author  hoelzl 
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parent 54259  71c701dc5bf9 
child 54263  c4159fe6fa46 
permissions  rwrr 
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(* title: HOL/Library/Topology_Euclidian_Space.thy 
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Author: Amine Chaieb, University of Cambridge 
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Author: Robert Himmelmann, TU Muenchen 

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Author: Brian Huffman, Portland State University 
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*) 
6 

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header {* Elementary topology in Euclidean space. *} 

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theory Topology_Euclidean_Space 

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imports 
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Complex_Main 
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"~~/src/HOL/Library/Countable_Set" 
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"~~/src/HOL/Library/Glbs" 
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"~~/src/HOL/Library/FuncSet" 
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Linear_Algebra 
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Norm_Arith 
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begin 

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lemma dist_0_norm: 
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fixes x :: "'a::real_normed_vector" 

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shows "dist 0 x = norm x" 

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unfolding dist_norm by simp 

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lemma dist_double: "dist x y < d / 2 \<Longrightarrow> dist x z < d / 2 \<Longrightarrow> dist y z < d" 
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using dist_triangle[of y z x] by (simp add: dist_commute) 
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(* LEGACY *) 
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lemma lim_subseq: "subseq r \<Longrightarrow> s > l \<Longrightarrow> (s \<circ> r) > l" 
50972  29 
by (rule LIMSEQ_subseq_LIMSEQ) 
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lemmas real_isGlb_unique = isGlb_unique[where 'a=real] 
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lemma countable_PiE: 
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"finite I \<Longrightarrow> (\<And>i. i \<in> I \<Longrightarrow> countable (F i)) \<Longrightarrow> countable (PiE I F)" 
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by (induct I arbitrary: F rule: finite_induct) (auto simp: PiE_insert_eq) 
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lemma Lim_within_open: 
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fixes f :: "'a::topological_space \<Rightarrow> 'b::topological_space" 
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shows "a \<in> S \<Longrightarrow> open S \<Longrightarrow> (f > l)(at a within S) \<longleftrightarrow> (f > l)(at a)" 
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by (fact tendsto_within_open) 
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lemma continuous_on_union: 
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"closed s \<Longrightarrow> closed t \<Longrightarrow> continuous_on s f \<Longrightarrow> continuous_on t f \<Longrightarrow> continuous_on (s \<union> t) f" 
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by (fact continuous_on_closed_Un) 
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lemma continuous_on_cases: 
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"closed s \<Longrightarrow> closed t \<Longrightarrow> continuous_on s f \<Longrightarrow> continuous_on t g \<Longrightarrow> 
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\<forall>x. (x\<in>s \<and> \<not> P x) \<or> (x \<in> t \<and> P x) \<longrightarrow> f x = g x \<Longrightarrow> 
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continuous_on (s \<union> t) (\<lambda>x. if P x then f x else g x)" 
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by (rule continuous_on_If) auto 
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subsection {* Topological Basis *} 
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context topological_space 

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begin 

57 

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definition "topological_basis B \<longleftrightarrow> 
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(\<forall>b\<in>B. open b) \<and> (\<forall>x. open x \<longrightarrow> (\<exists>B'. B' \<subseteq> B \<and> \<Union>B' = x))" 

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lemma topological_basis: 
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"topological_basis B \<longleftrightarrow> (\<forall>x. open x \<longleftrightarrow> (\<exists>B'. B' \<subseteq> B \<and> \<Union>B' = x))" 
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unfolding topological_basis_def 
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apply safe 

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apply fastforce 

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apply fastforce 

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apply (erule_tac x="x" in allE) 

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apply simp 

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apply (rule_tac x="{x}" in exI) 

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apply auto 

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done 

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lemma topological_basis_iff: 
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assumes "\<And>B'. B' \<in> B \<Longrightarrow> open B'" 

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shows "topological_basis B \<longleftrightarrow> (\<forall>O'. open O' \<longrightarrow> (\<forall>x\<in>O'. \<exists>B'\<in>B. x \<in> B' \<and> B' \<subseteq> O'))" 

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(is "_ \<longleftrightarrow> ?rhs") 

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proof safe 

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fix O' and x::'a 

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assume H: "topological_basis B" "open O'" "x \<in> O'" 

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then have "(\<exists>B'\<subseteq>B. \<Union>B' = O')" by (simp add: topological_basis_def) 
50087  81 
then obtain B' where "B' \<subseteq> B" "O' = \<Union>B'" by auto 
53282  82 
then show "\<exists>B'\<in>B. x \<in> B' \<and> B' \<subseteq> O'" using H by auto 
50087  83 
next 
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assume H: ?rhs 

53282  85 
show "topological_basis B" 
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using assms unfolding topological_basis_def 

50087  87 
proof safe 
53640  88 
fix O' :: "'a set" 
53282  89 
assume "open O'" 
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with H obtain f where "\<forall>x\<in>O'. f x \<in> B \<and> x \<in> f x \<and> f x \<subseteq> O'" 
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by (force intro: bchoice simp: Bex_def) 

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then show "\<exists>B'\<subseteq>B. \<Union>B' = O'" 
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by (auto intro: exI[where x="{f x x. x \<in> O'}"]) 
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qed 

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qed 

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lemma topological_basisI: 

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assumes "\<And>B'. B' \<in> B \<Longrightarrow> open B'" 

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and "\<And>O' x. open O' \<Longrightarrow> x \<in> O' \<Longrightarrow> \<exists>B'\<in>B. x \<in> B' \<and> B' \<subseteq> O'" 
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shows "topological_basis B" 
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using assms by (subst topological_basis_iff) auto 

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lemma topological_basisE: 

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fixes O' 

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assumes "topological_basis B" 

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and "open O'" 
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and "x \<in> O'" 

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obtains B' where "B' \<in> B" "x \<in> B'" "B' \<subseteq> O'" 
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proof atomize_elim 

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from assms have "\<And>B'. B'\<in>B \<Longrightarrow> open B'" 
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by (simp add: topological_basis_def) 

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with topological_basis_iff assms 
53282  113 
show "\<exists>B'. B' \<in> B \<and> x \<in> B' \<and> B' \<subseteq> O'" 
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using assms by (simp add: Bex_def) 

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qed 
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lemma topological_basis_open: 
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assumes "topological_basis B" 
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and "X \<in> B" 
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shows "open X" 
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using assms by (simp add: topological_basis_def) 
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lemma topological_basis_imp_subbasis: 
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assumes B: "topological_basis B" 
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shows "open = generate_topology B" 

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proof (intro ext iffI) 
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fix S :: "'a set" 
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assume "open S" 

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with B obtain B' where "B' \<subseteq> B" "S = \<Union>B'" 
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unfolding topological_basis_def by blast 
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then show "generate_topology B S" 
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by (auto intro: generate_topology.intros dest: topological_basis_open) 
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next 
53255  134 
fix S :: "'a set" 
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assume "generate_topology B S" 

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then show "open S" 

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by induct (auto dest: topological_basis_open[OF B]) 
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qed 
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lemma basis_dense: 
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fixes B :: "'a set set" 
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and f :: "'a set \<Rightarrow> 'a" 

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assumes "topological_basis B" 
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and choosefrom_basis: "\<And>B'. B' \<noteq> {} \<Longrightarrow> f B' \<in> B'" 
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shows "(\<forall>X. open X \<longrightarrow> X \<noteq> {} \<longrightarrow> (\<exists>B' \<in> B. f B' \<in> X))" 
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proof (intro allI impI) 
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fix X :: "'a set" 
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assume "open X" and "X \<noteq> {}" 

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from topological_basisE[OF `topological_basis B` `open X` choosefrom_basis[OF `X \<noteq> {}`]] 
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guess B' . note B' = this 
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then show "\<exists>B'\<in>B. f B' \<in> X" 
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by (auto intro!: choosefrom_basis) 

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qed 
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50087  155 
end 
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lemma topological_basis_prod: 
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assumes A: "topological_basis A" 
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and B: "topological_basis B" 

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shows "topological_basis ((\<lambda>(a, b). a \<times> b) ` (A \<times> B))" 
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unfolding topological_basis_def 
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proof (safe, simp_all del: ex_simps add: subset_image_iff ex_simps(1)[symmetric]) 
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fix S :: "('a \<times> 'b) set" 
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assume "open S" 

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then show "\<exists>X\<subseteq>A \<times> B. (\<Union>(a,b)\<in>X. a \<times> b) = S" 
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proof (safe intro!: exI[of _ "{x\<in>A \<times> B. fst x \<times> snd x \<subseteq> S}"]) 
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fix x y 
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assume "(x, y) \<in> S" 

