section \<open>Contour integration\<close>
theory Contour_Integration
imports "HOL-Analysis.Analysis"
begin
lemma lhopital_complex_simple:
assumes "(f has_field_derivative f') (at z)"
assumes "(g has_field_derivative g') (at z)"
assumes "f z = 0" "g z = 0" "g' \<noteq> 0" "f' / g' = c"
shows "((\<lambda>w. f w / g w) \<longlongrightarrow> c) (at z)"
proof -
have "eventually (\<lambda>w. w \<noteq> z) (at z)"
by (auto simp: eventually_at_filter)
hence "eventually (\<lambda>w. ((f w - f z) / (w - z)) / ((g w - g z) / (w - z)) = f w / g w) (at z)"
by eventually_elim (simp add: assms field_split_simps)
moreover have "((\<lambda>w. ((f w - f z) / (w - z)) / ((g w - g z) / (w - z))) \<longlongrightarrow> f' / g') (at z)"
by (intro tendsto_divide has_field_derivativeD assms)
ultimately have "((\<lambda>w. f w / g w) \<longlongrightarrow> f' / g') (at z)"
by (blast intro: Lim_transform_eventually)
with assms show ?thesis by simp
qed
subsection\<open>Definition\<close>
text\<open>
This definition is for complex numbers only, and does not generalise to
line integrals in a vector field
\<close>
definition\<^marker>\<open>tag important\<close> has_contour_integral :: "(complex \<Rightarrow> complex) \<Rightarrow> complex \<Rightarrow> (real \<Rightarrow> complex) \<Rightarrow> bool"
(infixr "has'_contour'_integral" 50)
where "(f has_contour_integral i) g \<equiv>
((\<lambda>x. f(g x) * vector_derivative g (at x within {0..1}))
has_integral i) {0..1}"
definition\<^marker>\<open>tag important\<close> contour_integrable_on
(infixr "contour'_integrable'_on" 50)
where "f contour_integrable_on g \<equiv> \<exists>i. (f has_contour_integral i) g"
definition\<^marker>\<open>tag important\<close> contour_integral
where "contour_integral g f \<equiv> SOME i. (f has_contour_integral i) g \<or> \<not> f contour_integrable_on g \<and> i=0"
lemma not_integrable_contour_integral: "\<not> f contour_integrable_on g \<Longrightarrow> contour_integral g f = 0"
unfolding contour_integrable_on_def contour_integral_def by blast
lemma contour_integral_unique: "(f has_contour_integral i) g \<Longrightarrow> contour_integral g f = i"
apply (simp add: contour_integral_def has_contour_integral_def contour_integrable_on_def)
using has_integral_unique by blast
lemma has_contour_integral_eqpath:
"\<lbrakk>(f has_contour_integral y) p; f contour_integrable_on \<gamma>;
contour_integral p f = contour_integral \<gamma> f\<rbrakk>
\<Longrightarrow> (f has_contour_integral y) \<gamma>"
using contour_integrable_on_def contour_integral_unique by auto
lemma has_contour_integral_integral:
"f contour_integrable_on i \<Longrightarrow> (f has_contour_integral (contour_integral i f)) i"
by (metis contour_integral_unique contour_integrable_on_def)
lemma has_contour_integral_unique:
"(f has_contour_integral i) g \<Longrightarrow> (f has_contour_integral j) g \<Longrightarrow> i = j"
using has_integral_unique
by (auto simp: has_contour_integral_def)
lemma has_contour_integral_integrable: "(f has_contour_integral i) g \<Longrightarrow> f contour_integrable_on g"
using contour_integrable_on_def by blast
text\<open>Show that we can forget about the localized derivative.\<close>
lemma has_integral_localized_vector_derivative:
"((\<lambda>x. f (g x) * vector_derivative g (at x within {a..b})) has_integral i) {a..b} \<longleftrightarrow>
((\<lambda>x. f (g x) * vector_derivative g (at x)) has_integral i) {a..b}"
proof -
have *: "{a..b} - {a,b} = interior {a..b}"
by (simp add: atLeastAtMost_diff_ends)
show ?thesis
apply (rule has_integral_spike_eq [of "{a,b}"])
apply (auto simp: at_within_interior [of _ "{a..b}"])
done
qed
lemma integrable_on_localized_vector_derivative:
"(\<lambda>x. f (g x) * vector_derivative g (at x within {a..b})) integrable_on {a..b} \<longleftrightarrow>
(\<lambda>x. f (g x) * vector_derivative g (at x)) integrable_on {a..b}"
by (simp add: integrable_on_def has_integral_localized_vector_derivative)
lemma has_contour_integral:
"(f has_contour_integral i) g \<longleftrightarrow>
((\<lambda>x. f (g x) * vector_derivative g (at x)) has_integral i) {0..1}"
by (simp add: has_integral_localized_vector_derivative has_contour_integral_def)
lemma contour_integrable_on:
"f contour_integrable_on g \<longleftrightarrow>
(\<lambda>t. f(g t) * vector_derivative g (at t)) integrable_on {0..1}"
by (simp add: has_contour_integral integrable_on_def contour_integrable_on_def)
subsection\<^marker>\<open>tag unimportant\<close> \<open>Reversing a path\<close>
lemma has_contour_integral_reversepath:
assumes "valid_path g" and f: "(f has_contour_integral i) g"
shows "(f has_contour_integral (-i)) (reversepath g)"
proof -
{ fix S x
assume xs: "g C1_differentiable_on ({0..1} - S)" "x \<notin> (-) 1 ` S" "0 \<le> x" "x \<le> 1"
have "vector_derivative (\<lambda>x. g (1 - x)) (at x within {0..1}) =
- vector_derivative g (at (1 - x) within {0..1})"
proof -
obtain f' where f': "(g has_vector_derivative f') (at (1 - x))"
using xs
by (force simp: has_vector_derivative_def C1_differentiable_on_def)
have "(g \<circ> (\<lambda>x. 1 - x) has_vector_derivative -1 *\<^sub>R f') (at x)"
by (intro vector_diff_chain_within has_vector_derivative_at_within [OF f'] derivative_eq_intros | simp)+
then have mf': "((\<lambda>x. g (1 - x)) has_vector_derivative -f') (at x)"
by (simp add: o_def)
show ?thesis
using xs
by (auto simp: vector_derivative_at_within_ivl [OF mf'] vector_derivative_at_within_ivl [OF f'])
qed
} note * = this
obtain S where S: "continuous_on {0..1} g" "finite S" "g C1_differentiable_on {0..1} - S"
using assms by (auto simp: valid_path_def piecewise_C1_differentiable_on_def)
have "((\<lambda>x. - (f (g (1 - x)) * vector_derivative g (at (1 - x) within {0..1}))) has_integral -i)
{0..1}"
using has_integral_affinity01 [where m= "-1" and c=1, OF f [unfolded has_contour_integral_def]]
by (simp add: has_integral_neg)
then show ?thesis
using S
apply (clarsimp simp: reversepath_def has_contour_integral_def)
apply (rule_tac S = "(\<lambda>x. 1 - x) ` S" in has_integral_spike_finite)
apply (auto simp: *)
done
qed
lemma contour_integrable_reversepath:
"valid_path g \<Longrightarrow> f contour_integrable_on g \<Longrightarrow> f contour_integrable_on (reversepath g)"
using has_contour_integral_reversepath contour_integrable_on_def by blast
lemma contour_integrable_reversepath_eq:
"valid_path g \<Longrightarrow> (f contour_integrable_on (reversepath g) \<longleftrightarrow> f contour_integrable_on g)"
using contour_integrable_reversepath valid_path_reversepath by fastforce
lemma contour_integral_reversepath:
assumes "valid_path g"
shows "contour_integral (reversepath g) f = - (contour_integral g f)"
proof (cases "f contour_integrable_on g")
case True then show ?thesis
