seq_id (vseq . n)) . i ) & rseqi is convergent & $2 = lim rseqi ) );
A6:
for x being set st x in NAT holds
ex y being set st
( y in REAL & S1[x,y] )
proof
let x be
set ;
:: thesis: ( x in NAT implies ex y being set st
( y in REAL & S1[x,y] ) )
assume A7:
x in NAT
;
:: thesis: ex y being set st
( y in REAL & S1[x,y] )
reconsider i =
x as
Element of
NAT by A7;
deffunc H1(
Element of
NAT )
-> Element of
REAL =
(seq_id (vseq . $1)) . i;
consider rseqi being
Real_Sequence such that A8:
for
n being
Element of
NAT holds
rseqi . n = H1(
n)
from SEQ_1:sch 1();
A9:
rseqi is
convergent
proof
now let e1 be
real number ;
:: thesis: ( e1 > 0 implies ex k being Element of NAT st
for m being Element of NAT st k <= m holds
abs ((rseqi . m) - (rseqi . k)) < e1 )assume A10:
e1 > 0
;
:: thesis: ex k being Element of NAT st
for m being Element of NAT st k <= m holds
abs ((rseqi . m) - (rseqi . k)) < e1reconsider e =
e1 as
Real by XREAL_0:def 1;
thus
ex
k being
Element of
NAT st
for
m being
Element of
NAT st
k <= m holds
abs ((rseqi . m) - (rseqi . k)) < e1
:: thesis: verumproof
consider k being
Element of
NAT such that A11:
for
n,
m being
Element of
NAT st
n >= k &
m >= k holds
||.((vseq . n) - (vseq . m)).|| < e
by A5, A10, RSSPACE3:10;
for
m being
Element of
NAT st
k <= m holds
abs ((rseqi . m) - (rseqi . k)) < e
proof
let m be
Element of
NAT ;
:: thesis: ( k <= m implies abs ((rseqi . m) - (rseqi . k)) < e )
assume A12:
k <= m
;
:: thesis: abs ((rseqi . m) - (rseqi . k)) < e
A13:
||.((vseq . m) - (vseq . k)).|| =
the
norm of
lp . ((vseq . m) - (vseq . k))
by NORMSP_1:def 1
.=
(Sum ((seq_id ((vseq . m) - (vseq . k))) rto_power p)) to_power (1 / p)
by A4, Def3
;
then
(Sum ((seq_id ((vseq . m) - (vseq . k))) rto_power p)) to_power (1 / p) < e
by A11, A12;
then A14:
((Sum ((seq_id ((vseq . m) - (vseq . k))) rto_power p)) to_power (1 / p)) to_power p < e to_power p
by A1, A13, Th1, NORMSP_1:8;
A15:
(seq_id ((vseq . m) - (vseq . k))) rto_power p is
summable
by A1, A4, Th10;
then
0 <= Sum ((seq_id ((vseq . m) - (vseq . k))) rto_power p)
by A15, SERIES_1:21;
then A17:
((Sum ((seq_id ((vseq . m) - (vseq . k))) rto_power p)) to_power (1 / p)) to_power p =
(Sum ((seq_id ((vseq . m) - (vseq . k))) rto_power p)) to_power ((1 / p) * p)
by A1, A2, HOLDER_1:2
.=
Sum ((seq_id ((vseq . m) - (vseq . k))) rto_power p)
by A3, POWER:30
;
A18:
(e to_power p) to_power (1 / p) =
e to_power ((1 / p) * p)
by A10, POWER:38
.=
e to_power 1
by A1, XCMPLX_1:107
.=
e
by POWER:30
;
A19:
((seq_id ((vseq . m) - (vseq . k))) rto_power p) . i <= Sum ((seq_id ((vseq . m) - (vseq . k))) rto_power p)
by A15, A16, RSSPACE2:4;
A26:
for
a,
b,
c being
Real st
a >= 0 &
b > 0 &
c > 0 holds
(a to_power b) to_power c = a to_power (b * c)
((seq_id ((vseq . m) - (vseq . k))) rto_power p) . i = (abs ((seq_id ((vseq . m) - (vseq . k))) . i)) to_power p
by Def1;
then A28:
(((seq_id ((vseq . m) - (vseq . k))) rto_power p) . i) to_power (1 / p) =
(abs ((seq_id ((vseq . m) - (vseq . k))) . i)) to_power 1
by A1, A2, A3, A26, COMPLEX1:132
.=
abs ((seq_id ((vseq . m) - (vseq . k))) . i)
by POWER:30
;
A29:
((seq_id ((vseq . m) - (vseq . k))) rto_power p) . i < e to_power p
by A14, A17, A19, XXREAL_0:2;
A30:
(
rseqi . m = (seq_id (vseq . m)) . i &
rseqi . k = (seq_id (vseq . k)) . i )
by A8;
reconsider vsem =
vseq . m,
vsek =
vseq . k as
VECTOR of
lp ;
vsem - vsek = (seq_id vsem) - (seq_id vsek)
by A1, A4, Th10;
then abs ((seq_id ((vseq . m) - (vseq . k))) . i) =
abs (((seq_id (vseq . m)) + (- (seq_id (vseq . k)))) . i)