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from open_prod_elim[OF `open S` this] 
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obtain a b where a: "open a""x \<in> a" and b: "open b" "y \<in> b" and "a \<times> b \<subseteq> S" 
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by (metis mem_Sigma_iff) 
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moreover from topological_basisE[OF A a] guess A0 . 
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moreover from topological_basisE[OF B b] guess B0 . 
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ultimately show "(x, y) \<in> (\<Union>(a, b)\<in>{X \<in> A \<times> B. fst X \<times> snd X \<subseteq> S}. a \<times> b)" 
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by (intro UN_I[of "(A0, B0)"]) auto 
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qed auto 
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qed (metis A B topological_basis_open open_Times) 
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53255  179 

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subsection {* Countable Basis *} 
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locale countable_basis = 
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fixes B :: "'a::topological_space set set" 
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assumes is_basis: "topological_basis B" 
53282  185 
and countable_basis: "countable B" 
33175  186 
begin 
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lemma open_countable_basis_ex: 
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assumes "open X" 
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shows "\<exists>B' \<subseteq> B. X = Union B'" 
53255  191 
using assms countable_basis is_basis 
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unfolding topological_basis_def by blast 

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lemma open_countable_basisE: 
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assumes "open X" 
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obtains B' where "B' \<subseteq> B" "X = Union B'" 
53255  197 
using assms open_countable_basis_ex 
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by (atomize_elim) simp 

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lemma countable_dense_exists: 
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"\<exists>D::'a set. countable D \<and> (\<forall>X. open X \<longrightarrow> X \<noteq> {} \<longrightarrow> (\<exists>d \<in> D. d \<in> X))" 
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proof  
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let ?f = "(\<lambda>B'. SOME x. x \<in> B')" 
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have "countable (?f ` B)" using countable_basis by simp 
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with basis_dense[OF is_basis, of ?f] show ?thesis 
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by (intro exI[where x="?f ` B"]) (metis (mono_tags) all_not_in_conv imageI someI) 
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qed 
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lemma countable_dense_setE: 

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obtains D :: "'a set" 
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where "countable D" "\<And>X. open X \<Longrightarrow> X \<noteq> {} \<Longrightarrow> \<exists>d \<in> D. d \<in> X" 
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using countable_dense_exists by blast 
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end 
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50883  216 
lemma (in first_countable_topology) first_countable_basisE: 
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obtains A where "countable A" "\<And>a. a \<in> A \<Longrightarrow> x \<in> a" "\<And>a. a \<in> A \<Longrightarrow> open a" 

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"\<And>S. open S \<Longrightarrow> x \<in> S \<Longrightarrow> (\<exists>a\<in>A. a \<subseteq> S)" 

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using first_countable_basis[of x] 

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apply atomize_elim 
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apply (elim exE) 

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apply (rule_tac x="range A" in exI) 

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apply auto 

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done 

50883  225 

51105  226 
lemma (in first_countable_topology) first_countable_basis_Int_stableE: 
227 
obtains A where "countable A" "\<And>a. a \<in> A \<Longrightarrow> x \<in> a" "\<And>a. a \<in> A \<Longrightarrow> open a" 

228 
"\<And>S. open S \<Longrightarrow> x \<in> S \<Longrightarrow> (\<exists>a\<in>A. a \<subseteq> S)" 

229 
"\<And>a b. a \<in> A \<Longrightarrow> b \<in> A \<Longrightarrow> a \<inter> b \<in> A" 

230 
proof atomize_elim 

231 
from first_countable_basisE[of x] guess A' . note A' = this 

232 
def A \<equiv> "(\<lambda>N. \<Inter>((\<lambda>n. from_nat_into A' n) ` N)) ` (Collect finite::nat set set)" 

53255  233 
then show "\<exists>A. countable A \<and> (\<forall>a. a \<in> A \<longrightarrow> x \<in> a) \<and> (\<forall>a. a \<in> A \<longrightarrow> open a) \<and> 
51105  234 
(\<forall>S. open S \<longrightarrow> x \<in> S \<longrightarrow> (\<exists>a\<in>A. a \<subseteq> S)) \<and> (\<forall>a b. a \<in> A \<longrightarrow> b \<in> A \<longrightarrow> a \<inter> b \<in> A)" 
235 
proof (safe intro!: exI[where x=A]) 

53255  236 
show "countable A" 
237 
unfolding A_def by (intro countable_image countable_Collect_finite) 

238 
fix a 

239 
assume "a \<in> A" 

240 
then show "x \<in> a" "open a" 

241 
using A'(4)[OF open_UNIV] by (auto simp: A_def intro: A' from_nat_into) 

51105  242 
next 
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243 
let ?int = "\<lambda>N. \<Inter>(from_nat_into A' ` N)" 
53255  244 
fix a b 
245 
assume "a \<in> A" "b \<in> A" 

246 
then obtain N M where "a = ?int N" "b = ?int M" "finite (N \<union> M)" 

247 
by (auto simp: A_def) 

248 
then show "a \<inter> b \<in> A" 

249 
by (auto simp: A_def intro!: image_eqI[where x="N \<union> M"]) 

51105  250 
next 
53255  251 
fix S 
252 
assume "open S" "x \<in> S" 

253 
then obtain a where a: "a\<in>A'" "a \<subseteq> S" using A' by blast 

254 
then show "\<exists>a\<in>A. a \<subseteq> S" using a A' 

51105  255 
by (intro bexI[where x=a]) (auto simp: A_def intro: image_eqI[where x="{to_nat_on A' a}"]) 
256 
qed 

257 
qed 

258 

51473  259 
lemma (in topological_space) first_countableI: 
53255  260 
assumes "countable A" 
261 
and 1: "\<And>a. a \<in> A \<Longrightarrow> x \<in> a" "\<And>a. a \<in> A \<Longrightarrow> open a" 

262 
and 2: "\<And>S. open S \<Longrightarrow> x \<in> S \<Longrightarrow> \<exists>a\<in>A. a \<subseteq> S" 

51473  263 
shows "\<exists>A::nat \<Rightarrow> 'a set. (\<forall>i. x \<in> A i \<and> open (A i)) \<and> (\<forall>S. open S \<and> x \<in> S \<longrightarrow> (\<exists>i. A i \<subseteq> S))" 
264 
proof (safe intro!: exI[of _ "from_nat_into A"]) 

53255  265 
fix i 
51473  266 
have "A \<noteq> {}" using 2[of UNIV] by auto 
53255  267 
show "x \<in> from_nat_into A i" "open (from_nat_into A i)" 
268 
using range_from_nat_into_subset[OF `A \<noteq> {}`] 1 by auto 

269 
next 

270 
fix S 

271 
assume "open S" "x\<in>S" from 2[OF this] 

272 
show "\<exists>i. from_nat_into A i \<subseteq> S" 

273 
using subset_range_from_nat_into[OF `countable A`] by auto 

51473  274 
qed 
51350  275 

50883  276 
instance prod :: (first_countable_topology, first_countable_topology) first_countable_topology 
277 
proof 

278 
fix x :: "'a \<times> 'b" 

279 
from first_countable_basisE[of "fst x"] guess A :: "'a set set" . note A = this 

280 
from first_countable_basisE[of "snd x"] guess B :: "'b set set" . note B = this 

53282  281 
show "\<exists>A::nat \<Rightarrow> ('a \<times> 'b) set. 
282 
(\<forall>i. x \<in> A i \<and> open (A i)) \<and> (\<forall>S. open S \<and> x \<in> S \<longrightarrow> (\<exists>i. A i \<subseteq> S))" 

51473  283 
proof (rule first_countableI[of "(\<lambda>(a, b). a \<times> b) ` (A \<times> B)"], safe) 
53255  284 
fix a b 
285 
assume x: "a \<in> A" "b \<in> B" 

53640  286 
with A(2, 3)[of a] B(2, 3)[of b] show "x \<in> a \<times> b" and "open (a \<times> b)" 
287 
unfolding mem_Times_iff 

288 
by (auto intro: open_Times) 

50883  289 
next 
53255  290 
fix S 
291 
assume "open S" "x \<in> S" 

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292 
from open_prod_elim[OF this] guess a' b' . note a'b' = this 
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293 
moreover from a'b' A(4)[of a'] B(4)[of b'] 
50883  294 
obtain a b where "a \<in> A" "a \<subseteq> a'" "b \<in> B" "b \<subseteq> b'" by auto 
295 
ultimately show "\<exists>a\<in>(\<lambda>(a, b). a \<times> b) ` (A \<times> B). a \<subseteq> S" 

296 
by (auto intro!: bexI[of _ "a \<times> b"] bexI[of _ a] bexI[of _ b]) 

297 
qed (simp add: A B) 

298 
qed 

299 

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300 
class second_countable_topology = topological_space + 
53282  301 
assumes ex_countable_subbasis: 
302 
"\<exists>B::'a::topological_space set set. countable B \<and> open = generate_topology B" 

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303 
begin 
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304 