by (simp add: assms contour_integral_unique has_contour_integral_integral has_contour_integral_reversepath)
next
case False then have "\<not> f contour_integrable_on (reversepath g)"
by (simp add: assms contour_integrable_reversepath_eq)
with False show ?thesis by (simp add: not_integrable_contour_integral)
qed
subsection\<^marker>\<open>tag unimportant\<close> \<open>Joining two paths together\<close>
lemma has_contour_integral_join:
assumes "(f has_contour_integral i1) g1" "(f has_contour_integral i2) g2"
"valid_path g1" "valid_path g2"
shows "(f has_contour_integral (i1 + i2)) (g1 +++ g2)"
proof -
obtain s1 s2
where s1: "finite s1" "\<forall>x\<in>{0..1} - s1. g1 differentiable at x"
and s2: "finite s2" "\<forall>x\<in>{0..1} - s2. g2 differentiable at x"
using assms
by (auto simp: valid_path_def piecewise_C1_differentiable_on_def C1_differentiable_on_eq)
have 1: "((\<lambda>x. f (g1 x) * vector_derivative g1 (at x)) has_integral i1) {0..1}"
and 2: "((\<lambda>x. f (g2 x) * vector_derivative g2 (at x)) has_integral i2) {0..1}"
using assms
by (auto simp: has_contour_integral)
have i1: "((\<lambda>x. (2*f (g1 (2*x))) * vector_derivative g1 (at (2*x))) has_integral i1) {0..1/2}"
and i2: "((\<lambda>x. (2*f (g2 (2*x - 1))) * vector_derivative g2 (at (2*x - 1))) has_integral i2) {1/2..1}"
using has_integral_affinity01 [OF 1, where m= 2 and c=0, THEN has_integral_cmul [where c=2]]
has_integral_affinity01 [OF 2, where m= 2 and c="-1", THEN has_integral_cmul [where c=2]]
by (simp_all only: image_affinity_atLeastAtMost_div_diff, simp_all add: scaleR_conv_of_real mult_ac)
have g1: "\<lbrakk>0 \<le> z; z*2 < 1; z*2 \<notin> s1\<rbrakk> \<Longrightarrow>
vector_derivative (\<lambda>x. if x*2 \<le> 1 then g1 (2*x) else g2 (2*x - 1)) (at z) =
2 *\<^sub>R vector_derivative g1 (at (z*2))" for z
apply (rule vector_derivative_at [OF has_vector_derivative_transform_within [where f = "(\<lambda>x. g1(2*x))" and d = "\<bar>z - 1/2\<bar>"]])
apply (simp_all add: dist_real_def abs_if split: if_split_asm)
apply (rule vector_diff_chain_at [of "\<lambda>x. 2*x" 2 _ g1, simplified o_def])
apply (simp add: has_vector_derivative_def has_derivative_def bounded_linear_mult_left)
using s1
apply (auto simp: algebra_simps vector_derivative_works)
done
have g2: "\<lbrakk>1 < z*2; z \<le> 1; z*2 - 1 \<notin> s2\<rbrakk> \<Longrightarrow>
vector_derivative (\<lambda>x. if x*2 \<le> 1 then g1 (2*x) else g2 (2*x - 1)) (at z) =
2 *\<^sub>R vector_derivative g2 (at (z*2 - 1))" for z
apply (rule vector_derivative_at [OF has_vector_derivative_transform_within [where f = "(\<lambda>x. g2 (2*x - 1))" and d = "\<bar>z - 1/2\<bar>"]])
apply (simp_all add: dist_real_def abs_if split: if_split_asm)
apply (rule vector_diff_chain_at [of "\<lambda>x. 2*x - 1" 2 _ g2, simplified o_def])
apply (simp add: has_vector_derivative_def has_derivative_def bounded_linear_mult_left)
using s2
apply (auto simp: algebra_simps vector_derivative_works)
done
have "((\<lambda>x. f ((g1 +++ g2) x) * vector_derivative (g1 +++ g2) (at x)) has_integral i1) {0..1/2}"
apply (rule has_integral_spike_finite [OF _ _ i1, of "insert (1/2) ((*)2 -` s1)"])
using s1
apply (force intro: finite_vimageI [where h = "(*)2"] inj_onI)
apply (clarsimp simp add: joinpaths_def scaleR_conv_of_real mult_ac g1)
done
moreover have "((\<lambda>x. f ((g1 +++ g2) x) * vector_derivative (g1 +++ g2) (at x)) has_integral i2) {1/2..1}"
apply (rule has_integral_spike_finite [OF _ _ i2, of "insert (1/2) ((\<lambda>x. 2*x-1) -` s2)"])
using s2
apply (force intro: finite_vimageI [where h = "\<lambda>x. 2*x-1"] inj_onI)
apply (clarsimp simp add: joinpaths_def scaleR_conv_of_real mult_ac g2)
done
ultimately
show ?thesis
apply (simp add: has_contour_integral)
apply (rule has_integral_combine [where c = "1/2"], auto)
done
qed
lemma contour_integrable_joinI:
assumes "f contour_integrable_on g1" "f contour_integrable_on g2"
"valid_path g1" "valid_path g2"
shows "f contour_integrable_on (g1 +++ g2)"
using assms
by (meson has_contour_integral_join contour_integrable_on_def)
lemma contour_integrable_joinD1:
assumes "f contour_integrable_on (g1 +++ g2)" "valid_path g1"
shows "f contour_integrable_on g1"
proof -
obtain s1
where s1: "finite s1" "\<forall>x\<in>{0..1} - s1. g1 differentiable at x"
using assms by (auto simp: valid_path_def piecewise_C1_differentiable_on_def C1_differentiable_on_eq)
have "(\<lambda>x. f ((g1 +++ g2) (x/2)) * vector_derivative (g1 +++ g2) (at (x/2))) integrable_on {0..1}"
using assms
apply (auto simp: contour_integrable_on)
apply (drule integrable_on_subcbox [where a=0 and b="1/2"])
apply (auto intro: integrable_affinity [of _ 0 "1/2::real" "1/2" 0, simplified])
done
then have *: "(\<lambda>x. (f ((g1 +++ g2) (x/2))/2) * vector_derivative (g1 +++ g2) (at (x/2))) integrable_on {0..1}"
by (auto dest: integrable_cmul [where c="1/2"] simp: scaleR_conv_of_real)
have g1: "\<lbrakk>0 < z; z < 1; z \<notin> s1\<rbrakk> \<Longrightarrow>
vector_derivative (\<lambda>x. if x*2 \<le> 1 then g1 (2*x) else g2 (2*x - 1)) (at (z/2)) =
2 *\<^sub>R vector_derivative g1 (at z)" for z
apply (rule vector_derivative_at [OF has_vector_derivative_transform_within [where f = "(\<lambda>x. g1(2*x))" and d = "\<bar>(z-1)/2\<bar>"]])
apply (simp_all add: field_simps dist_real_def abs_if split: if_split_asm)
apply (rule vector_diff_chain_at [of "\<lambda>x. x*2" 2 _ g1, simplified o_def])
using s1
apply (auto simp: vector_derivative_works has_vector_derivative_def has_derivative_def bounded_linear_mult_left)
done
show ?thesis
using s1
apply (auto simp: contour_integrable_on)
apply (rule integrable_spike_finite [of "{0,1} \<union> s1", OF _ _ *])
apply (auto simp: joinpaths_def scaleR_conv_of_real g1)
done
qed
lemma contour_integrable_joinD2:
assumes "f contour_integrable_on (g1 +++ g2)" "valid_path g2"
shows "f contour_integrable_on g2"
proof -
obtain s2
where s2: "finite s2" "\<forall>x\<in>{0..1} - s2. g2 differentiable at x"
using assms by (auto simp: valid_path_def piecewise_C1_differentiable_on_def C1_differentiable_on_eq)
have "(\<lambda>x. f ((g1 +++ g2) (x/2 + 1/2)) * vector_derivative (g1 +++ g2) (at (x/2 + 1/2))) integrable_on {0..1}"
using assms
apply (auto simp: contour_integrable_on)
apply (drule integrable_on_subcbox [where a="1/2" and b=1], auto)
apply (drule integrable_affinity [of _ "1/2::real" 1 "1/2" "1/2", simplified])
apply (simp add: image_affinity_atLeastAtMost_diff)
done
then have *: "(\<lambda>x. (f ((g1 +++ g2) (x/2 + 1/2))/2) * vector_derivative (g1 +++ g2) (at (x/2 + 1/2)))
integrable_on {0..1}"
by (auto dest: integrable_cmul [where c="1/2"] simp: scaleR_conv_of_real)
have g2: "\<lbrakk>0 < z; z < 1; z \<notin> s2\<rbrakk> \<Longrightarrow>
