let p be Real; ( 1 <= p implies the_set_of_RealSequences_l^ p is linearly-closed )
assume A1:
p >= 1
; the_set_of_RealSequences_l^ p is linearly-closed
set W = the_set_of_RealSequences_l^ p;
A2:
for v, u being VECTOR of Linear_Space_of_RealSequences st v in the_set_of_RealSequences_l^ p & u in the_set_of_RealSequences_l^ p holds
v + u in the_set_of_RealSequences_l^ p
proof
let v,
u be
VECTOR of
Linear_Space_of_RealSequences;
( v in the_set_of_RealSequences_l^ p & u in the_set_of_RealSequences_l^ p implies v + u in the_set_of_RealSequences_l^ p )
assume that A3:
v in the_set_of_RealSequences_l^ p
and A4:
u in the_set_of_RealSequences_l^ p
;
v + u in the_set_of_RealSequences_l^ p
A5:
(seq_id (v + u)) rto_power p is
summable
proof
reconsider vq =
v as
Real_Sequence by FUNCT_2:66;
set up =
(seq_id u) rto_power p;
set vp =
(seq_id v) rto_power p;
set p1 = 1
/ p;
(seq_id v) rto_power p is
summable
by A1, A3, Def2;
then
Partial_Sums ((seq_id v) rto_power p) is
bounded_above
by A7, SERIES_1:17;
then consider r being
Real such that A10:
for
n being
object st
n in dom (Partial_Sums ((seq_id v) rto_power p)) holds
(Partial_Sums ((seq_id v) rto_power p)) . n < r
by SEQ_2:def 1;
A11:
1
/ p > 0
by A1, XREAL_1:139;
reconsider r =
r as
Real ;
A12:
Partial_Sums ((seq_id v) rto_power p) is
non-decreasing
by A7, SERIES_1:16;
then consider q being
Real such that A15:
for
n being
set st
n in dom (Partial_Sums ((seq_id v) rto_power p)) holds
((Partial_Sums ((seq_id v) rto_power p)) . n) to_power (1 / p) < q
;
reconsider uq =
u as
Real_Sequence by FUNCT_2:66;
A17:
(seq_id v) + (seq_id u) = seq_id (v + u)
by RSSPACE:2;
(seq_id u) rto_power p is
summable
by A1, A4, Def2;
then
Partial_Sums ((seq_id u) rto_power p) is
bounded_above
by A7, SERIES_1:17;
then consider r1 being
Real such that A18:
for
n being
object st
n in dom (Partial_Sums ((seq_id u) rto_power p)) holds
(Partial_Sums ((seq_id u) rto_power p)) . n < r1
by SEQ_2:def 1;
reconsider r1 =
r1 as
Real ;
A19:
Partial_Sums ((seq_id u) rto_power p) is
non-decreasing
by A7, SERIES_1:16;
then consider q1 being
Real such that A22:
for
n being
set st
n in dom (Partial_Sums ((seq_id u) rto_power p)) holds
((Partial_Sums ((seq_id u) rto_power p)) . n) to_power (1 / p) < q1
;
set g =
q + q1;
A24:
p * (1 / p) =
(p * 1) / p
by XCMPLX_1:74
.=
1
by A1, XCMPLX_1:60
;
now for n being Nat holds
( ( for n being Nat holds
( ( 0 < |.((vq + uq) . n).| or 0 = |.((vq + uq) . n).| ) & 0 <= ((vq + uq) rto_power p) . n ) ) & (Partial_Sums ((vq + uq) rto_power p)) . n < (q + q1) to_power p )let n be
Nat;
( ( for n being Nat holds
( ( 0 < |.((vq + uq) . n).| or 0 = |.((vq + uq) . n).| ) & 0 <= ((vq + uq) rto_power p) . n ) ) & (Partial_Sums ((vq + uq) rto_power p)) . n < (q + q1) to_power p )A25:
n in NAT
by ORDINAL1:def 12;
NAT = dom (Partial_Sums ((seq_id u) rto_power p))
by SEQ_1:2;
then A27:
((Partial_Sums ((seq_id u) rto_power p)) . n) to_power (1 / p) < q1
by A22, A25;
NAT = dom (Partial_Sums ((seq_id v) rto_power p))
by SEQ_1:2;
then A28:
(((Partial_Sums ((seq_id u) rto_power p)) . n) to_power (1 / p)) + (((Partial_Sums ((seq_id v) rto_power p)) . n) to_power (1 / p)) < q + q1
by A15, A27, XREAL_1:8, A25;
((Partial_Sums ((vq + uq) rto_power p)) . n) to_power (1 / p) <= (((Partial_Sums ((seq_id u) rto_power p)) . n) to_power (1 / p)) + (((Partial_Sums ((seq_id v) rto_power p)) . n) to_power (1 / p))
by A1, Th2;
then A29:
((Partial_Sums ((vq + uq) rto_power p)) . n) to_power (1 / p) < q + q1
by A28, XXREAL_0:2;
then A34:
0 <= ((vq + uq) rto_power p) . 0
;
A35:
(Partial_Sums ((vq + uq) rto_power p)) . 0 <= (Partial_Sums ((vq + uq) rto_power p)) . n
by A32, SEQM_3:11, SERIES_1:16;
then
0 <= (Partial_Sums ((vq + uq) rto_power p)) . n
by A34, SERIES_1:def 1;
then
((Partial_Sums ((vq + uq) rto_power p)) . n) to_power (1 / p) >= 0
by A11, Lm1;
hence
(Partial_Sums ((vq + uq) rto_power p)) . n < (q + q1) to_power p
by A1, A29, A26, A30, A35, A34, Th1, SERIES_1:def 1;
verum end;
then
for
n being
Nat holds
(
Partial_Sums ((vq + uq) rto_power p) is
bounded_above &
0 <= ((vq + uq) rto_power p) . n )
by SEQ_2:def 3;
hence
(seq_id (v + u)) rto_power p is
summable
by A17, SERIES_1:17;
verum
end;
thus
v + u in the_set_of_RealSequences_l^ p
by A1, A5, Def2;
verum
end;
for a being Real
for v being VECTOR of Linear_Space_of_RealSequences st v in the_set_of_RealSequences_l^ p holds
a * v in the_set_of_RealSequences_l^ p
hence
the_set_of_RealSequences_l^ p is linearly-closed
by A2, RLSUB_1:def 1; verum