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305 
lemma ex_countable_basis: "\<exists>B::'a set set. countable B \<and> topological_basis B" 
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306 
proof  
53255  307 
from ex_countable_subbasis obtain B where B: "countable B" "open = generate_topology B" 
308 
by blast 

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309 
let ?B = "Inter ` {b. finite b \<and> b \<subseteq> B }" 
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310 

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311 
show ?thesis 
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312 
proof (intro exI conjI) 
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313 
show "countable ?B" 
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314 
by (intro countable_image countable_Collect_finite_subset B) 
53255  315 
{ 
316 
fix S 

317 
assume "open S" 

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318 
then have "\<exists>B'\<subseteq>{b. finite b \<and> b \<subseteq> B}. (\<Union>b\<in>B'. \<Inter>b) = S" 
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319 
unfolding B 
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320 
proof induct 
53255  321 
case UNIV 
322 
show ?case by (intro exI[of _ "{{}}"]) simp 

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323 
next 
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324 
case (Int a b) 
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325 
then obtain x y where x: "a = UNION x Inter" "\<And>i. i \<in> x \<Longrightarrow> finite i \<and> i \<subseteq> B" 
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326 
and y: "b = UNION y Inter" "\<And>i. i \<in> y \<Longrightarrow> finite i \<and> i \<subseteq> B" 
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327 
by blast 
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328 
show ?case 
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329 
unfolding x y Int_UN_distrib2 
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330 
by (intro exI[of _ "{i \<union> j i j. i \<in> x \<and> j \<in> y}"]) (auto dest: x(2) y(2)) 
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331 
next 
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332 
case (UN K) 
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333 
then have "\<forall>k\<in>K. \<exists>B'\<subseteq>{b. finite b \<and> b \<subseteq> B}. UNION B' Inter = k" by auto 
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334 
then guess k unfolding bchoice_iff .. 
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335 
then show "\<exists>B'\<subseteq>{b. finite b \<and> b \<subseteq> B}. UNION B' Inter = \<Union>K" 
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336 
by (intro exI[of _ "UNION K k"]) auto 
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337 
next 
53255  338 
case (Basis S) 
339 
then show ?case 

51343
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340 
by (intro exI[of _ "{{S}}"]) auto 
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341 
qed 
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342 
then have "(\<exists>B'\<subseteq>Inter ` {b. finite b \<and> b \<subseteq> B}. \<Union>B' = S)" 
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343 
unfolding subset_image_iff by blast } 
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344 
then show "topological_basis ?B" 
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345 
unfolding topological_space_class.topological_basis_def 
53282  346 
by (safe intro!: topological_space_class.open_Inter) 
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347 
(simp_all add: B generate_topology.Basis subset_eq) 
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348 
qed 
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349 
qed 
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350 

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351 
end 
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352 

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353 
sublocale second_countable_topology < 
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354 
countable_basis "SOME B. countable B \<and> topological_basis B" 
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355 
using someI_ex[OF ex_countable_basis] 
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356 
by unfold_locales safe 
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357 

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358 
instance prod :: (second_countable_topology, second_countable_topology) second_countable_topology 
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359 
proof 
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360 
obtain A :: "'a set set" where "countable A" "topological_basis A" 
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361 
using ex_countable_basis by auto 
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362 
moreover 
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363 
obtain B :: "'b set set" where "countable B" "topological_basis B" 
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364 
using ex_countable_basis by auto 
51343
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365 
ultimately show "\<exists>B::('a \<times> 'b) set set. countable B \<and> open = generate_topology B" 
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366 
by (auto intro!: exI[of _ "(\<lambda>(a, b). a \<times> b) ` (A \<times> B)"] topological_basis_prod 
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367 
topological_basis_imp_subbasis) 
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368 
qed 
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369 

50883  370 
instance second_countable_topology \<subseteq> first_countable_topology 
371 
proof 

372 
fix x :: 'a 

373 
def B \<equiv> "SOME B::'a set set. countable B \<and> topological_basis B" 

374 
then have B: "countable B" "topological_basis B" 

375 
using countable_basis is_basis 

376 
by (auto simp: countable_basis is_basis) 

53282  377 
then show "\<exists>A::nat \<Rightarrow> 'a set. 
378 
(\<forall>i. x \<in> A i \<and> open (A i)) \<and> (\<forall>S. open S \<and> x \<in> S \<longrightarrow> (\<exists>i. A i \<subseteq> S))" 

51473  379 
by (intro first_countableI[of "{b\<in>B. x \<in> b}"]) 
380 
(fastforce simp: topological_space_class.topological_basis_def)+ 

50883  381 
qed 
382 

53255  383 

50087  384 
subsection {* Polish spaces *} 
385 

386 
text {* Textbooks define Polish spaces as completely metrizable. 

387 
We assume the topology to be complete for a given metric. *} 

388 

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389 
class polish_space = complete_space + second_countable_topology 
50087  390 

44517  391 
subsection {* General notion of a topology as a value *} 
33175  392 

53255  393 
definition "istopology L \<longleftrightarrow> 
394 
L {} \<and> (\<forall>S T. L S \<longrightarrow> L T \<longrightarrow> L (S \<inter> T)) \<and> (\<forall>K. Ball K L \<longrightarrow> L (\<Union> K))" 

395 

49834  396 
typedef 'a topology = "{L::('a set) \<Rightarrow> bool. istopology L}" 
33175  397 
morphisms "openin" "topology" 
398 
unfolding istopology_def by blast 

399 

400 
lemma istopology_open_in[intro]: "istopology(openin U)" 

401 
using openin[of U] by blast 

402 

403 
lemma topology_inverse': "istopology U \<Longrightarrow> openin (topology U) = U" 

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404 
using topology_inverse[unfolded mem_Collect_eq] . 
33175  405 

406 
lemma topology_inverse_iff: "istopology U \<longleftrightarrow> openin (topology U) = U" 

407 
using topology_inverse[of U] istopology_open_in[of "topology U"] by auto 

408 

409 
lemma topology_eq: "T1 = T2 \<longleftrightarrow> (\<forall>S. openin T1 S \<longleftrightarrow> openin T2 S)" 

53255  410 
proof 
411 
assume "T1 = T2" 

412 
then show "\<forall>S. openin T1 S \<longleftrightarrow> openin T2 S" by simp 

413 
next 

414 
assume H: "\<forall>S. openin T1 S \<longleftrightarrow> openin T2 S" 

415 
then have "openin T1 = openin T2" by (simp add: fun_eq_iff) 

416 
then have "topology (openin T1) = topology (openin T2)" by simp 

417 
then show "T1 = T2" unfolding openin_inverse . 

33175  418 
qed 
419 

420 
text{* Infer the "universe" from union of all sets in the topology. *} 

421 

53640  422 
definition "topspace T = \<Union>{S. openin T S}" 
33175  423 

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424 
subsubsection {* Main properties of open sets *} 
33175  425 

426 
lemma openin_clauses: 

427 
fixes U :: "'a topology" 

53282  428 
shows 
429 
"openin U {}" 

430 
"\<And>S T. openin U S \<Longrightarrow> openin U T \<Longrightarrow> openin U (S\<inter>T)" 

431 
"\<And>K. (\<forall>S \<in> K. openin U S) \<Longrightarrow> openin U (\<Union>K)" 

432 
using openin[of U] unfolding istopology_def mem_Collect_eq by fast+ 

33175  433 

434 
lemma openin_subset[intro]: "openin U S \<Longrightarrow> S \<subseteq> topspace U" 

435 
unfolding topspace_def by blast 

53255  436 

437 
lemma openin_empty[simp]: "openin U {}" 

438 
by (simp add: openin_clauses) 

33175  439 

440 
lemma openin_Int[intro]: "openin U S \<Longrightarrow> openin U T \<Longrightarrow> openin U (S \<inter> T)" 

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441 
using openin_clauses by simp 
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442 

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443 
lemma openin_Union[intro]: "(\<forall>S \<in>K. openin U S) \<Longrightarrow> openin U (\<Union> K)" 
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444 
using openin_clauses by simp 
33175  445 

446 
lemma openin_Un[intro]: "openin U S \<Longrightarrow> openin U T \<Longrightarrow> openin U (S \<union> T)" 

447 
using openin_Union[of "{S,T}" U] by auto 

448 

53255  449 
lemma openin_topspace[intro, simp]: "openin U (topspace U)" 
450 
by (simp add: openin_Union topspace_def) 

33175  451 

49711  452 
lemma openin_subopen: "openin U S \<longleftrightarrow> (\<forall>x \<in> S. \<exists>T. openin U T \<and> x \<in> T \<and> T \<subseteq> S)" 
453 
(is "?lhs \<longleftrightarrow> ?rhs") 

36584  454 
proof 
49711  455 
assume ?lhs 
456 
then show ?rhs by auto 

36584  457 
next 
458 
assume H: ?rhs 

459 
let ?t = "\<Union>{T. openin U T \<and> T \<subseteq> S}" 

460 
have "openin U ?t" by (simp add: openin_Union) 

461 
also have "?t = S" using H by auto 

462 
finally show "openin U S" . 