vector_derivative (\<lambda>x. if x*2 \<le> 1 then g1 (2*x) else g2 (2*x - 1)) (at (z/2+1/2)) =
2 *\<^sub>R vector_derivative g2 (at z)" for z
apply (rule vector_derivative_at [OF has_vector_derivative_transform_within [where f = "(\<lambda>x. g2(2*x-1))" and d = "\<bar>z/2\<bar>"]])
apply (simp_all add: field_simps dist_real_def abs_if split: if_split_asm)
apply (rule vector_diff_chain_at [of "\<lambda>x. x*2-1" 2 _ g2, simplified o_def])
using s2
apply (auto simp: has_vector_derivative_def has_derivative_def bounded_linear_mult_left
vector_derivative_works add_divide_distrib)
done
show ?thesis
using s2
apply (auto simp: contour_integrable_on)
apply (rule integrable_spike_finite [of "{0,1} \<union> s2", OF _ _ *])
apply (auto simp: joinpaths_def scaleR_conv_of_real g2)
done
qed
lemma contour_integrable_join [simp]:
shows
"\<lbrakk>valid_path g1; valid_path g2\<rbrakk>
\<Longrightarrow> f contour_integrable_on (g1 +++ g2) \<longleftrightarrow> f contour_integrable_on g1 \<and> f contour_integrable_on g2"
using contour_integrable_joinD1 contour_integrable_joinD2 contour_integrable_joinI by blast
lemma contour_integral_join [simp]:
shows
"\<lbrakk>f contour_integrable_on g1; f contour_integrable_on g2; valid_path g1; valid_path g2\<rbrakk>
\<Longrightarrow> contour_integral (g1 +++ g2) f = contour_integral g1 f + contour_integral g2 f"
by (simp add: has_contour_integral_integral has_contour_integral_join contour_integral_unique)
subsection\<^marker>\<open>tag unimportant\<close> \<open>Shifting the starting point of a (closed) path\<close>
lemma has_contour_integral_shiftpath:
assumes f: "(f has_contour_integral i) g" "valid_path g"
and a: "a \<in> {0..1}"
shows "(f has_contour_integral i) (shiftpath a g)"
proof -
obtain s
where s: "finite s" and g: "\<forall>x\<in>{0..1} - s. g differentiable at x"
using assms by (auto simp: valid_path_def piecewise_C1_differentiable_on_def C1_differentiable_on_eq)
have *: "((\<lambda>x. f (g x) * vector_derivative g (at x)) has_integral i) {0..1}"
using assms by (auto simp: has_contour_integral)
then have i: "i = integral {a..1} (\<lambda>x. f (g x) * vector_derivative g (at x)) +
integral {0..a} (\<lambda>x. f (g x) * vector_derivative g (at x))"
apply (rule has_integral_unique)
apply (subst add.commute)
apply (subst Henstock_Kurzweil_Integration.integral_combine)
using assms * integral_unique by auto
{ fix x
have "0 \<le> x \<Longrightarrow> x + a < 1 \<Longrightarrow> x \<notin> (\<lambda>x. x - a) ` s \<Longrightarrow>
vector_derivative (shiftpath a g) (at x) = vector_derivative g (at (x + a))"
unfolding shiftpath_def
apply (rule vector_derivative_at [OF has_vector_derivative_transform_within [where f = "(\<lambda>x. g(a+x))" and d = "dist(1-a) x"]])
apply (auto simp: field_simps dist_real_def abs_if split: if_split_asm)
apply (rule vector_diff_chain_at [of "\<lambda>x. x+a" 1 _ g, simplified o_def scaleR_one])
apply (intro derivative_eq_intros | simp)+
using g
apply (drule_tac x="x+a" in bspec)
using a apply (auto simp: has_vector_derivative_def vector_derivative_works image_def add.commute)
done
} note vd1 = this
{ fix x
have "1 < x + a \<Longrightarrow> x \<le> 1 \<Longrightarrow> x \<notin> (\<lambda>x. x - a + 1) ` s \<Longrightarrow>
vector_derivative (shiftpath a g) (at x) = vector_derivative g (at (x + a - 1))"
unfolding shiftpath_def
apply (rule vector_derivative_at [OF has_vector_derivative_transform_within [where f = "(\<lambda>x. g(a+x-1))" and d = "dist (1-a) x"]])
apply (auto simp: field_simps dist_real_def abs_if split: if_split_asm)
apply (rule vector_diff_chain_at [of "\<lambda>x. x+a-1" 1 _ g, simplified o_def scaleR_one])
apply (intro derivative_eq_intros | simp)+
using g
apply (drule_tac x="x+a-1" in bspec)
using a apply (auto simp: has_vector_derivative_def vector_derivative_works image_def add.commute)
done
} note vd2 = this
have va1: "(\<lambda>x. f (g x) * vector_derivative g (at x)) integrable_on ({a..1})"
using * a by (fastforce intro: integrable_subinterval_real)
have v0a: "(\<lambda>x. f (g x) * vector_derivative g (at x)) integrable_on ({0..a})"
apply (rule integrable_subinterval_real)
using * a by auto
have "((\<lambda>x. f (shiftpath a g x) * vector_derivative (shiftpath a g) (at x))
has_integral integral {a..1} (\<lambda>x. f (g x) * vector_derivative g (at x))) {0..1 - a}"
apply (rule has_integral_spike_finite
[where S = "{1-a} \<union> (\<lambda>x. x-a) ` s" and f = "\<lambda>x. f(g(a+x)) * vector_derivative g (at(a+x))"])
using s apply blast
using a apply (auto simp: algebra_simps vd1)
apply (force simp: shiftpath_def add.commute)
using has_integral_affinity [where m=1 and c=a, simplified, OF integrable_integral [OF va1]]
apply (simp add: image_affinity_atLeastAtMost_diff [where m=1 and c=a, simplified] add.commute)
done
moreover
have "((\<lambda>x. f (shiftpath a g x) * vector_derivative (shiftpath a g) (at x))
has_integral integral {0..a} (\<lambda>x. f (g x) * vector_derivative g (at x))) {1 - a..1}"
apply (rule has_integral_spike_finite
[where S = "{1-a} \<union> (\<lambda>x. x-a+1) ` s" and f = "\<lambda>x. f(g(a+x-1)) * vector_derivative g (at(a+x-1))"])
using s apply blast
using a apply (auto simp: algebra_simps vd2)
apply (force simp: shiftpath_def add.commute)
using has_integral_affinity [where m=1 and c="a-1", simplified, OF integrable_integral [OF v0a]]
apply (simp add: image_affinity_atLeastAtMost [where m=1 and c="1-a", simplified])
apply (simp add: algebra_simps)
done
ultimately show ?thesis
using a
by (auto simp: i has_contour_integral intro: has_integral_combine [where c = "1-a"])
qed
lemma has_contour_integral_shiftpath_D:
assumes "(f has_contour_integral i) (shiftpath a g)"
"valid_path g" "pathfinish g = pathstart g" "a \<in> {0..1}"
shows "(f has_contour_integral i) g"
proof -
obtain s
where s: "finite s" and g: "\<forall>x\<in>{0..1} - s. g differentiable at x"
using assms by (auto simp: valid_path_def piecewise_C1_differentiable_on_def C1_differentiable_on_eq)
{ fix x
assume x: "0 < x" "x < 1" "x \<notin> s"
then have gx: "g differentiable at x"
using g by auto
have "vector_derivative g (at x within {0..1}) =
vector_derivative (shiftpath (1 - a) (shiftpath a g)) (at x within {0..1})"
apply (rule vector_derivative_at_within_ivl
[OF has_vector_derivative_transform_within_open
[where f = "(shiftpath (1 - a) (shiftpath a g))" and S = "{0<..<1}-s"]])
using s g assms x
apply (auto simp: finite_imp_closed open_Diff shiftpath_shiftpath
at_within_interior [of _ "{0..1}"] vector_derivative_works [symmetric])
apply (rule differentiable_transform_within [OF gx, of "min x (1-x)"])
apply (auto simp: dist_real_def shiftpath_shiftpath abs_if split: if_split_asm)
done
} note vd = this
have fi: "(f has_contour_integral i) (shiftpath (1 - a) (shiftpath a g))"