by RSSPACE:3
.=
abs (((seq_id (vseq . m)) . i) + ((- (seq_id (vseq . k))) . i))
by SEQ_1:11
.=
abs (((seq_id (vseq . m)) . i) + (- ((seq_id (vseq . k)) . i)))
by SEQ_1:14
.=
abs ((rseqi . m) - (rseqi . k))
by A30
;
hence
abs ((rseqi . m) - (rseqi . k)) < e
by A2, A16, A18, A28, A29, Th1;
:: thesis: verum
end;
hence
ex
k being
Element of
NAT st
for
m being
Element of
NAT st
k <= m holds
abs ((rseqi . m) - (rseqi . k)) < e1
;
:: thesis: verum
end; end;
hence
rseqi is
convergent
by SEQ_4:58;
:: thesis: verum
end;
take y =
lim rseqi;
:: thesis: ( y in REAL & S1[x,y] )
thus
(
y in REAL &
S1[
x,
y] )
by A8, A9;
:: thesis: verum
end;
consider f being Function of NAT ,REAL such that
A31:
for x being set st x in NAT holds
S1[x,f . x]
from FUNCT_2:sch 1(A6);
reconsider tseq = f as Real_Sequence ;
A33:
for e being Real st e > 0 holds
ex k being Element of NAT st
for n being Element of NAT st n >= k holds
( ((seq_id tseq) - (seq_id (vseq . n))) rto_power p is summable & Sum (((seq_id tseq) - (seq_id (vseq . n))) rto_power p) < e )
proof
let e2 be
Real;
:: thesis: ( e2 > 0 implies ex k being Element of NAT st
for n being Element of NAT st n >= k holds
( ((seq_id tseq) - (seq_id (vseq . n))) rto_power p is summable & Sum (((seq_id tseq) - (seq_id (vseq . n))) rto_power p) < e2 ) )
assume A34:
e2 > 0
;
:: thesis: ex k being Element of NAT st
for n being Element of NAT st n >= k holds
( ((seq_id tseq) - (seq_id (vseq . n))) rto_power p is summable & Sum (((seq_id tseq) - (seq_id (vseq . n))) rto_power p) < e2 )
set e =
e2 / 2;
A35:
e2 / 2
> 0
by A34, XREAL_1:217;
A36:
e2 > e2 / 2
by A34, XREAL_1:218;
set e1 =
(e2 / 2) to_power (1 / p);
(e2 / 2) to_power (1 / p) > 0
by A35, POWER:39;
then consider k being
Element of
NAT such that A37:
for
n,
m being
Element of
NAT st
n >= k &
m >= k holds
||.((vseq . n) - (vseq . m)).|| < (e2 / 2) to_power (1 / p)
by A5, RSSPACE3:10;
A38:
for
m,
n being
Element of
NAT st
n >= k &
m >= k holds
(
(seq_id ((vseq . m) - (vseq . n))) rto_power p is
summable &
Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p) < e2 / 2 & ( for
i being
Element of
NAT holds
0 <= ((seq_id ((vseq . m) - (vseq . n))) rto_power p) . i ) )
proof
let m,
n be
Element of
NAT ;
:: thesis: ( n >= k & m >= k implies ( (seq_id ((vseq . m) - (vseq . n))) rto_power p is summable & Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p) < e2 / 2 & ( for i being Element of NAT holds 0 <= ((seq_id ((vseq . m) - (vseq . n))) rto_power p) . i ) ) )
assume A39:
(
n >= k &
m >= k )
;
:: thesis: ( (seq_id ((vseq . m) - (vseq . n))) rto_power p is summable & Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p) < e2 / 2 & ( for i being Element of NAT holds 0 <= ((seq_id ((vseq . m) - (vseq . n))) rto_power p) . i ) )
A40:
for
i being
Element of
NAT holds
((seq_id ((vseq . m) - (vseq . n))) rto_power p) . i >= 0
||.((vseq . m) - (vseq . n)).|| < (e2 / 2) to_power (1 / p)
by A37, A39;
then
the
norm of
lp . ((vseq . m) - (vseq . n)) < (e2 / 2) to_power (1 / p)
by NORMSP_1:def 1;
then A41:
(Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p)) to_power (1 / p) < (e2 / 2) to_power (1 / p)
by A4, Def3;
(seq_id ((vseq . m) - (vseq . n))) rto_power p is
summable
by A1, A4, Th10;
then A42:
0 <= Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p)
by A40, SERIES_1:21;
then A43:
((Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p)) to_power (1 / p)) to_power p =
(Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p)) to_power ((1 / p) * p)
by A1, A2, HOLDER_1:2