33175  463 
qed 
464 

49711  465 

44210
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Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

466 
subsubsection {* Closed sets *} 
33175  467 

468 
definition "closedin U S \<longleftrightarrow> S \<subseteq> topspace U \<and> openin U (topspace U  S)" 

469 

53255  470 
lemma closedin_subset: "closedin U S \<Longrightarrow> S \<subseteq> topspace U" 
471 
by (metis closedin_def) 

472 

473 
lemma closedin_empty[simp]: "closedin U {}" 

474 
by (simp add: closedin_def) 

475 

476 
lemma closedin_topspace[intro, simp]: "closedin U (topspace U)" 

477 
by (simp add: closedin_def) 

478 

33175  479 
lemma closedin_Un[intro]: "closedin U S \<Longrightarrow> closedin U T \<Longrightarrow> closedin U (S \<union> T)" 
480 
by (auto simp add: Diff_Un closedin_def) 

481 

53255  482 
lemma Diff_Inter[intro]: "A  \<Inter>S = \<Union> {A  ss. s\<in>S}" 
483 
by auto 

484 

485 
lemma closedin_Inter[intro]: 

486 
assumes Ke: "K \<noteq> {}" 

487 
and Kc: "\<forall>S \<in>K. closedin U S" 

488 
shows "closedin U (\<Inter> K)" 

489 
using Ke Kc unfolding closedin_def Diff_Inter by auto 

33175  490 

491 
lemma closedin_Int[intro]: "closedin U S \<Longrightarrow> closedin U T \<Longrightarrow> closedin U (S \<inter> T)" 

492 
using closedin_Inter[of "{S,T}" U] by auto 

493 

53255  494 
lemma Diff_Diff_Int: "A  (A  B) = A \<inter> B" 
495 
by blast 

496 

33175  497 
lemma openin_closedin_eq: "openin U S \<longleftrightarrow> S \<subseteq> topspace U \<and> closedin U (topspace U  S)" 
498 
apply (auto simp add: closedin_def Diff_Diff_Int inf_absorb2) 

499 
apply (metis openin_subset subset_eq) 

500 
done 

501 

53255  502 
lemma openin_closedin: "S \<subseteq> topspace U \<Longrightarrow> (openin U S \<longleftrightarrow> closedin U (topspace U  S))" 
33175  503 
by (simp add: openin_closedin_eq) 
504 

53255  505 
lemma openin_diff[intro]: 
506 
assumes oS: "openin U S" 

507 
and cT: "closedin U T" 

508 
shows "openin U (S  T)" 

509 
proof  

33175  510 
have "S  T = S \<inter> (topspace U  T)" using openin_subset[of U S] oS cT 
511 
by (auto simp add: topspace_def openin_subset) 

53282  512 
then show ?thesis using oS cT 
513 
by (auto simp add: closedin_def) 

33175  514 
qed 
515 

53255  516 
lemma closedin_diff[intro]: 
517 
assumes oS: "closedin U S" 

518 
and cT: "openin U T" 

519 
shows "closedin U (S  T)" 

520 
proof  

521 
have "S  T = S \<inter> (topspace U  T)" 

53282  522 
using closedin_subset[of U S] oS cT by (auto simp add: topspace_def) 
53255  523 
then show ?thesis 
524 
using oS cT by (auto simp add: openin_closedin_eq) 

525 
qed 

526 

33175  527 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

528 
subsubsection {* Subspace topology *} 
44170
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

529 

510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

530 
definition "subtopology U V = topology (\<lambda>T. \<exists>S. T = S \<inter> V \<and> openin U S)" 
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

531 

510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

532 
lemma istopology_subtopology: "istopology (\<lambda>T. \<exists>S. T = S \<inter> V \<and> openin U S)" 
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

533 
(is "istopology ?L") 
53255  534 
proof  
44170
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

535 
have "?L {}" by blast 
53255  536 
{ 
537 
fix A B 

538 
assume A: "?L A" and B: "?L B" 

539 
from A B obtain Sa and Sb where Sa: "openin U Sa" "A = Sa \<inter> V" and Sb: "openin U Sb" "B = Sb \<inter> V" 

540 
by blast 

541 
have "A \<inter> B = (Sa \<inter> Sb) \<inter> V" "openin U (Sa \<inter> Sb)" 

542 
using Sa Sb by blast+ 

543 
then have "?L (A \<inter> B)" by blast 

544 
} 

33175  545 
moreover 
53255  546 
{ 
53282  547 
fix K 
548 
assume K: "K \<subseteq> Collect ?L" 

44170
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

549 
have th0: "Collect ?L = (\<lambda>S. S \<inter> V) ` Collect (openin U)" 
39302
d7728f65b353
renamed lemmas: ext_iff > fun_eq_iff, set_ext_iff > set_eq_iff, set_ext > set_eqI
nipkow
parents:
39198
diff
changeset

550 
apply (rule set_eqI) 
33175  551 
apply (simp add: Ball_def image_iff) 
53255  552 
apply metis 
553 
done 

33175  554 
from K[unfolded th0 subset_image_iff] 
53255  555 
obtain Sk where Sk: "Sk \<subseteq> Collect (openin U)" "K = (\<lambda>S. S \<inter> V) ` Sk" 
556 
by blast 

557 
have "\<Union>K = (\<Union>Sk) \<inter> V" 

558 
using Sk by auto 

559 
moreover have "openin U (\<Union> Sk)" 

560 
using Sk by (auto simp add: subset_eq) 

561 
ultimately have "?L (\<Union>K)" by blast 

562 
} 

44170
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

563 
ultimately show ?thesis 
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

564 
unfolding subset_eq mem_Collect_eq istopology_def by blast 
33175  565 
qed 
566 

53255  567 
lemma openin_subtopology: "openin (subtopology U V) S \<longleftrightarrow> (\<exists>T. openin U T \<and> S = T \<inter> V)" 
33175  568 
unfolding subtopology_def topology_inverse'[OF istopology_subtopology] 
44170
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

569 
by auto 
33175  570 

53255  571 
lemma topspace_subtopology: "topspace (subtopology U V) = topspace U \<inter> V" 
33175  572 
by (auto simp add: topspace_def openin_subtopology) 
573 

53255  574 
lemma closedin_subtopology: "closedin (subtopology U V) S \<longleftrightarrow> (\<exists>T. closedin U T \<and> S = T \<inter> V)" 
33175  575 
unfolding closedin_def topspace_subtopology 
576 
apply (simp add: openin_subtopology) 

577 
apply (rule iffI) 

578 
apply clarify 

579 
apply (rule_tac x="topspace U  T" in exI) 

53255  580 
apply auto 
581 
done 

33175  582 

583 
lemma openin_subtopology_refl: "openin (subtopology U V) V \<longleftrightarrow> V \<subseteq> topspace U" 

584 
unfolding openin_subtopology 

585 
apply (rule iffI, clarify) 

53255  586 
apply (frule openin_subset[of U]) 
587 
apply blast 

33175  588 
apply (rule exI[where x="topspace U"]) 
49711  589 
apply auto 
590 
done 

591 

592 
lemma subtopology_superset: 

593 
assumes UV: "topspace U \<subseteq> V" 

33175  594 
shows "subtopology U V = U" 
53255  595 
proof  
596 
{ 

597 
fix S 

598 
{ 

599 
fix T 

600 
assume T: "openin U T" "S = T \<inter> V" 

601 
from T openin_subset[OF T(1)] UV have eq: "S = T" 

602 
by blast 

603 
have "openin U S" 

604 
unfolding eq using T by blast 

605 
} 

33175  606 
moreover 
53255  607 
{ 
608 
assume S: "openin U S" 

609 
then have "\<exists>T. openin U T \<and> S = T \<inter> V" 

610 
using openin_subset[OF S] UV by auto 

611 
} 

612 
ultimately have "(\<exists>T. openin U T \<and> S = T \<inter> V) \<longleftrightarrow> openin U S" 

613 
by blast 

614 
} 

615 
then show ?thesis 

616 
unfolding topology_eq openin_subtopology by blast 

33175  617 
qed 
618 

619 
lemma subtopology_topspace[simp]: "subtopology U (topspace U) = U" 

620 
by (simp add: subtopology_superset) 

621 

622 
lemma subtopology_UNIV[simp]: "subtopology U UNIV = U" 

623 
by (simp add: subtopology_superset) 

624 

53255  625 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

626 
subsubsection {* The standard Euclidean topology *} 
33175  627 

53255  628 
definition euclidean :: "'a::topological_space topology" 
629 
where "euclidean = topology open" 

33175  630 

631 
lemma open_openin: "open S \<longleftrightarrow> openin euclidean S" 