using assms by (auto intro!: has_contour_integral_shiftpath)
show ?thesis
apply (simp add: has_contour_integral_def)
apply (rule has_integral_spike_finite [of "{0,1} \<union> s", OF _ _ fi [unfolded has_contour_integral_def]])
using s assms vd
apply (auto simp: Path_Connected.shiftpath_shiftpath)
done
qed
lemma has_contour_integral_shiftpath_eq:
assumes "valid_path g" "pathfinish g = pathstart g" "a \<in> {0..1}"
shows "(f has_contour_integral i) (shiftpath a g) \<longleftrightarrow> (f has_contour_integral i) g"
using assms has_contour_integral_shiftpath has_contour_integral_shiftpath_D by blast
lemma contour_integrable_on_shiftpath_eq:
assumes "valid_path g" "pathfinish g = pathstart g" "a \<in> {0..1}"
shows "f contour_integrable_on (shiftpath a g) \<longleftrightarrow> f contour_integrable_on g"
using assms contour_integrable_on_def has_contour_integral_shiftpath_eq by auto
lemma contour_integral_shiftpath:
assumes "valid_path g" "pathfinish g = pathstart g" "a \<in> {0..1}"
shows "contour_integral (shiftpath a g) f = contour_integral g f"
using assms
by (simp add: contour_integral_def contour_integrable_on_def has_contour_integral_shiftpath_eq)
subsection\<^marker>\<open>tag unimportant\<close> \<open>More about straight-line paths\<close>
lemma has_contour_integral_linepath:
shows "(f has_contour_integral i) (linepath a b) \<longleftrightarrow>
((\<lambda>x. f(linepath a b x) * (b - a)) has_integral i) {0..1}"
by (simp add: has_contour_integral)
lemma has_contour_integral_trivial [iff]: "(f has_contour_integral 0) (linepath a a)"
by (simp add: has_contour_integral_linepath)
lemma has_contour_integral_trivial_iff [simp]: "(f has_contour_integral i) (linepath a a) \<longleftrightarrow> i=0"
using has_contour_integral_unique by blast
lemma contour_integral_trivial [simp]: "contour_integral (linepath a a) f = 0"
using has_contour_integral_trivial contour_integral_unique by blast
subsection\<open>Relation to subpath construction\<close>
lemma has_contour_integral_subpath_refl [iff]: "(f has_contour_integral 0) (subpath u u g)"
by (simp add: has_contour_integral subpath_def)
lemma contour_integrable_subpath_refl [iff]: "f contour_integrable_on (subpath u u g)"
using has_contour_integral_subpath_refl contour_integrable_on_def by blast
lemma contour_integral_subpath_refl [simp]: "contour_integral (subpath u u g) f = 0"
by (simp add: contour_integral_unique)
lemma has_contour_integral_subpath:
assumes f: "f contour_integrable_on g" and g: "valid_path g"
and uv: "u \<in> {0..1}" "v \<in> {0..1}" "u \<le> v"
shows "(f has_contour_integral integral {u..v} (\<lambda>x. f(g x) * vector_derivative g (at x)))
(subpath u v g)"
proof (cases "v=u")
case True
then show ?thesis
using f by (simp add: contour_integrable_on_def subpath_def has_contour_integral)
next
case False
obtain s where s: "\<And>x. x \<in> {0..1} - s \<Longrightarrow> g differentiable at x" and fs: "finite s"
using g unfolding piecewise_C1_differentiable_on_def C1_differentiable_on_eq valid_path_def by blast
have *: "((\<lambda>x. f (g ((v - u) * x + u)) * vector_derivative g (at ((v - u) * x + u)))
has_integral (1 / (v - u)) * integral {u..v} (\<lambda>t. f (g t) * vector_derivative g (at t)))
{0..1}"
using f uv
apply (simp add: contour_integrable_on subpath_def has_contour_integral)
apply (drule integrable_on_subcbox [where a=u and b=v, simplified])
apply (simp_all add: has_integral_integral)
apply (drule has_integral_affinity [where m="v-u" and c=u, simplified])
apply (simp_all add: False image_affinity_atLeastAtMost_div_diff scaleR_conv_of_real)
apply (simp add: divide_simps False)
done
{ fix x
have "x \<in> {0..1} \<Longrightarrow>
x \<notin> (\<lambda>t. (v-u) *\<^sub>R t + u) -` s \<Longrightarrow>
vector_derivative (\<lambda>x. g ((v-u) * x + u)) (at x) = (v-u) *\<^sub>R vector_derivative g (at ((v-u) * x + u))"
apply (rule vector_derivative_at [OF vector_diff_chain_at [simplified o_def]])
apply (intro derivative_eq_intros | simp)+
apply (cut_tac s [of "(v - u) * x + u"])
using uv mult_left_le [of x "v-u"]
apply (auto simp: vector_derivative_works)
done
} note vd = this
show ?thesis
apply (cut_tac has_integral_cmul [OF *, where c = "v-u"])
using fs assms
apply (simp add: False subpath_def has_contour_integral)
apply (rule_tac S = "(\<lambda>t. ((v-u) *\<^sub>R t + u)) -` s" in has_integral_spike_finite)
apply (auto simp: inj_on_def False finite_vimageI vd scaleR_conv_of_real)
done
qed
lemma contour_integrable_subpath:
assumes "f contour_integrable_on g" "valid_path g" "u \<in> {0..1}" "v \<in> {0..1}"
shows "f contour_integrable_on (subpath u v g)"
apply (cases u v rule: linorder_class.le_cases)
apply (metis contour_integrable_on_def has_contour_integral_subpath [OF assms])
apply (subst reversepath_subpath [symmetric])
apply (rule contour_integrable_reversepath)
using assms apply (blast intro: valid_path_subpath)
apply (simp add: contour_integrable_on_def)
using assms apply (blast intro: has_contour_integral_subpath)
done
lemma has_integral_contour_integral_subpath:
assumes "f contour_integrable_on g" "valid_path g" "u \<in> {0..1}" "v \<in> {0..1}" "u \<le> v"
shows "(((\<lambda>x. f(g x) * vector_derivative g (at x)))
has_integral contour_integral (subpath u v g) f) {u..v}"
using assms
apply (auto simp: has_integral_integrable_integral)
apply (rule integrable_on_subcbox [where a=u and b=v and S = "{0..1}", simplified])
apply (auto simp: contour_integral_unique [OF has_contour_integral_subpath] contour_integrable_on)
done
lemma contour_integral_subcontour_integral:
assumes "f contour_integrable_on g" "valid_path g" "u \<in> {0..1}" "v \<in> {0..1}" "u \<le> v"
shows "contour_integral (subpath u v g) f =
integral {u..v} (\<lambda>x. f(g x) * vector_derivative g (at x))"
using assms has_contour_integral_subpath contour_integral_unique by blast
lemma contour_integral_subpath_combine_less:
assumes "f contour_integrable_on g" "valid_path g" "u \<in> {0..1}" "v \<in> {0..1}" "w \<in> {0..1}"
"u<v" "v<w"
shows "contour_integral (subpath u v g) f + contour_integral (subpath v w g) f =
contour_integral (subpath u w g) f"
using assms apply (auto simp: contour_integral_subcontour_integral)
apply (rule Henstock_Kurzweil_Integration.integral_combine, auto)
apply (rule integrable_on_subcbox [where a=u and b=w and S = "{0..1}", simplified])
apply (auto simp: contour_integrable_on)
done
lemma contour_integral_subpath_combine:
assumes "f contour_integrable_on g" "valid_path g" "u \<in> {0..1}" "v \<in> {0..1}" "w \<in> {0..1}"
shows "contour_integral (subpath u v g) f + contour_integral (subpath v w g) f =
contour_integral (subpath u w g) f"
proof (cases "u\<noteq>v \<and> v\<noteq>w \<and> u\<noteq>w")
case True
