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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 *)
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15 set "baseuri" "cic:/matita/integration_algebras/".
19 record is_vector_space (K: field) (G:abelian_group) (emult:K→G→G) : Prop
21 { vs_nilpotent: ∀v. emult 0 v = 0;
22 vs_neutral: ∀v. emult 1 v = v;
23 vs_distributive: ∀a,b,v. emult (a + b) v = (emult a v) + (emult b v);
24 vs_associative: ∀a,b,v. emult (a * b) v = emult a (emult b v)
27 record vector_space (K:field): Type \def
28 { vs_abelian_group :> abelian_group;
29 emult: K → vs_abelian_group → vs_abelian_group;
30 vs_vector_space_properties :> is_vector_space ? vs_abelian_group emult
33 interpretation "Vector space external product" 'times a b =
34 (cic:/matita/integration_algebras/emult.con _ _ a b).
36 record is_semi_norm (R:real) (V: vector_space R) (semi_norm:V→R) : Prop \def
37 { sn_positive: ∀x:V. 0 ≤ semi_norm x;
38 sn_omogeneous: ∀a:R.∀x:V. semi_norm (a*x) = (abs ? a) * semi_norm x;
39 sn_triangle_inequality: ∀x,y:V. semi_norm (x + y) ≤ semi_norm x + semi_norm y
42 theorem eq_semi_norm_zero_zero:
43 ∀R:real.∀V:vector_space R.∀semi_norm:V→R.
44 is_semi_norm ? ? semi_norm →
51 record is_norm (R:real) (V:vector_space R) (norm:V → R) : Prop \def
52 { n_semi_norm:> is_semi_norm ? ? norm;
53 n_properness: ∀x:V. norm x = 0 → x = 0
56 record is_semi_distance (R:real) (C:Type) (semi_d: C→C→R) : Prop \def
57 { sd_positive: ∀x,y:C. 0 ≤ semi_d x y;
58 sd_properness: \forall x:C. semi_d x x = 0;
59 sd_triangle_inequality: ∀x,y,z:C. semi_d x z ≤ semi_d x y + semi_d z y
62 record is_distance (R:real) (C:Type) (d:C→C→R) : Prop \def
63 { d_semi_distance:> is_semi_distance ? ? d;
64 d_properness: ∀x,y:C. d x y = 0 → x=y
67 definition induced_distance ≝
68 λR:real.λV:vector_space R.λnorm:V→R.
71 theorem induced_distance_is_distance:
72 ∀R:real.∀V:vector_space R.∀norm:V→R.
73 is_norm ? ? norm → is_distance ? ? (induced_distance ? ? norm).
76 [ apply mk_is_semi_distance;
77 [ unfold induced_distance;
82 | unfold induced_distance;
86 rewrite > opp_inverse;
87 apply eq_semi_norm_zero_zero;
90 | unfold induced_distance;
95 | unfold induced_distance;
97 generalize in match (n_properness ? ? ? H ? H1);
104 record is_lattice (C:Type) (join,meet:C→C→C) : Prop \def
105 { (* abelian semigroup properties *)
106 l_comm_j: symmetric ? join;
107 l_associative_j: associative ? join;
108 l_comm_m: symmetric ? meet;
109 l_associative_m: associative ? meet;
110 (* other properties *)
111 l_adsorb_j_m: ∀f,g. join f (meet f g) = f;
112 l_adsorb_m_j: ∀f,g. meet f (join f g) = f
115 record lattice (C:Type) : Type \def
118 l_lattice_properties: is_lattice ? join meet
121 definition le \def λC:Type.λL:lattice C.λf,g. meet ? L f g = f.
123 interpretation "Lattice le" 'leq a b =
124 (cic:/matita/integration_algebras/le.con _ _ a b).
126 definition lt \def λC:Type.λL:lattice C.λf,g. le ? L f g ∧ f ≠ g.
128 interpretation "Lattice lt" 'lt a b =
129 (cic:/matita/integration_algebras/lt.con _ _ a b).
131 definition carrier_of_lattice ≝
132 λC:Type.λL:lattice C.C.
134 record is_riesz_space (K:ordered_field_ch0) (V:vector_space K)
135 (L:lattice (Type_OF_vector_space ? V))
138 { rs_compat_le_plus: ∀f,g,h. le ? L f g → le ? L (f+h) (g+h);
139 rs_compat_le_times: ∀a:K.∀f. of_le ? 0 a → le ? L 0 f → le ? L 0 (a*f)
142 record riesz_space (K:ordered_field_ch0) : Type \def
143 { rs_vector_space:> vector_space K;
144 rs_lattice:> lattice rs_vector_space;
145 rs_riesz_space_properties: is_riesz_space ? rs_vector_space rs_lattice
148 definition absolute_value \def λK.λS:riesz_space K.λf.join ? S f (-f).
150 record is_archimedean_riesz_space (K) (S:riesz_space K) : Prop
152 { ars_archimedean: ∃u.∀n.∀a.∀p:n > O.