632 
unfolding euclidean_def 

633 
apply (rule cong[where x=S and y=S]) 

634 
apply (rule topology_inverse[symmetric]) 

635 
apply (auto simp add: istopology_def) 

44170
510ac30f44c0
make Multivariate_Analysis work with separate set type
huffman
parents:
44167
diff
changeset

636 
done 
33175  637 

638 
lemma topspace_euclidean: "topspace euclidean = UNIV" 

639 
apply (simp add: topspace_def) 

39302
d7728f65b353
renamed lemmas: ext_iff > fun_eq_iff, set_ext_iff > set_eq_iff, set_ext > set_eqI
nipkow
parents:
39198
diff
changeset

640 
apply (rule set_eqI) 
53255  641 
apply (auto simp add: open_openin[symmetric]) 
642 
done 

33175  643 

644 
lemma topspace_euclidean_subtopology[simp]: "topspace (subtopology euclidean S) = S" 

645 
by (simp add: topspace_euclidean topspace_subtopology) 

646 

647 
lemma closed_closedin: "closed S \<longleftrightarrow> closedin euclidean S" 

648 
by (simp add: closed_def closedin_def topspace_euclidean open_openin Compl_eq_Diff_UNIV) 

649 

650 
lemma open_subopen: "open S \<longleftrightarrow> (\<forall>x\<in>S. \<exists>T. open T \<and> x \<in> T \<and> T \<subseteq> S)" 

651 
by (simp add: open_openin openin_subopen[symmetric]) 

652 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

653 
text {* Basic "localization" results are handy for connectedness. *} 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

654 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

655 
lemma openin_open: "openin (subtopology euclidean U) S \<longleftrightarrow> (\<exists>T. open T \<and> (S = U \<inter> T))" 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

656 
by (auto simp add: openin_subtopology open_openin[symmetric]) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

657 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

658 
lemma openin_open_Int[intro]: "open S \<Longrightarrow> openin (subtopology euclidean U) (U \<inter> S)" 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

659 
by (auto simp add: openin_open) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

660 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

661 
lemma open_openin_trans[trans]: 
53255  662 
"open S \<Longrightarrow> open T \<Longrightarrow> T \<subseteq> S \<Longrightarrow> openin (subtopology euclidean S) T" 
44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

663 
by (metis Int_absorb1 openin_open_Int) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

664 

53255  665 
lemma open_subset: "S \<subseteq> T \<Longrightarrow> open S \<Longrightarrow> openin (subtopology euclidean T) S" 
44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

666 
by (auto simp add: openin_open) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

667 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

668 
lemma closedin_closed: "closedin (subtopology euclidean U) S \<longleftrightarrow> (\<exists>T. closed T \<and> S = U \<inter> T)" 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

669 
by (simp add: closedin_subtopology closed_closedin Int_ac) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

670 

53291  671 
lemma closedin_closed_Int: "closed S \<Longrightarrow> closedin (subtopology euclidean U) (U \<inter> S)" 
44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

672 
by (metis closedin_closed) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

673 

53282  674 
lemma closed_closedin_trans: 
675 
"closed S \<Longrightarrow> closed T \<Longrightarrow> T \<subseteq> S \<Longrightarrow> closedin (subtopology euclidean S) T" 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

676 
apply (subgoal_tac "S \<inter> T = T" ) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

677 
apply auto 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

678 
apply (frule closedin_closed_Int[of T S]) 
52624  679 
apply simp 
680 
done 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

681 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

682 
lemma closed_subset: "S \<subseteq> T \<Longrightarrow> closed S \<Longrightarrow> closedin (subtopology euclidean T) S" 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

683 
by (auto simp add: closedin_closed) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

684 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

685 
lemma openin_euclidean_subtopology_iff: 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

686 
fixes S U :: "'a::metric_space set" 
53255  687 
shows "openin (subtopology euclidean U) S \<longleftrightarrow> 
688 
S \<subseteq> U \<and> (\<forall>x\<in>S. \<exists>e>0. \<forall>x'\<in>U. dist x' x < e \<longrightarrow> x'\<in> S)" 

689 
(is "?lhs \<longleftrightarrow> ?rhs") 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

690 
proof 
53255  691 
assume ?lhs 
53282  692 
then show ?rhs 
693 
unfolding openin_open open_dist by blast 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

694 
next 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

695 
def T \<equiv> "{x. \<exists>a\<in>S. \<exists>d>0. (\<forall>y\<in>U. dist y a < d \<longrightarrow> y \<in> S) \<and> dist x a < d}" 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

696 
have 1: "\<forall>x\<in>T. \<exists>e>0. \<forall>y. dist y x < e \<longrightarrow> y \<in> T" 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

697 
unfolding T_def 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

698 
apply clarsimp 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

699 
apply (rule_tac x="d  dist x a" in exI) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

700 
apply (clarsimp simp add: less_diff_eq) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

701 
apply (erule rev_bexI) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

702 
apply (rule_tac x=d in exI, clarify) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

703 
apply (erule le_less_trans [OF dist_triangle]) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

704 
done 
53282  705 
assume ?rhs then have 2: "S = U \<inter> T" 
44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

706 
unfolding T_def 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

707 
apply auto 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

708 
apply (drule (1) bspec, erule rev_bexI) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

709 
apply auto 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

710 
done 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

711 
from 1 2 show ?lhs 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

712 
unfolding openin_open open_dist by fast 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

713 
qed 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

714 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

715 
text {* These "transitivity" results are handy too *} 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

716 

53255  717 
lemma openin_trans[trans]: 
718 
"openin (subtopology euclidean T) S \<Longrightarrow> openin (subtopology euclidean U) T \<Longrightarrow> 

719 
openin (subtopology euclidean U) S" 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

720 
unfolding open_openin openin_open by blast 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

721 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

722 
lemma openin_open_trans: "openin (subtopology euclidean T) S \<Longrightarrow> open T \<Longrightarrow> open S" 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

723 
by (auto simp add: openin_open intro: openin_trans) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

724 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

725 
lemma closedin_trans[trans]: 
53255  726 
"closedin (subtopology euclidean T) S \<Longrightarrow> closedin (subtopology euclidean U) T \<Longrightarrow> 
727 
closedin (subtopology euclidean U) S" 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

728 
by (auto simp add: closedin_closed closed_closedin closed_Inter Int_assoc) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

729 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

730 
lemma closedin_closed_trans: "closedin (subtopology euclidean T) S \<Longrightarrow> closed T \<Longrightarrow> closed S" 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

731 
by (auto simp add: closedin_closed intro: closedin_trans) 
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

732 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

733 

eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

734 
subsection {* Open and closed balls *} 
33175  735 

53255  736 
definition ball :: "'a::metric_space \<Rightarrow> real \<Rightarrow> 'a set" 
737 
where "ball x e = {y. dist x y < e}" 

738 

739 
definition cball :: "'a::metric_space \<Rightarrow> real \<Rightarrow> 'a set" 

740 
where "cball x e = {y. dist x y \<le> e}" 

33175  741 

45776
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

742 
lemma mem_ball [simp]: "y \<in> ball x e \<longleftrightarrow> dist x y < e" 
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

743 
by (simp add: ball_def) 
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

744 

714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

745 
lemma mem_cball [simp]: "y \<in> cball x e \<longleftrightarrow> dist x y \<le> e" 
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

746 
by (simp add: cball_def) 
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

747 

714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

748 
lemma mem_ball_0: 
33175  749 
fixes x :: "'a::real_normed_vector" 
750 
shows "x \<in> ball 0 e \<longleftrightarrow> norm x < e" 

751 
by (simp add: dist_norm) 

752 

45776
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

753 
lemma mem_cball_0: 
33175  754 
fixes x :: "'a::real_normed_vector" 
755 
shows "x \<in> cball 0 e \<longleftrightarrow> norm x \<le> e" 

756 
by (simp add: dist_norm) 

757 

45776
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

758 
lemma centre_in_ball: "x \<in> ball x e \<longleftrightarrow> 0 < e" 
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

759 
by simp 
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

760 

714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

761 
lemma centre_in_cball: "x \<in> cball x e \<longleftrightarrow> 0 \<le> e" 
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

762 
by simp 
714100f5fda4
remove mem_(c)ball_0 and centre_in_(c)ball from simpset, as rules mem_(c)ball always match instead
huffman
parents:
45548
diff
changeset

763 

53255  764 
lemma ball_subset_cball[simp,intro]: "ball x e \<subseteq> cball x e" 
765 
by (simp add: subset_eq) 

766 

53282  767 
lemma subset_ball[intro]: "d \<le> e \<Longrightarrow> ball x d \<subseteq> ball x e" 
53255  768 
by (simp add: subset_eq) 
769 

53282  770 
lemma subset_cball[intro]: "d \<le> e \<Longrightarrow> cball x d \<subseteq> cball x e" 
53255  771 
by (simp add: subset_eq) 
772 