have *: "subpath v u g = reversepath(subpath u v g) \<and>
subpath w u g = reversepath(subpath u w g) \<and>
subpath w v g = reversepath(subpath v w g)"
by (auto simp: reversepath_subpath)
have "u < v \<and> v < w \<or>
u < w \<and> w < v \<or>
v < u \<and> u < w \<or>
v < w \<and> w < u \<or>
w < u \<and> u < v \<or>
w < v \<and> v < u"
using True assms by linarith
with assms show ?thesis
using contour_integral_subpath_combine_less [of f g u v w]
contour_integral_subpath_combine_less [of f g u w v]
contour_integral_subpath_combine_less [of f g v u w]
contour_integral_subpath_combine_less [of f g v w u]
contour_integral_subpath_combine_less [of f g w u v]
contour_integral_subpath_combine_less [of f g w v u]
apply simp
apply (elim disjE)
apply (auto simp: * contour_integral_reversepath contour_integrable_subpath
valid_path_subpath algebra_simps)
done
next
case False
then show ?thesis
apply (auto)
using assms
by (metis eq_neg_iff_add_eq_0 contour_integral_reversepath reversepath_subpath valid_path_subpath)
qed
lemma contour_integral_integral:
"contour_integral g f = integral {0..1} (\<lambda>x. f (g x) * vector_derivative g (at x))"
by (simp add: contour_integral_def integral_def has_contour_integral contour_integrable_on)
lemma contour_integral_cong:
assumes "g = g'" "\<And>x. x \<in> path_image g \<Longrightarrow> f x = f' x"
shows "contour_integral g f = contour_integral g' f'"
unfolding contour_integral_integral using assms
by (intro integral_cong) (auto simp: path_image_def)
text \<open>Contour integral along a segment on the real axis\<close>
lemma has_contour_integral_linepath_Reals_iff:
fixes a b :: complex and f :: "complex \<Rightarrow> complex"
assumes "a \<in> Reals" "b \<in> Reals" "Re a < Re b"
shows "(f has_contour_integral I) (linepath a b) \<longleftrightarrow>
((\<lambda>x. f (of_real x)) has_integral I) {Re a..Re b}"
proof -
from assms have [simp]: "of_real (Re a) = a" "of_real (Re b) = b"
by (simp_all add: complex_eq_iff)
from assms have "a \<noteq> b" by auto
have "((\<lambda>x. f (of_real x)) has_integral I) (cbox (Re a) (Re b)) \<longleftrightarrow>
((\<lambda>x. f (a + b * of_real x - a * of_real x)) has_integral I /\<^sub>R (Re b - Re a)) {0..1}"
by (subst has_integral_affinity_iff [of "Re b - Re a" _ "Re a", symmetric])
(insert assms, simp_all add: field_simps scaleR_conv_of_real)
also have "(\<lambda>x. f (a + b * of_real x - a * of_real x)) =
(\<lambda>x. (f (a + b * of_real x - a * of_real x) * (b - a)) /\<^sub>R (Re b - Re a))"
using \<open>a \<noteq> b\<close> by (auto simp: field_simps fun_eq_iff scaleR_conv_of_real)
also have "(\<dots> has_integral I /\<^sub>R (Re b - Re a)) {0..1} \<longleftrightarrow>
((\<lambda>x. f (linepath a b x) * (b - a)) has_integral I) {0..1}" using assms
by (subst has_integral_cmul_iff) (auto simp: linepath_def scaleR_conv_of_real algebra_simps)
also have "\<dots> \<longleftrightarrow> (f has_contour_integral I) (linepath a b)" unfolding has_contour_integral_def
by (intro has_integral_cong) (simp add: vector_derivative_linepath_within)
finally show ?thesis by simp
qed
lemma contour_integrable_linepath_Reals_iff:
fixes a b :: complex and f :: "complex \<Rightarrow> complex"
assumes "a \<in> Reals" "b \<in> Reals" "Re a < Re b"
shows "(f contour_integrable_on linepath a b) \<longleftrightarrow>
(\<lambda>x. f (of_real x)) integrable_on {Re a..Re b}"
using has_contour_integral_linepath_Reals_iff[OF assms, of f]
by (auto simp: contour_integrable_on_def integrable_on_def)
lemma contour_integral_linepath_Reals_eq:
fixes a b :: complex and f :: "complex \<Rightarrow> complex"
assumes "a \<in> Reals" "b \<in> Reals" "Re a < Re b"
shows "contour_integral (linepath a b) f = integral {Re a..Re b} (\<lambda>x. f (of_real x))"
proof (cases "f contour_integrable_on linepath a b")
case True
thus ?thesis using has_contour_integral_linepath_Reals_iff[OF assms, of f]
using has_contour_integral_integral has_contour_integral_unique by blast
next
case False
thus ?thesis using contour_integrable_linepath_Reals_iff[OF assms, of f]
by (simp add: not_integrable_contour_integral not_integrable_integral)
qed
text \<open>Cauchy's theorem where there's a primitive\<close>
lemma contour_integral_primitive_lemma:
fixes f :: "complex \<Rightarrow> complex" and g :: "real \<Rightarrow> complex"
assumes "a \<le> b"
and "\<And>x. x \<in> s \<Longrightarrow> (f has_field_derivative f' x) (at x within s)"
and "g piecewise_differentiable_on {a..b}" "\<And>x. x \<in> {a..b} \<Longrightarrow> g x \<in> s"
shows "((\<lambda>x. f'(g x) * vector_derivative g (at x within {a..b}))
has_integral (f(g b) - f(g a))) {a..b}"
proof -
obtain k where k: "finite k" "\<forall>x\<in>{a..b} - k. g differentiable (at x within {a..b})" and cg: "continuous_on {a..b} g"
using assms by (auto simp: piecewise_differentiable_on_def)
have cfg: "continuous_on {a..b} (\<lambda>x. f (g x))"
apply (rule continuous_on_compose [OF cg, unfolded o_def])
using assms
apply (metis field_differentiable_def field_differentiable_imp_continuous_at continuous_on_eq_continuous_within continuous_on_subset image_subset_iff)
done
{ fix x::real
assume a: "a < x" and b: "x < b" and xk: "x \<notin> k"
then have "g differentiable at x within {a..b}"
using k by (simp add: differentiable_at_withinI)
then have "(g has_vector_derivative vector_derivative g (at x within {a..b})) (at x within {a..b})"
by (simp add: vector_derivative_works has_field_derivative_def scaleR_conv_of_real)
then have gdiff: "(g has_derivative (\<lambda>u. u * vector_derivative g (at x within {a..b}))) (at x within {a..b})"
by (simp add: has_vector_derivative_def scaleR_conv_of_real)
have "(f has_field_derivative (f' (g x))) (at (g x) within g ` {a..b})"
using assms by (metis a atLeastAtMost_iff b DERIV_subset image_subset_iff less_eq_real_def)
then have fdiff: "(f has_derivative (*) (f' (g x))) (at (g x) within g ` {a..b})"
by (simp add: has_field_derivative_def)
have "((\<lambda>x. f (g x)) has_vector_derivative f' (g x) * vector_derivative g (at x within {a..b})) (at x within {a..b})"
using diff_chain_within [OF gdiff fdiff]
by (simp add: has_vector_derivative_def scaleR_conv_of_real o_def mult_ac)
} note * = this
show ?thesis
apply (rule fundamental_theorem_of_calculus_interior_strong)
using k assms cfg *
apply (auto simp: at_within_Icc_at)
done
qed
lemma contour_integral_primitive:
assumes "\<And>x. x \<in> s \<Longrightarrow> (f has_field_derivative f' x) (at x within s)"
and "valid_path g" "path_image g \<subseteq> s"
shows "(f' has_contour_integral (f(pathfinish g) - f(pathstart g))) g"
using assms
apply (simp add: valid_path_def path_image_def pathfinish_def pathstart_def has_contour_integral_def)
apply (auto intro!: piecewise_C1_imp_differentiable contour_integral_primitive_lemma [of 0 1 s])
