1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
15 set "baseuri" "cic:/matita/integration_algebras/".
17 include "vector_spaces.ma".
18 include "lattices.ma".
20 (**************** Riesz Spaces ********************)
22 record pre_riesz_space (K:ordered_field_ch0) : Type \def
23 { rs_vector_space:> vector_space K;
25 rs_with: os_carrier rs_lattice_ = rs_vector_space
28 lemma rs_lattice: ∀K:ordered_field_ch0.pre_riesz_space K → lattice.
32 | apply (eq_rect ? ? (λC:Type.C→C→C) ? ? (rs_with ? V));
34 | apply (eq_rect ? ? (λC:Type.C→C→C) ? ? (rs_with ? V));
38 (λa:Type.λH:os_carrier (rs_lattice_ ? V)=a.
40 (eq_rect Type (rs_lattice_ K V) (λC:Type.C→C→C)
41 (l_join (rs_lattice_ K V)) a H)
42 (eq_rect Type (rs_lattice_ K V) (λC:Type.C→C→C)
43 (l_meet (rs_lattice_ K V)) a H))
46 apply l_lattice_properties
50 coercion cic:/matita/integration_algebras/rs_lattice.con.
52 record is_riesz_space (K:ordered_field_ch0) (V:pre_riesz_space K) : Prop ≝
53 { rs_compat_le_plus: ∀f,g,h:V. f≤g → f+h≤g+h;
54 rs_compat_le_times: ∀a:K.∀f:V. zero K≤a → zero V≤f → zero V≤a*f
57 record riesz_space (K:ordered_field_ch0) : Type \def
58 { rs_pre_riesz_space:> pre_riesz_space K;
59 rs_riesz_space_properties: is_riesz_space ? rs_pre_riesz_space
62 record is_positive_linear (K) (V:riesz_space K) (T:V→K) : Prop ≝
63 { positive: ∀u:V. os_le V 0 u → os_le K 0 (T u);
64 linear1: ∀u,v:V. T (u+v) = T u + T v;
65 linear2: ∀u:V.∀k:K. T (k*u) = k*(T u)
68 record sequentially_order_continuous (K) (V:riesz_space K) (T:V→K) : Prop ≝
70 ∀a:nat→V.∀l:V.is_increasing ? a → is_sup V a l →
71 is_increasing K (λn.T (a n)) ∧ tends_to ? (λn.T (a n)) (T l)
74 definition absolute_value \def λK.λS:riesz_space K.λf.l_join S f (-f).
76 (**************** Normed Riesz spaces ****************************)
78 definition is_riesz_norm ≝
79 λR:real.λV:riesz_space R.λnorm:norm R V.
80 ∀f,g:V. os_le V (absolute_value ? V f) (absolute_value ? V g) →
81 os_le R (n_function R V norm f) (n_function R V norm g).
83 record riesz_norm (R:real) (V:riesz_space R) : Type ≝
85 rn_riesz_norm_property: is_riesz_norm ? ? rn_norm
88 (*CSC: non fa la chiusura delle coercion verso funclass *)
89 definition rn_function ≝
90 λR:real.λV:riesz_space R.λnorm:riesz_norm ? V.
91 n_function R V (rn_norm ? ? norm).
93 coercion cic:/matita/integration_algebras/rn_function.con 1.
95 (************************** L-SPACES *************************************)
97 record is_l_space (R:real) (V:riesz_space R) (norm:riesz_norm ? V) : Prop ≝
98 { ls_banach: is_complete ? V (induced_distance ? ? norm);
99 ls_linear: ∀f,g:V. le ? V 0 f → le ? V 0 g → norm (f+g) = norm f + norm g
102 (******************** ARCHIMEDEAN RIESZ SPACES ***************************)
104 record is_archimedean_riesz_space (K) (S:riesz_space K) : Prop
106 { ars_archimedean: ∃u:S.∀n.∀a.∀p:n > O.
108 (absolute_value ? S a)
109 ((inv K (sum_field K n) (not_eq_sum_field_zero K n p))* u) →
113 record archimedean_riesz_space (K:ordered_field_ch0) : Type \def
114 { ars_riesz_space:> riesz_space K;
115 ars_archimedean_property: is_archimedean_riesz_space ? ars_riesz_space
118 definition is_weak_unit ≝
119 (* This definition is by Spitters. He cites Fremlin 353P, but:
120 1. that theorem holds only in f-algebras (as in Spitters, but we are
121 defining it on Riesz spaces)
122 2. Fremlin proves |x|/\u=0 \to u=0. How do we remove the absolute value?
123 λR:real.λV:archimedean_riesz_space R.λunit: V.
124 ∀x:V. meet x unit = 0 → u = 0.
125 3. Fremlin proves u > 0 implies x /\ u > 0 > 0 for Archimedean spaces
126 only. We pick this definition for now.
127 *) λR:real.λV:archimedean_riesz_space R.λe:V.
128 ∀v:V. lt V 0 v → lt V 0 (l_meet V v e).