33175  773 
lemma ball_max_Un: "ball a (max r s) = ball a r \<union> ball a s" 
39302
d7728f65b353
renamed lemmas: ext_iff > fun_eq_iff, set_ext_iff > set_eq_iff, set_ext > set_eqI
nipkow
parents:
39198
diff
changeset

774 
by (simp add: set_eq_iff) arith 
33175  775 

776 
lemma ball_min_Int: "ball a (min r s) = ball a r \<inter> ball a s" 

39302
d7728f65b353
renamed lemmas: ext_iff > fun_eq_iff, set_ext_iff > set_eq_iff, set_ext > set_eqI
nipkow
parents:
39198
diff
changeset

777 
by (simp add: set_eq_iff) 
33175  778 

53255  779 
lemma diff_less_iff: 
780 
"(a::real)  b > 0 \<longleftrightarrow> a > b" 

33175  781 
"(a::real)  b < 0 \<longleftrightarrow> a < b" 
53255  782 
"a  b < c \<longleftrightarrow> a < c + b" "a  b > c \<longleftrightarrow> a > c + b" 
783 
by arith+ 

784 

785 
lemma diff_le_iff: 

786 
"(a::real)  b \<ge> 0 \<longleftrightarrow> a \<ge> b" 

787 
"(a::real)  b \<le> 0 \<longleftrightarrow> a \<le> b" 

788 
"a  b \<le> c \<longleftrightarrow> a \<le> c + b" 

789 
"a  b \<ge> c \<longleftrightarrow> a \<ge> c + b" 

790 
by arith+ 

33175  791 

54070  792 
lemma open_vimage: (* TODO: move to Topological_Spaces.thy *) 
793 
assumes "open s" and "continuous_on UNIV f" 

794 
shows "open (vimage f s)" 

795 
using assms unfolding continuous_on_open_vimage [OF open_UNIV] 

796 
by simp 

797 

798 
lemma open_ball [intro, simp]: "open (ball x e)" 

799 
proof  

800 
have "open (dist x ` {..<e})" 

801 
by (intro open_vimage open_lessThan continuous_on_intros) 

802 
also have "dist x ` {..<e} = ball x e" 

803 
by auto 

804 
finally show ?thesis . 

805 
qed 

33175  806 

807 
lemma open_contains_ball: "open S \<longleftrightarrow> (\<forall>x\<in>S. \<exists>e>0. ball x e \<subseteq> S)" 

808 
unfolding open_dist subset_eq mem_ball Ball_def dist_commute .. 

809 

33714
eb2574ac4173
Added new lemmas to Euclidean Space by Robert Himmelmann
hoelzl
parents:
33324
diff
changeset

810 
lemma openE[elim?]: 
53282  811 
assumes "open S" "x\<in>S" 
33714
eb2574ac4173
Added new lemmas to Euclidean Space by Robert Himmelmann
hoelzl
parents:
33324
diff
changeset

812 
obtains e where "e>0" "ball x e \<subseteq> S" 
eb2574ac4173
Added new lemmas to Euclidean Space by Robert Himmelmann
hoelzl
parents:
33324
diff
changeset

813 
using assms unfolding open_contains_ball by auto 
eb2574ac4173
Added new lemmas to Euclidean Space by Robert Himmelmann
hoelzl
parents:
33324
diff
changeset

814 

33175  815 
lemma open_contains_ball_eq: "open S \<Longrightarrow> \<forall>x. x\<in>S \<longleftrightarrow> (\<exists>e>0. ball x e \<subseteq> S)" 
816 
by (metis open_contains_ball subset_eq centre_in_ball) 

817 

818 
lemma ball_eq_empty[simp]: "ball x e = {} \<longleftrightarrow> e \<le> 0" 

39302
d7728f65b353
renamed lemmas: ext_iff > fun_eq_iff, set_ext_iff > set_eq_iff, set_ext > set_eqI
nipkow
parents:
39198
diff
changeset

819 
unfolding mem_ball set_eq_iff 
33175  820 
apply (simp add: not_less) 
52624  821 
apply (metis zero_le_dist order_trans dist_self) 
822 
done 

33175  823 

53291  824 
lemma ball_empty[intro]: "e \<le> 0 \<Longrightarrow> ball x e = {}" by simp 
33175  825 

50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

826 
lemma euclidean_dist_l2: 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

827 
fixes x y :: "'a :: euclidean_space" 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

828 
shows "dist x y = setL2 (\<lambda>i. dist (x \<bullet> i) (y \<bullet> i)) Basis" 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

829 
unfolding dist_norm norm_eq_sqrt_inner setL2_def 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

830 
by (subst euclidean_inner) (simp add: power2_eq_square inner_diff_left) 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

831 

899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

832 
definition "box a b = {x. \<forall>i\<in>Basis. a \<bullet> i < x \<bullet> i \<and> x \<bullet> i < b \<bullet> i}" 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

833 

50087  834 
lemma rational_boxes: 
50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

835 
fixes x :: "'a\<Colon>euclidean_space" 
53291  836 
assumes "e > 0" 
50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

837 
shows "\<exists>a b. (\<forall>i\<in>Basis. a \<bullet> i \<in> \<rat> \<and> b \<bullet> i \<in> \<rat> ) \<and> x \<in> box a b \<and> box a b \<subseteq> ball x e" 
50087  838 
proof  
839 
def e' \<equiv> "e / (2 * sqrt (real (DIM ('a))))" 

53291  840 
then have e: "e' > 0" 
53255  841 
using assms by (auto intro!: divide_pos_pos simp: DIM_positive) 
50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

842 
have "\<forall>i. \<exists>y. y \<in> \<rat> \<and> y < x \<bullet> i \<and> x \<bullet> i  y < e'" (is "\<forall>i. ?th i") 
50087  843 
proof 
53255  844 
fix i 
845 
from Rats_dense_in_real[of "x \<bullet> i  e'" "x \<bullet> i"] e 

846 
show "?th i" by auto 

50087  847 
qed 
848 
from choice[OF this] guess a .. note a = this 

50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

849 
have "\<forall>i. \<exists>y. y \<in> \<rat> \<and> x \<bullet> i < y \<and> y  x \<bullet> i < e'" (is "\<forall>i. ?th i") 
50087  850 
proof 
53255  851 
fix i 
852 
from Rats_dense_in_real[of "x \<bullet> i" "x \<bullet> i + e'"] e 

853 
show "?th i" by auto 

50087  854 
qed 
855 
from choice[OF this] guess b .. note b = this 

50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

856 
let ?a = "\<Sum>i\<in>Basis. a i *\<^sub>R i" and ?b = "\<Sum>i\<in>Basis. b i *\<^sub>R i" 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

857 
show ?thesis 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

858 
proof (rule exI[of _ ?a], rule exI[of _ ?b], safe) 
53255  859 
fix y :: 'a 
860 
assume *: "y \<in> box ?a ?b" 

53015
a1119cf551e8
standardized symbols via "isabelle update_sub_sup", excluding src/Pure and src/Tools/WWW_Find;
wenzelm
parents:
52625
diff
changeset

861 
have "dist x y = sqrt (\<Sum>i\<in>Basis. (dist (x \<bullet> i) (y \<bullet> i))\<^sup>2)" 
50087  862 
unfolding setL2_def[symmetric] by (rule euclidean_dist_l2) 
50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

863 
also have "\<dots> < sqrt (\<Sum>(i::'a)\<in>Basis. e^2 / real (DIM('a)))" 
50087  864 
proof (rule real_sqrt_less_mono, rule setsum_strict_mono) 
53255  865 
fix i :: "'a" 
866 
assume i: "i \<in> Basis" 

867 
have "a i < y\<bullet>i \<and> y\<bullet>i < b i" 

868 
using * i by (auto simp: box_def) 

869 
moreover have "a i < x\<bullet>i" "x\<bullet>i  a i < e'" 

870 
using a by auto 

871 
moreover have "x\<bullet>i < b i" "b i  x\<bullet>i < e'" 

872 
using b by auto 

873 
ultimately have "\<bar>x\<bullet>i  y\<bullet>i\<bar> < 2 * e'" 

874 
by auto 

50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

875 
then have "dist (x \<bullet> i) (y \<bullet> i) < e/sqrt (real (DIM('a)))" 
50087  876 
unfolding e'_def by (auto simp: dist_real_def) 
53015
a1119cf551e8
standardized symbols via "isabelle update_sub_sup", excluding src/Pure and src/Tools/WWW_Find;
wenzelm
parents:
52625
diff
changeset

877 
then have "(dist (x \<bullet> i) (y \<bullet> i))\<^sup>2 < (e/sqrt (real (DIM('a))))\<^sup>2" 
50087  878 
by (rule power_strict_mono) auto 
53015
a1119cf551e8
standardized symbols via "isabelle update_sub_sup", excluding src/Pure and src/Tools/WWW_Find;
wenzelm
parents:
52625
diff
changeset