done
corollary Cauchy_theorem_primitive:
assumes "\<And>x. x \<in> s \<Longrightarrow> (f has_field_derivative f' x) (at x within s)"
and "valid_path g" "path_image g \<subseteq> s" "pathfinish g = pathstart g"
shows "(f' has_contour_integral 0) g"
using assms
by (metis diff_self contour_integral_primitive)
text\<open>Existence of path integral for continuous function\<close>
lemma contour_integrable_continuous_linepath:
assumes "continuous_on (closed_segment a b) f"
shows "f contour_integrable_on (linepath a b)"
proof -
have "continuous_on {0..1} ((\<lambda>x. f x * (b - a)) \<circ> linepath a b)"
apply (rule continuous_on_compose [OF continuous_on_linepath], simp add: linepath_image_01)
apply (rule continuous_intros | simp add: assms)+
done
then show ?thesis
apply (simp add: contour_integrable_on_def has_contour_integral_def integrable_on_def [symmetric])
apply (rule integrable_continuous [of 0 "1::real", simplified])
apply (rule continuous_on_eq [where f = "\<lambda>x. f(linepath a b x)*(b - a)"])
apply (auto simp: vector_derivative_linepath_within)
done
qed
lemma has_field_der_id: "((\<lambda>x. x\<^sup>2 / 2) has_field_derivative x) (at x)"
by (rule has_derivative_imp_has_field_derivative)
(rule derivative_intros | simp)+
lemma contour_integral_id [simp]: "contour_integral (linepath a b) (\<lambda>y. y) = (b^2 - a^2)/2"
apply (rule contour_integral_unique)
using contour_integral_primitive [of UNIV "\<lambda>x. x^2/2" "\<lambda>x. x" "linepath a b"]
apply (auto simp: field_simps has_field_der_id)
done
lemma contour_integrable_on_const [iff]: "(\<lambda>x. c) contour_integrable_on (linepath a b)"
by (simp add: contour_integrable_continuous_linepath)
lemma contour_integrable_on_id [iff]: "(\<lambda>x. x) contour_integrable_on (linepath a b)"
by (simp add: contour_integrable_continuous_linepath)
subsection\<^marker>\<open>tag unimportant\<close> \<open>Arithmetical combining theorems\<close>
lemma has_contour_integral_neg:
"(f has_contour_integral i) g \<Longrightarrow> ((\<lambda>x. -(f x)) has_contour_integral (-i)) g"
by (simp add: has_integral_neg has_contour_integral_def)
lemma has_contour_integral_add:
"\<lbrakk>(f1 has_contour_integral i1) g; (f2 has_contour_integral i2) g\<rbrakk>
\<Longrightarrow> ((\<lambda>x. f1 x + f2 x) has_contour_integral (i1 + i2)) g"
by (simp add: has_integral_add has_contour_integral_def algebra_simps)
lemma has_contour_integral_diff:
"\<lbrakk>(f1 has_contour_integral i1) g; (f2 has_contour_integral i2) g\<rbrakk>
\<Longrightarrow> ((\<lambda>x. f1 x - f2 x) has_contour_integral (i1 - i2)) g"
by (simp add: has_integral_diff has_contour_integral_def algebra_simps)
lemma has_contour_integral_lmul:
"(f has_contour_integral i) g \<Longrightarrow> ((\<lambda>x. c * (f x)) has_contour_integral (c*i)) g"
apply (simp add: has_contour_integral_def)
apply (drule has_integral_mult_right)
apply (simp add: algebra_simps)
done
lemma has_contour_integral_rmul:
"(f has_contour_integral i) g \<Longrightarrow> ((\<lambda>x. (f x) * c) has_contour_integral (i*c)) g"
apply (drule has_contour_integral_lmul)
apply (simp add: mult.commute)
done
lemma has_contour_integral_div:
"(f has_contour_integral i) g \<Longrightarrow> ((\<lambda>x. f x/c) has_contour_integral (i/c)) g"
by (simp add: field_class.field_divide_inverse) (metis has_contour_integral_rmul)
lemma has_contour_integral_eq:
"\<lbrakk>(f has_contour_integral y) p; \<And>x. x \<in> path_image p \<Longrightarrow> f x = g x\<rbrakk> \<Longrightarrow> (g has_contour_integral y) p"
apply (simp add: path_image_def has_contour_integral_def)
by (metis (no_types, lifting) image_eqI has_integral_eq)
lemma has_contour_integral_bound_linepath:
assumes "(f has_contour_integral i) (linepath a b)"
"0 \<le> B" "\<And>x. x \<in> closed_segment a b \<Longrightarrow> norm(f x) \<le> B"
shows "norm i \<le> B * norm(b - a)"
proof -
{ fix x::real
assume x: "0 \<le> x" "x \<le> 1"
have "norm (f (linepath a b x)) *
norm (vector_derivative (linepath a b) (at x within {0..1})) \<le> B * norm (b - a)"
by (auto intro: mult_mono simp: assms linepath_in_path of_real_linepath vector_derivative_linepath_within x)
} note * = this
have "norm i \<le> (B * norm (b - a)) * content (cbox 0 (1::real))"
apply (rule has_integral_bound
[of _ "\<lambda>x. f (linepath a b x) * vector_derivative (linepath a b) (at x within {0..1})"])
using assms * unfolding has_contour_integral_def
apply (auto simp: norm_mult)
done
then show ?thesis
by (auto simp: content_real)
qed
(*UNUSED
lemma has_contour_integral_bound_linepath_strong:
fixes a :: real and f :: "complex \<Rightarrow> real"
assumes "(f has_contour_integral i) (linepath a b)"
"finite k"
"0 \<le> B" "\<And>x::real. x \<in> closed_segment a b - k \<Longrightarrow> norm(f x) \<le> B"
shows "norm i \<le> B*norm(b - a)"
*)
lemma has_contour_integral_const_linepath: "((\<lambda>x. c) has_contour_integral c*(b - a))(linepath a b)"
unfolding has_contour_integral_linepath
by (metis content_real diff_0_right has_integral_const_real lambda_one of_real_1 scaleR_conv_of_real zero_le_one)
lemma has_contour_integral_0: "((\<lambda>x. 0) has_contour_integral 0) g"
by (simp add: has_contour_integral_def)
lemma has_contour_integral_is_0:
"(\<And>z. z \<in> path_image g \<Longrightarrow> f z = 0) \<Longrightarrow> (f has_contour_integral 0) g"
by (rule has_contour_integral_eq [OF has_contour_integral_0]) auto
lemma has_contour_integral_sum:
"\<lbrakk>finite s; \<And>a. a \<in> s \<Longrightarrow> (f a has_contour_integral i a) p\<rbrakk>
\<Longrightarrow> ((\<lambda>x. sum (\<lambda>a. f a x) s) has_contour_integral sum i s) p"
by (induction s rule: finite_induct) (auto simp: has_contour_integral_0 has_contour_integral_add)
subsection\<^marker>\<open>tag unimportant\<close> \<open>Operations on path integrals\<close>
lemma contour_integral_const_linepath [simp]: "contour_integral (linepath a b) (\<lambda>x. c) = c*(b - a)"
by (rule contour_integral_unique [OF has_contour_integral_const_linepath])
lemma contour_integral_neg:
"f contour_integrable_on g \<Longrightarrow> contour_integral g (\<lambda>x. -(f x)) = -(contour_integral g f)"
by (simp add: contour_integral_unique has_contour_integral_integral has_contour_integral_neg)
lemma contour_integral_add:
"f1 contour_integrable_on g \<Longrightarrow> f2 contour_integrable_on g \<Longrightarrow> contour_integral g (\<lambda>x. f1 x + f2 x) =
contour_integral g f1 + contour_integral g f2"
by (simp add: contour_integral_unique has_contour_integral_integral has_contour_integral_add)
lemma contour_integral_diff:
"f1 contour_integrable_on g \<Longrightarrow> f2 contour_integrable_on g \<Longrightarrow> contour_integral g (\<lambda>x. f1 x - f2 x) =