.=
Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p)
by A3, POWER:30
;
A44:
((e2 / 2) to_power (1 / p)) to_power p =
(e2 / 2) to_power ((1 / p) * p)
by A35, POWER:38
.=
(e2 / 2) to_power 1
by A1, XCMPLX_1:107
.=
e2 / 2
by POWER:30
;
(Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p)) to_power (1 / p) >= 0
by A2, A42, Lm1;
hence
(
(seq_id ((vseq . m) - (vseq . n))) rto_power p is
summable &
Sum ((seq_id ((vseq . m) - (vseq . n))) rto_power p) < e2 / 2 & ( for
i being
Element of
NAT holds
0 <= ((seq_id ((vseq . m) - (vseq . n))) rto_power p) . i ) )
by A1, A4, A40, A41, A43, A44, Th1, Th10;
:: thesis: verum
end;
A45:
for
n,
i being
Element of
NAT for
rseq being
Real_Sequence st ( for
m being
Element of
NAT holds
rseq . m = (Partial_Sums ((seq_id ((vseq . m) - (vseq . n))) rto_power p)) . i ) holds
(
rseq is
convergent &
lim rseq = (Partial_Sums (((seq_id tseq) - (seq_id (vseq . n))) rto_power p)) . i )
for
n being
Element of
NAT st
n >= k holds
(
((seq_id tseq) - (seq_id (vseq . n))) rto_power p is
summable &
Sum (((seq_id tseq) - (seq_id (vseq . n))) rto_power p) < e2 )
hence
ex
k being
Element of
NAT st
for
n being
Element of
NAT st
n >= k holds
(
((seq_id tseq) - (seq_id (vseq . n))) rto_power p is
summable &
Sum (((seq_id tseq) - (seq_id (vseq . n))) rto_power p) < e2 )
;
:: thesis: verum
end;
(seq_id tseq) rto_power p is summable
then reconsider tv = tseq as Point of lp by A1, A4, Th10;
for e being Real st e > 0 holds
ex m being Element of NAT st
for n being Element of NAT st n >= m holds
||.((vseq . n) - tv).|| < e
proof
let e be
Real;
:: thesis: ( e > 0 implies ex m being Element of NAT st
for n being Element of NAT st n >= m holds
||.((vseq . n) - tv).|| < e )
assume A72:
e > 0
;
:: thesis: ex m being Element of NAT st
for n being Element of NAT st n >= m holds
||.((vseq . n) - tv).|| < e
set e1 =
e to_power p;
e to_power p > 0
by A72, POWER:39;
then consider m being
Element of
NAT such that A73:
for
n being
Element of
NAT st
n >= m holds
(
((seq_id tseq) - (seq_id (vseq . n))) rto_power p is
summable &
Sum (((seq_id tseq) - (seq_id (vseq . n))) rto_power p) < e to_power p )
by A33;
now let n be
Element of
NAT ;
:: thesis: ( n >= m implies ||.((vseq . n) - tv).|| < e )assume A74:
n >= m
;
:: thesis: ||.((vseq . n) - tv).|| < eA75:
for
i being
Element of
NAT holds
(((seq_id tseq) - (seq_id (vseq . n))) rto_power p) . i >= 0
((seq_id tseq) - (seq_id (vseq . n))) rto_power p is
summable
by A73, A74;
then A76:
Sum (((seq_id tseq) - (seq_id (vseq . n))) rto_power p) >= 0
by A75, SERIES_1:21;
A77:
Sum (((seq_id tseq) - (seq_id (vseq . n))) rto_power p) < e to_power p
by A73, A74;
A78:
(e to_power p) to_power (1 / p) =
e to_power (p * (1 / p))
by A72, POWER:38
.=
e to_power 1
by A1, XCMPLX_1:107
.=
e
by POWER:30
;
(Sum (((seq_id tv) - (seq_id (vseq . n))) rto_power p)) to_power (1 / p) =
(Sum ((seq_id ((seq_id tv) - (seq_id (vseq . n)))) rto_power p)) to_power (1 / p)
by RSSPACE:3
.=
(Sum ((seq_id (tv - (vseq . n))) rto_power p)) to_power (1 / p)
by A1, A4, Th10
.=
the
norm of
lp . (tv - (vseq . n))
by A4, Def3
.=
||.(tv + (- (vseq . n))).||
by NORMSP_1:def 1
.=
||.(- ((vseq . n) - tv)).||
by RLVECT_1:47
.=
||.((vseq . n) - tv).||
by NORMSP_1:6
;
hence
||.((vseq . n) - tv).|| < e
by A2, A76, A77, A78, Th1;
:: thesis: verum end;
hence
ex
m being
Element of
NAT st
for
n being
Element of
NAT st
n >= m holds
||.((vseq . n) - tv).|| < e
;
:: thesis: verum
end;
hence
vseq is convergent
by NORMSP_1:def 9; :: thesis: verum