879 
then show "(dist (x \<bullet> i) (y \<bullet> i))\<^sup>2 < e\<^sup>2 / real DIM('a)" 
50087  880 
by (simp add: power_divide) 
881 
qed auto 

53255  882 
also have "\<dots> = e" 
883 
using `0 < e` by (simp add: real_eq_of_nat) 

884 
finally show "y \<in> ball x e" 

885 
by (auto simp: ball_def) 

50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

886 
qed (insert a b, auto simp: box_def) 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

887 
qed 
51103  888 

50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

889 
lemma open_UNION_box: 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

890 
fixes M :: "'a\<Colon>euclidean_space set" 
53282  891 
assumes "open M" 
50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

892 
defines "a' \<equiv> \<lambda>f :: 'a \<Rightarrow> real \<times> real. (\<Sum>(i::'a)\<in>Basis. fst (f i) *\<^sub>R i)" 
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

893 
defines "b' \<equiv> \<lambda>f :: 'a \<Rightarrow> real \<times> real. (\<Sum>(i::'a)\<in>Basis. snd (f i) *\<^sub>R i)" 
53015
a1119cf551e8
standardized symbols via "isabelle update_sub_sup", excluding src/Pure and src/Tools/WWW_Find;
wenzelm
parents:
52625
diff
changeset

894 
defines "I \<equiv> {f\<in>Basis \<rightarrow>\<^sub>E \<rat> \<times> \<rat>. box (a' f) (b' f) \<subseteq> M}" 
50526
899c9c4e4a4c
Remove the indexed basis from the definition of euclidean spaces and only use the set of Basis vectors
hoelzl
parents:
50324
diff
changeset

895 
shows "M = (\<Union>f\<in>I. box (a' f) (b' f))" 
52624  896 
proof  
897 
{ 

898 
fix x assume "x \<in> M" 

899 
obtain e where e: "e > 0" "ball x e \<subseteq> M" 

900 
using openE[OF `open M` `x \<in> M`] by auto 

53282  901 
moreover obtain a b where ab: 
902 
"x \<in> box a b" 

903 
"\<forall>i \<in> Basis. a \<bullet> i \<in> \<rat>" 

904 
"\<forall>i\<in>Basis. b \<bullet> i \<in> \<rat>" 

905 
"box a b \<subseteq> ball x e" 

52624  906 
using rational_boxes[OF e(1)] by metis 
907 
ultimately have "x \<in> (\<Union>f\<in>I. box (a' f) (b' f))" 

908 
by (intro UN_I[of "\<lambda>i\<in>Basis. (a \<bullet> i, b \<bullet> i)"]) 

909 
(auto simp: euclidean_representation I_def a'_def b'_def) 

910 
} 

911 
then show ?thesis by (auto simp: I_def) 

912 
qed 

913 

33175  914 

915 
subsection{* Connectedness *} 

916 

917 
lemma connected_local: 

53255  918 
"connected S \<longleftrightarrow> 
919 
\<not> (\<exists>e1 e2. 

920 
openin (subtopology euclidean S) e1 \<and> 

921 
openin (subtopology euclidean S) e2 \<and> 

922 
S \<subseteq> e1 \<union> e2 \<and> 

923 
e1 \<inter> e2 = {} \<and> 

924 
e1 \<noteq> {} \<and> 

925 
e2 \<noteq> {})" 

53282  926 
unfolding connected_def openin_open 
927 
apply safe 

928 
apply blast+ 

929 
done 

33175  930 

34105  931 
lemma exists_diff: 
932 
fixes P :: "'a set \<Rightarrow> bool" 

933 
shows "(\<exists>S. P( S)) \<longleftrightarrow> (\<exists>S. P S)" (is "?lhs \<longleftrightarrow> ?rhs") 

53255  934 
proof  
935 
{ 

936 
assume "?lhs" 

937 
then have ?rhs by blast 

938 
} 

33175  939 
moreover 
53255  940 
{ 
941 
fix S 

942 
assume H: "P S" 

34105  943 
have "S =  ( S)" by auto 
53255  944 
with H have "P ( ( S))" by metis 
945 
} 

33175  946 
ultimately show ?thesis by metis 
947 
qed 

948 

949 
lemma connected_clopen: "connected S \<longleftrightarrow> 

53255  950 
(\<forall>T. openin (subtopology euclidean S) T \<and> 
951 
closedin (subtopology euclidean S) T \<longrightarrow> T = {} \<or> T = S)" (is "?lhs \<longleftrightarrow> ?rhs") 

952 
proof  

953 
have "\<not> connected S \<longleftrightarrow> 

954 
(\<exists>e1 e2. open e1 \<and> open ( e2) \<and> S \<subseteq> e1 \<union> ( e2) \<and> e1 \<inter> ( e2) \<inter> S = {} \<and> e1 \<inter> S \<noteq> {} \<and> ( e2) \<inter> S \<noteq> {})" 

33175  955 
unfolding connected_def openin_open closedin_closed 
52624  956 
apply (subst exists_diff) 
957 
apply blast 

958 
done 

53282  959 
then have th0: "connected S \<longleftrightarrow> 
53255  960 
\<not> (\<exists>e2 e1. closed e2 \<and> open e1 \<and> S \<subseteq> e1 \<union> ( e2) \<and> e1 \<inter> ( e2) \<inter> S = {} \<and> e1 \<inter> S \<noteq> {} \<and> ( e2) \<inter> S \<noteq> {})" 
52624  961 
(is " _ \<longleftrightarrow> \<not> (\<exists>e2 e1. ?P e2 e1)") 
962 
apply (simp add: closed_def) 

963 
apply metis 

964 
done 

33175  965 
have th1: "?rhs \<longleftrightarrow> \<not> (\<exists>t' t. closed t'\<and>t = S\<inter>t' \<and> t\<noteq>{} \<and> t\<noteq>S \<and> (\<exists>t'. open t' \<and> t = S \<inter> t'))" 
966 
(is "_ \<longleftrightarrow> \<not> (\<exists>t' t. ?Q t' t)") 

967 
unfolding connected_def openin_open closedin_closed by auto 

53255  968 
{ 
969 
fix e2 

970 
{ 

971 
fix e1 

53282  972 
have "?P e2 e1 \<longleftrightarrow> (\<exists>t. closed e2 \<and> t = S\<inter>e2 \<and> open e1 \<and> t = S\<inter>e1 \<and> t\<noteq>{} \<and> t \<noteq> S)" 
53255  973 
by auto 
974 
} 

975 
then have "(\<exists>e1. ?P e2 e1) \<longleftrightarrow> (\<exists>t. ?Q e2 t)" 

976 
by metis 

977 
} 

978 
then have "\<forall>e2. (\<exists>e1. ?P e2 e1) \<longleftrightarrow> (\<exists>t. ?Q e2 t)" 

979 
by blast 

980 
then show ?thesis 

981 
unfolding th0 th1 by simp 

33175  982 
qed 
983 

44210
eba74571833b
Topology_Euclidean_Space.thy: organize section headings
huffman
parents:
44207
diff
changeset

984 

33175  985 
subsection{* Limit points *} 
986 

53282  987 
definition (in topological_space) islimpt:: "'a \<Rightarrow> 'a set \<Rightarrow> bool" (infixr "islimpt" 60) 
53255  988 
where "x islimpt S \<longleftrightarrow> (\<forall>T. x\<in>T \<longrightarrow> open T \<longrightarrow> (\<exists>y\<in>S. y\<in>T \<and> y\<noteq>x))" 
33175  989 

990 
lemma islimptI: 

991 
assumes "\<And>T. x \<in> T \<Longrightarrow> open T \<Longrightarrow> \<exists>y\<in>S. y \<in> T \<and> y \<noteq> x" 

992 
shows "x islimpt S" 

993 
using assms unfolding islimpt_def by auto 

994 

995 
lemma islimptE: 

996 
assumes "x islimpt S" and "x \<in> T" and "open T" 

997 
obtains y where "y \<in> S" and "y \<in> T" and "y \<noteq> x" 

998 
using assms unfolding islimpt_def by auto 

999 

44584  1000 
lemma islimpt_iff_eventually: "x islimpt S \<longleftrightarrow> \<not> eventually (\<lambda>y. y \<notin> S) (at x)" 
1001 
unfolding islimpt_def eventually_at_topological by auto 

1002 

53255  1003 
lemma islimpt_subset: "x islimpt S \<Longrightarrow> S \<subseteq> T \<Longrightarrow> x islimpt T" 
44584  1004 
unfolding islimpt_def by fast 
33175  1005 

1006 
lemma islimpt_approachable: 

1007 
fixes x :: "'a::metric_space" 