154 (absolute_value ? S a)
155 ((inv ? (sum_field K n) (not_eq_sum_field_zero ? n p))* u) →
159 record archimedean_riesz_space (K:ordered_field_ch0) : Type \def
160 { ars_riesz_space:> riesz_space K;
161 ars_archimedean_property: is_archimedean_riesz_space ? ars_riesz_space
164 record is_integral (K) (R:archimedean_riesz_space K) (I:R→K) : Prop
166 { i_positive: ∀f:R. le ? R 0 f → of_le K 0 (I f);
167 i_linear1: ∀f,g:R. I (f + g) = I f + I g;
168 i_linear2: ∀f:R.∀k:K. I (k*f) = k*(I f)
171 definition is_weak_unit ≝
172 (* This definition is by Spitters. He cites Fremlin 353P, but:
173 1. that theorem holds only in f-algebras (as in Spitters, but we are
174 defining it on Riesz spaces)
175 2. Fremlin proves |x|/\u=0 \to u=0. How do we remove the absolute value?
176 λR:real.λV:archimedean_riesz_space R.λunit: V.
177 ∀x:V. meet x unit = 0 → u = 0.
178 3. Fremlin proves u > 0 implies x /\ u > 0 > 0 for Archimedean spaces
179 only. We pick this definition for now.
180 *) λR:real.λV:archimedean_riesz_space R.λe:V.
181 ∀v:V. lt ? V 0 v → lt ? V 0 (meet ? V v e).
183 (* Here we are avoiding a construction (the quotient space to define
184 f=g iff I(|f-g|)=0 *)
185 record integration_riesz_space (R:real) : Type \def
186 { irs_archimedean_riesz_space:> archimedean_riesz_space R;
187 irs_unit: irs_archimedean_riesz_space;
188 irs_weak_unit: is_weak_unit ? ? irs_unit;
189 integral: irs_archimedean_riesz_space → R;
190 irs_integral_properties: is_integral ? ? integral;
192 ∀f:irs_archimedean_riesz_space.
194 (λn.integral (meet ? irs_archimedean_riesz_space f
195 ((sum_field R n)*irs_unit)))
198 ∀f:irs_archimedean_riesz_space.
201 integral (meet ? irs_archimedean_riesz_space f
202 ((inv ? (sum_field R (S n))
203 (not_eq_sum_field_zero R (S n) (le_S_S O n (le_O_n n)))
206 ∀f,g:irs_archimedean_riesz_space.
207 integral (absolute_value ? irs_archimedean_riesz_space (f - g)) = 0 → f=g
210 definition induced_norm ≝
211 λR:real.λV:integration_riesz_space R.λf:V.
212 integral ? ? (absolute_value ? ? f).
214 lemma induced_norm_is_norm:
215 ∀R:real.∀V:integration_riesz_space R.is_norm ? V (induced_norm ? V).
218 [ apply mk_is_semi_norm;
219 [ unfold induced_norm;
222 [ apply (irs_integral_properties ? V)
236 unfold induced_norm in H;
237 apply irs_quotient_space1;
240 rewrite < eq_zero_opp_zero;
241 rewrite > zero_neutral;
246 definition distance_induced_by_integral ≝
247 λR:real.λV:integration_riesz_space R.
248 induced_distance ? ? (induced_norm R V).
250 theorem distance_induced_by_integral_is_distance:
251 ∀R:real.∀V:integration_riesz_space R.
252 is_distance ? ? (distance_induced_by_integral ? V).
254 unfold distance_induced_by_integral;
255 apply induced_distance_is_distance;
256 apply induced_norm_is_norm.
259 record is_algebra (K: field) (V:vector_space K) (mult:V→V→V) (one:V) : Prop
261 { (* ring properties *)
262 a_ring: is_ring V mult one;
263 (* algebra properties *)
264 a_associative_left: ∀a,f,g. a * (mult f g) = mult (a * f) g;
265 a_associative_right: ∀a,f,g. a * (mult f g) = mult f (a * g)
268 record algebra (K: field) (V:vector_space K) (a_one:V) : Type \def
270 a_algebra_properties: is_algebra ? ? a_mult a_one
273 interpretation "Algebra product" 'times a b =
274 (cic:/matita/integration_algebras/a_mult.con _ _ _ a b).
276 definition ring_of_algebra ≝
277 λK.λV:vector_space K.λone:V.λA:algebra ? V one.
278 mk_ring V (a_mult ? ? ? A) one
279 (a_ring ? ? ? ? (a_algebra_properties ? ? ? A)).
281 coercion cic:/matita/integration_algebras/ring_of_algebra.con.
283 record is_f_algebra (K) (S:archimedean_riesz_space K) (one: S)
284 (A:algebra ? S one) : Prop
288 le ? S 0 f → le ? S 0 g → le ? S 0 (a_mult ? ? ? A f g);
291 meet ? S f g = 0 → meet ? S (a_mult ? ? ? A h f) g = 0
294 record f_algebra (K:ordered_field_ch0) (R:archimedean_riesz_space K) (one:R) :
296 { fa_algebra:> algebra ? R one;
297 fa_f_algebra_properties: is_f_algebra ? ? ? fa_algebra
300 (* to be proved; see footnote 2 in the paper by Spitters *)
301 axiom symmetric_a_mult:
302 ∀K,R,one.∀A:f_algebra K R one. symmetric ? (a_mult ? ? ? A).
304 record integration_f_algebra (R:real) : Type \def
305 { ifa_integration_riesz_space:> integration_riesz_space R;
307 f_algebra ? ifa_integration_riesz_space
308 (irs_unit ? ifa_integration_riesz_space)