contour_integral g f1 - contour_integral g f2"
by (simp add: contour_integral_unique has_contour_integral_integral has_contour_integral_diff)
lemma contour_integral_lmul:
shows "f contour_integrable_on g
\<Longrightarrow> contour_integral g (\<lambda>x. c * f x) = c*contour_integral g f"
by (simp add: contour_integral_unique has_contour_integral_integral has_contour_integral_lmul)
lemma contour_integral_rmul:
shows "f contour_integrable_on g
\<Longrightarrow> contour_integral g (\<lambda>x. f x * c) = contour_integral g f * c"
by (simp add: contour_integral_unique has_contour_integral_integral has_contour_integral_rmul)
lemma contour_integral_div:
shows "f contour_integrable_on g
\<Longrightarrow> contour_integral g (\<lambda>x. f x / c) = contour_integral g f / c"
by (simp add: contour_integral_unique has_contour_integral_integral has_contour_integral_div)
lemma contour_integral_eq:
"(\<And>x. x \<in> path_image p \<Longrightarrow> f x = g x) \<Longrightarrow> contour_integral p f = contour_integral p g"
apply (simp add: contour_integral_def)
using has_contour_integral_eq
by (metis contour_integral_unique has_contour_integral_integrable has_contour_integral_integral)
lemma contour_integral_eq_0:
"(\<And>z. z \<in> path_image g \<Longrightarrow> f z = 0) \<Longrightarrow> contour_integral g f = 0"
by (simp add: has_contour_integral_is_0 contour_integral_unique)
lemma contour_integral_bound_linepath:
shows
"\<lbrakk>f contour_integrable_on (linepath a b);
0 \<le> B; \<And>x. x \<in> closed_segment a b \<Longrightarrow> norm(f x) \<le> B\<rbrakk>
\<Longrightarrow> norm(contour_integral (linepath a b) f) \<le> B*norm(b - a)"
apply (rule has_contour_integral_bound_linepath [of f])
apply (auto simp: has_contour_integral_integral)
done
lemma contour_integral_0 [simp]: "contour_integral g (\<lambda>x. 0) = 0"
by (simp add: contour_integral_unique has_contour_integral_0)
lemma contour_integral_sum:
"\<lbrakk>finite s; \<And>a. a \<in> s \<Longrightarrow> (f a) contour_integrable_on p\<rbrakk>
\<Longrightarrow> contour_integral p (\<lambda>x. sum (\<lambda>a. f a x) s) = sum (\<lambda>a. contour_integral p (f a)) s"
by (auto simp: contour_integral_unique has_contour_integral_sum has_contour_integral_integral)
lemma contour_integrable_eq:
"\<lbrakk>f contour_integrable_on p; \<And>x. x \<in> path_image p \<Longrightarrow> f x = g x\<rbrakk> \<Longrightarrow> g contour_integrable_on p"
unfolding contour_integrable_on_def
by (metis has_contour_integral_eq)
subsection\<^marker>\<open>tag unimportant\<close> \<open>Arithmetic theorems for path integrability\<close>
lemma contour_integrable_neg:
"f contour_integrable_on g \<Longrightarrow> (\<lambda>x. -(f x)) contour_integrable_on g"
using has_contour_integral_neg contour_integrable_on_def by blast
lemma contour_integrable_add:
"\<lbrakk>f1 contour_integrable_on g; f2 contour_integrable_on g\<rbrakk> \<Longrightarrow> (\<lambda>x. f1 x + f2 x) contour_integrable_on g"
using has_contour_integral_add contour_integrable_on_def
by fastforce
lemma contour_integrable_diff:
"\<lbrakk>f1 contour_integrable_on g; f2 contour_integrable_on g\<rbrakk> \<Longrightarrow> (\<lambda>x. f1 x - f2 x) contour_integrable_on g"
using has_contour_integral_diff contour_integrable_on_def
by fastforce
lemma contour_integrable_lmul:
"f contour_integrable_on g \<Longrightarrow> (\<lambda>x. c * f x) contour_integrable_on g"
using has_contour_integral_lmul contour_integrable_on_def
by fastforce
lemma contour_integrable_rmul:
"f contour_integrable_on g \<Longrightarrow> (\<lambda>x. f x * c) contour_integrable_on g"
using has_contour_integral_rmul contour_integrable_on_def
by fastforce
lemma contour_integrable_div:
"f contour_integrable_on g \<Longrightarrow> (\<lambda>x. f x / c) contour_integrable_on g"
using has_contour_integral_div contour_integrable_on_def
by fastforce
lemma contour_integrable_sum:
"\<lbrakk>finite s; \<And>a. a \<in> s \<Longrightarrow> (f a) contour_integrable_on p\<rbrakk>
\<Longrightarrow> (\<lambda>x. sum (\<lambda>a. f a x) s) contour_integrable_on p"
unfolding contour_integrable_on_def
by (metis has_contour_integral_sum)
subsection\<^marker>\<open>tag unimportant\<close> \<open>Reversing a path integral\<close>
lemma has_contour_integral_reverse_linepath:
"(f has_contour_integral i) (linepath a b)
\<Longrightarrow> (f has_contour_integral (-i)) (linepath b a)"
using has_contour_integral_reversepath valid_path_linepath by fastforce
lemma contour_integral_reverse_linepath:
"continuous_on (closed_segment a b) f
\<Longrightarrow> contour_integral (linepath a b) f = - (contour_integral(linepath b a) f)"
apply (rule contour_integral_unique)
apply (rule has_contour_integral_reverse_linepath)
by (simp add: closed_segment_commute contour_integrable_continuous_linepath has_contour_integral_integral)
(* Splitting a path integral in a flat way.*)
lemma has_contour_integral_split:
assumes f: "(f has_contour_integral i) (linepath a c)" "(f has_contour_integral j) (linepath c b)"
and k: "0 \<le> k" "k \<le> 1"
and c: "c - a = k *\<^sub>R (b - a)"
shows "(f has_contour_integral (i + j)) (linepath a b)"
proof (cases "k = 0 \<or> k = 1")
case True
then show ?thesis
using assms by auto
next
case False
then have k: "0 < k" "k < 1" "complex_of_real k \<noteq> 1"
using assms by auto
have c': "c = k *\<^sub>R (b - a) + a"
by (metis diff_add_cancel c)
have bc: "(b - c) = (1 - k) *\<^sub>R (b - a)"
by (simp add: algebra_simps c')
{ assume *: "((\<lambda>x. f ((1 - x) *\<^sub>R a + x *\<^sub>R c) * (c - a)) has_integral i) {0..1}"
have **: "\<And>x. ((k - x) / k) *\<^sub>R a + (x / k) *\<^sub>R c = (1 - x) *\<^sub>R a + x *\<^sub>R b"
using False apply (simp add: c' algebra_simps)
apply (simp add: real_vector.scale_left_distrib [symmetric] field_split_simps)
done
have "((\<lambda>x. f ((1 - x) *\<^sub>R a + x *\<^sub>R b) * (b - a)) has_integral i) {0..k}"
using k has_integral_affinity01 [OF *, of "inverse k" "0"]
apply (simp add: divide_simps mult.commute [of _ "k"] image_affinity_atLeastAtMost ** c)
apply (auto dest: has_integral_cmul [where c = "inverse k"])
done
} note fi = this
{ assume *: "((\<lambda>x. f ((1 - x) *\<^sub>R c + x *\<^sub>R b) * (b - c)) has_integral j) {0..1}"
have **: "\<And>x. (((1 - x) / (1 - k)) *\<^sub>R c + ((x - k) / (1 - k)) *\<^sub>R b) = ((1 - x) *\<^sub>R a + x *\<^sub>R b)"
using k
apply (simp add: c' field_simps)
apply (simp add: scaleR_conv_of_real divide_simps)
apply (simp add: field_simps)
done
have "((\<lambda>x. f ((1 - x) *\<^sub>R a + x *\<^sub>R b) * (b - a)) has_integral j) {k..1}"
using k has_integral_affinity01 [OF *, of "inverse(1 - k)" "-(k/(1 - k))"]
apply (simp add: divide_simps mult.commute [of _ "1-k"] image_affinity_atLeastAtMost ** bc)