1008 
shows "x islimpt S \<longleftrightarrow> (\<forall>e>0. \<exists>x'\<in>S. x' \<noteq> x \<and> dist x' x < e)" 

44584  1009 
unfolding islimpt_iff_eventually eventually_at by fast 
33175  1010 

1011 
lemma islimpt_approachable_le: 

1012 
fixes x :: "'a::metric_space" 

53640  1013 
shows "x islimpt S \<longleftrightarrow> (\<forall>e>0. \<exists>x'\<in> S. x' \<noteq> x \<and> dist x' x \<le> e)" 
33175  1014 
unfolding islimpt_approachable 
44584  1015 
using approachable_lt_le [where f="\<lambda>y. dist y x" and P="\<lambda>y. y \<notin> S \<or> y = x", 
1016 
THEN arg_cong [where f=Not]] 

1017 
by (simp add: Bex_def conj_commute conj_left_commute) 

33175  1018 

44571  1019 
lemma islimpt_UNIV_iff: "x islimpt UNIV \<longleftrightarrow> \<not> open {x}" 
1020 
unfolding islimpt_def by (safe, fast, case_tac "T = {x}", fast, fast) 

1021 

51351  1022 
lemma islimpt_punctured: "x islimpt S = x islimpt (S{x})" 
1023 
unfolding islimpt_def by blast 

1024 

44210
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1025 
text {* A perfect space has no isolated points. *} 
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1026 

44571  1027 
lemma islimpt_UNIV [simp, intro]: "(x::'a::perfect_space) islimpt UNIV" 
1028 
unfolding islimpt_UNIV_iff by (rule not_open_singleton) 

33175  1029 

1030 
lemma perfect_choose_dist: 

44072
5b970711fb39
class perfect_space inherits from topological_space;
huffman
parents:
43338
diff
changeset

1031 
fixes x :: "'a::{perfect_space, metric_space}" 
33175  1032 
shows "0 < r \<Longrightarrow> \<exists>a. a \<noteq> x \<and> dist a x < r" 
53255  1033 
using islimpt_UNIV [of x] 
1034 
by (simp add: islimpt_approachable) 

33175  1035 

1036 
lemma closed_limpt: "closed S \<longleftrightarrow> (\<forall>x. x islimpt S \<longrightarrow> x \<in> S)" 

1037 
unfolding closed_def 

1038 
apply (subst open_subopen) 

34105  1039 
apply (simp add: islimpt_def subset_eq) 
52624  1040 
apply (metis ComplE ComplI) 
1041 
done 

33175  1042 

1043 
lemma islimpt_EMPTY[simp]: "\<not> x islimpt {}" 

1044 
unfolding islimpt_def by auto 

1045 

1046 
lemma finite_set_avoid: 

1047 
fixes a :: "'a::metric_space" 

53255  1048 
assumes fS: "finite S" 
53640  1049 
shows "\<exists>d>0. \<forall>x\<in>S. x \<noteq> a \<longrightarrow> d \<le> dist a x" 
53255  1050 
proof (induct rule: finite_induct[OF fS]) 
1051 
case 1 

1052 
then show ?case by (auto intro: zero_less_one) 

33175  1053 
next 
1054 
case (2 x F) 

53255  1055 
from 2 obtain d where d: "d >0" "\<forall>x\<in>F. x\<noteq>a \<longrightarrow> d \<le> dist a x" 
1056 
by blast 

1057 
show ?case 

1058 
proof (cases "x = a") 

1059 
case True 

1060 
then show ?thesis using d by auto 

1061 
next 

1062 
case False 

33175  1063 
let ?d = "min d (dist a x)" 
53255  1064 
have dp: "?d > 0" 
1065 
using False d(1) using dist_nz by auto 

1066 
from d have d': "\<forall>x\<in>F. x\<noteq>a \<longrightarrow> ?d \<le> dist a x" 

1067 
by auto 

1068 
with dp False show ?thesis 

1069 
by (auto intro!: exI[where x="?d"]) 

1070 
qed 

33175  1071 
qed 
1072 

1073 
lemma islimpt_Un: "x islimpt (S \<union> T) \<longleftrightarrow> x islimpt S \<or> x islimpt T" 

50897
078590669527
generalize lemma islimpt_finite to class t1_space
huffman
parents:
50884
diff
changeset

1074 
by (simp add: islimpt_iff_eventually eventually_conj_iff) 
33175  1075 

1076 
lemma discrete_imp_closed: 

1077 
fixes S :: "'a::metric_space set" 

53255  1078 
assumes e: "0 < e" 
1079 
and d: "\<forall>x \<in> S. \<forall>y \<in> S. dist y x < e \<longrightarrow> y = x" 

33175  1080 
shows "closed S" 
53255  1081 
proof  
1082 
{ 

1083 
fix x 

1084 
assume C: "\<forall>e>0. \<exists>x'\<in>S. x' \<noteq> x \<and> dist x' x < e" 

33175  1085 
from e have e2: "e/2 > 0" by arith 
53282  1086 
from C[rule_format, OF e2] obtain y where y: "y \<in> S" "y \<noteq> x" "dist y x < e/2" 
53255  1087 
by blast 
33175  1088 
let ?m = "min (e/2) (dist x y) " 
53255  1089 
from e2 y(2) have mp: "?m > 0" 
53291  1090 
by (simp add: dist_nz[symmetric]) 
53282  1091 
from C[rule_format, OF mp] obtain z where z: "z \<in> S" "z \<noteq> x" "dist z x < ?m" 
53255  1092 
by blast 
33175  1093 
have th: "dist z y < e" using z y 
1094 
by (intro dist_triangle_lt [where z=x], simp) 

1095 
from d[rule_format, OF y(1) z(1) th] y z 

1096 
have False by (auto simp add: dist_commute)} 

53255  1097 
then show ?thesis 
1098 
by (metis islimpt_approachable closed_limpt [where 'a='a]) 

33175  1099 
qed 
1100 

44210
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1101 

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1102 
subsection {* Interior of a Set *} 
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1103 

44519  1104 
definition "interior S = \<Union>{T. open T \<and> T \<subseteq> S}" 
1105 

1106 
lemma interiorI [intro?]: 

1107 
assumes "open T" and "x \<in> T" and "T \<subseteq> S" 

1108 
shows "x \<in> interior S" 

1109 
using assms unfolding interior_def by fast 

1110 

1111 
lemma interiorE [elim?]: 

1112 
assumes "x \<in> interior S" 

1113 
obtains T where "open T" and "x \<in> T" and "T \<subseteq> S" 

1114 
using assms unfolding interior_def by fast 

1115 

1116 
lemma open_interior [simp, intro]: "open (interior S)" 

1117 
by (simp add: interior_def open_Union) 

1118 

1119 
lemma interior_subset: "interior S \<subseteq> S" 

1120 
by (auto simp add: interior_def) 

1121 

1122 
lemma interior_maximal: "T \<subseteq> S \<Longrightarrow> open T \<Longrightarrow> T \<subseteq> interior S" 

1123 
by (auto simp add: interior_def) 

1124 

1125 
lemma interior_open: "open S \<Longrightarrow> interior S = S" 

1126 
by (intro equalityI interior_subset interior_maximal subset_refl) 

33175  1127 

1128 
lemma interior_eq: "interior S = S \<longleftrightarrow> open S" 

44519  1129 
by (metis open_interior interior_open) 
1130 

1131 
lemma open_subset_interior: "open S \<Longrightarrow> S \<subseteq> interior T \<longleftrightarrow> S \<subseteq> T" 

33175  1132 
by (metis interior_maximal interior_subset subset_trans) 
1133 

44519  1134 
lemma interior_empty [simp]: "interior {} = {}" 
1135 
using open_empty by (rule interior_open) 

1136 

44522
2f7e9d890efe
rename subset_{interior,closure} to {interior,closure}_mono;
huffman
parents:
44519
diff
changeset

1137 
lemma interior_UNIV [simp]: "interior UNIV = UNIV" 
2f7e9d890efe
rename subset_{interior,closure} to {interior,closure}_mono;
huffman
parents:
44519
diff
changeset

1138 
using open_UNIV by (rule interior_open) 
2f7e9d890efe
rename subset_{interior,closure} to {interior,closure}_mono;
huffman
parents:
44519
diff
changeset

1139 

44519  1140 
lemma interior_interior [simp]: "interior (interior S) = interior S" 
1141 
using open_interior by (rule interior_open) 

1142 

44522
2f7e9d890efe
rename subset_{interior,closure} to {interior,closure}_mono;
huffman
parents:
44519
diff
changeset

1143 
lemma interior_mono: "S \<subseteq> T \<Longrightarrow> interior S \<subseteq> interior T" 
2f7e9d890efe
rename subset_{interior,closure} to {interior,closure}_mono;
huffman
parents:
44519
diff
changeset

1144 
by (auto simp add: interior_def) 
44519  1145 