130 (* Here we are avoiding a construction (the quotient space to define
131 f=g iff I(|f-g|)=0 *)
132 record integration_riesz_space (R:real) : Type \def
133 { irs_archimedean_riesz_space:> archimedean_riesz_space R;
134 irs_unit: irs_archimedean_riesz_space;
135 irs_weak_unit: is_weak_unit ? ? irs_unit;
136 integral: irs_archimedean_riesz_space → R;
137 irs_positive_linear: is_positive_linear ? ? integral;
139 ∀f:irs_archimedean_riesz_space.
141 (λn.integral (l_meet irs_archimedean_riesz_space f
142 ((sum_field R n)*irs_unit)))
145 ∀f:irs_archimedean_riesz_space.
148 integral (l_meet irs_archimedean_riesz_space f
149 ((inv ? (sum_field R (S n))
150 (not_eq_sum_field_zero R (S n) (le_S_S O n (le_O_n n)))
153 ∀f,g:irs_archimedean_riesz_space.
154 integral (absolute_value ? irs_archimedean_riesz_space (f - g)) = 0 → f=g
157 definition induced_norm_fun ≝
158 λR:real.λV:integration_riesz_space R.λf:V.
159 integral ? V (absolute_value ? ? f).
161 lemma induced_norm_is_norm:
162 ∀R:real.∀V:integration_riesz_space R.is_norm R V (induced_norm_fun ? V).
166 [ apply mk_is_semi_norm;
167 [ unfold induced_norm_fun;
170 [ apply (irs_positive_linear ? V)
175 unfold induced_norm_fun;
179 unfold induced_norm_fun;
184 unfold induced_norm_fun in H;
185 apply irs_quotient_space1;
188 rewrite < eq_zero_opp_zero;
189 rewrite > zero_neutral;
194 definition induced_norm ≝
195 λR:real.λV:integration_riesz_space R.
196 mk_norm ? ? (induced_norm_fun ? V) (induced_norm_is_norm ? V).
198 lemma is_riesz_norm_induced_norm:
199 ∀R:real.∀V:integration_riesz_space R.
200 is_riesz_norm ? ? (induced_norm ? V).
202 unfold is_riesz_norm;
206 unfold induced_norm_fun;
211 definition induced_riesz_norm ≝
212 λR:real.λV:integration_riesz_space R.
213 mk_riesz_norm ? ? (induced_norm ? V) (is_riesz_norm_induced_norm ? V).
215 definition distance_induced_by_integral ≝
216 λR:real.λV:integration_riesz_space R.
217 induced_distance ? ? (induced_norm R V).
219 definition is_complete_integration_riesz_space ≝
220 λR:real.λV:integration_riesz_space R.
221 is_complete ? ? (distance_induced_by_integral ? V).
223 record complete_integration_riesz_space (R:real) : Type ≝
224 { cirz_integration_riesz_space:> integration_riesz_space R;
225 cirz_complete_integration_riesz_space_property:
226 is_complete_integration_riesz_space ? cirz_integration_riesz_space
229 (* now we prove that any complete integration riesz space is an L-space *)
231 (*theorem is_l_space_l_space_induced_by_integral:
232 ∀R:real.∀V:complete_integration_riesz_space R.
233 is_l_space ? ? (induced_riesz_norm ? V).
236 [ apply cirz_complete_integration_riesz_space_property
238 unfold induced_riesz_norm;
242 unfold induced_norm_fun;
248 (**************************** f-ALGEBRAS ********************************)
250 record is_algebra (K: field) (V:vector_space K) (mult:V→V→V) (one:V) : Prop
252 { (* ring properties *)
253 a_ring: is_ring V mult one;
254 (* algebra properties *)
255 a_associative_left: ∀a,f,g. a * (mult f g) = mult (a * f) g;
256 a_associative_right: ∀a,f,g. a * (mult f g) = mult f (a * g)
259 record algebra (K: field) (V:vector_space K) (a_one:V) : Type \def
261 a_algebra_properties: is_algebra ? ? a_mult a_one
264 interpretation "Algebra product" 'times a b =
265 (cic:/matita/integration_algebras/a_mult.con _ _ _ a b).
267 definition ring_of_algebra ≝
268 λK.λV:vector_space K.λone:V.λA:algebra ? V one.
269 mk_ring V (a_mult ? ? ? A) one
270 (a_ring ? ? ? ? (a_algebra_properties ? ? ? A)).
272 coercion cic:/matita/integration_algebras/ring_of_algebra.con.
274 record is_f_algebra (K) (S:archimedean_riesz_space K) (one: S)
275 (A:algebra ? S one) : Prop
279 os_le S 0 f → os_le S 0 g → os_le S 0 (a_mult ? ? ? A f g);
282 l_meet S f g = 0 → l_meet S (a_mult ? ? ? A h f) g = 0
285 record f_algebra (K:ordered_field_ch0) (R:archimedean_riesz_space K) (one:R) :
287 { fa_algebra:> algebra ? R one;
288 fa_f_algebra_properties: is_f_algebra ? ? ? fa_algebra
291 (* to be proved; see footnote 2 in the paper by Spitters *)
292 axiom symmetric_a_mult:
293 ∀K,R,one.∀A:f_algebra K R one. symmetric ? (a_mult ? ? ? A).
295 record integration_f_algebra (R:real) : Type \def
296 { ifa_integration_riesz_space:> integration_riesz_space R;
298 f_algebra ? ifa_integration_riesz_space
299 (irs_unit ? ifa_integration_riesz_space)