apply (auto dest: has_integral_cmul [where k = "(1 - k) *\<^sub>R j" and c = "inverse (1 - k)"])
done
} note fj = this
show ?thesis
using f k
apply (simp add: has_contour_integral_linepath)
apply (simp add: linepath_def)
apply (rule has_integral_combine [OF _ _ fi fj], simp_all)
done
qed
lemma continuous_on_closed_segment_transform:
assumes f: "continuous_on (closed_segment a b) f"
and k: "0 \<le> k" "k \<le> 1"
and c: "c - a = k *\<^sub>R (b - a)"
shows "continuous_on (closed_segment a c) f"
proof -
have c': "c = (1 - k) *\<^sub>R a + k *\<^sub>R b"
using c by (simp add: algebra_simps)
have "closed_segment a c \<subseteq> closed_segment a b"
by (metis c' ends_in_segment(1) in_segment(1) k subset_closed_segment)
then show "continuous_on (closed_segment a c) f"
by (rule continuous_on_subset [OF f])
qed
lemma contour_integral_split:
assumes f: "continuous_on (closed_segment a b) f"
and k: "0 \<le> k" "k \<le> 1"
and c: "c - a = k *\<^sub>R (b - a)"
shows "contour_integral(linepath a b) f = contour_integral(linepath a c) f + contour_integral(linepath c b) f"
proof -
have c': "c = (1 - k) *\<^sub>R a + k *\<^sub>R b"
using c by (simp add: algebra_simps)
have "closed_segment a c \<subseteq> closed_segment a b"
by (metis c' ends_in_segment(1) in_segment(1) k subset_closed_segment)
moreover have "closed_segment c b \<subseteq> closed_segment a b"
by (metis c' ends_in_segment(2) in_segment(1) k subset_closed_segment)
ultimately
have *: "continuous_on (closed_segment a c) f" "continuous_on (closed_segment c b) f"
by (auto intro: continuous_on_subset [OF f])
show ?thesis
by (rule contour_integral_unique) (meson "*" c contour_integrable_continuous_linepath has_contour_integral_integral has_contour_integral_split k)
qed
lemma contour_integral_split_linepath:
assumes f: "continuous_on (closed_segment a b) f"
and c: "c \<in> closed_segment a b"
shows "contour_integral(linepath a b) f = contour_integral(linepath a c) f + contour_integral(linepath c b) f"
using c by (auto simp: closed_segment_def algebra_simps intro!: contour_integral_split [OF f])
subsection\<open>Reversing the order in a double path integral\<close>
text\<open>The condition is stronger than needed but it's often true in typical situations\<close>
lemma fst_im_cbox [simp]: "cbox c d \<noteq> {} \<Longrightarrow> (fst ` cbox (a,c) (b,d)) = cbox a b"
by (auto simp: cbox_Pair_eq)
lemma snd_im_cbox [simp]: "cbox a b \<noteq> {} \<Longrightarrow> (snd ` cbox (a,c) (b,d)) = cbox c d"
by (auto simp: cbox_Pair_eq)
proposition contour_integral_swap:
assumes fcon: "continuous_on (path_image g \<times> path_image h) (\<lambda>(y1,y2). f y1 y2)"
and vp: "valid_path g" "valid_path h"
and gvcon: "continuous_on {0..1} (\<lambda>t. vector_derivative g (at t))"
and hvcon: "continuous_on {0..1} (\<lambda>t. vector_derivative h (at t))"
shows "contour_integral g (\<lambda>w. contour_integral h (f w)) =
contour_integral h (\<lambda>z. contour_integral g (\<lambda>w. f w z))"
proof -
have gcon: "continuous_on {0..1} g" and hcon: "continuous_on {0..1} h"
using assms by (auto simp: valid_path_def piecewise_C1_differentiable_on_def)
have fgh1: "\<And>x. (\<lambda>t. f (g x) (h t)) = (\<lambda>(y1,y2). f y1 y2) \<circ> (\<lambda>t. (g x, h t))"
by (rule ext) simp
have fgh2: "\<And>x. (\<lambda>t. f (g t) (h x)) = (\<lambda>(y1,y2). f y1 y2) \<circ> (\<lambda>t. (g t, h x))"
by (rule ext) simp
have fcon_im1: "\<And>x. 0 \<le> x \<Longrightarrow> x \<le> 1 \<Longrightarrow> continuous_on ((\<lambda>t. (g x, h t)) ` {0..1}) (\<lambda>(x, y). f x y)"
by (rule continuous_on_subset [OF fcon]) (auto simp: path_image_def)
have fcon_im2: "\<And>x. 0 \<le> x \<Longrightarrow> x \<le> 1 \<Longrightarrow> continuous_on ((\<lambda>t. (g t, h x)) ` {0..1}) (\<lambda>(x, y). f x y)"
by (rule continuous_on_subset [OF fcon]) (auto simp: path_image_def)
have "\<And>y. y \<in> {0..1} \<Longrightarrow> continuous_on {0..1} (\<lambda>x. f (g x) (h y))"
by (subst fgh2) (rule fcon_im2 gcon continuous_intros | simp)+
then have vdg: "\<And>y. y \<in> {0..1} \<Longrightarrow> (\<lambda>x. f (g x) (h y) * vector_derivative g (at x)) integrable_on {0..1}"
using continuous_on_mult gvcon integrable_continuous_real by blast
have "(\<lambda>z. vector_derivative g (at (fst z))) = (\<lambda>x. vector_derivative g (at x)) \<circ> fst"
by auto
then have gvcon': "continuous_on (cbox (0, 0) (1, 1::real)) (\<lambda>x. vector_derivative g (at (fst x)))"
apply (rule ssubst)
apply (rule continuous_intros | simp add: gvcon)+
done
have "(\<lambda>z. vector_derivative h (at (snd z))) = (\<lambda>x. vector_derivative h (at x)) \<circ> snd"
by auto
then have hvcon': "continuous_on (cbox (0, 0) (1::real, 1)) (\<lambda>x. vector_derivative h (at (snd x)))"
apply (rule ssubst)
apply (rule continuous_intros | simp add: hvcon)+
done
have "(\<lambda>x. f (g (fst x)) (h (snd x))) = (\<lambda>(y1,y2). f y1 y2) \<circ> (\<lambda>w. ((g \<circ> fst) w, (h \<circ> snd) w))"
by auto
then have fgh: "continuous_on (cbox (0, 0) (1, 1)) (\<lambda>x. f (g (fst x)) (h (snd x)))"
apply (rule ssubst)
apply (rule gcon hcon continuous_intros | simp)+
apply (auto simp: path_image_def intro: continuous_on_subset [OF fcon])
done
have "integral {0..1} (\<lambda>x. contour_integral h (f (g x)) * vector_derivative g (at x)) =
integral {0..1} (\<lambda>x. contour_integral h (\<lambda>y. f (g x) y * vector_derivative g (at x)))"
proof (rule integral_cong [OF contour_integral_rmul [symmetric]])
show "\<And>x. x \<in> {0..1} \<Longrightarrow> f (g x) contour_integrable_on h"
unfolding contour_integrable_on
apply (rule integrable_continuous_real)
apply (rule continuous_on_mult [OF _ hvcon])
apply (subst fgh1)
apply (rule fcon_im1 hcon continuous_intros | simp)+
done
qed
also have "\<dots> = integral {0..1}
(\<lambda>y. contour_integral g (\<lambda>x. f x (h y) * vector_derivative h (at y)))"
unfolding contour_integral_integral
apply (subst integral_swap_continuous [where 'a = real and 'b = real, of 0 0 1 1, simplified])
apply (rule fgh gvcon' hvcon' continuous_intros | simp add: split_def)+
unfolding integral_mult_left [symmetric]
apply (simp only: mult_ac)
done
also have "\<dots> = contour_integral h (\<lambda>z. contour_integral g (\<lambda>w. f w z))"
unfolding contour_integral_integral
apply (rule integral_cong)
unfolding integral_mult_left [symmetric]
apply (simp add: algebra_simps)
done
finally show ?thesis
by (simp add: contour_integral_integral)
qed
lemma valid_path_negatepath: "valid_path \<gamma> \<Longrightarrow> valid_path (uminus \<circ> \<gamma>)"
unfolding o_def using piecewise_C1_differentiable_neg valid_path_def by blast
lemma has_contour_integral_negatepath:
assumes \<gamma>: "valid_path \<gamma>" and cint: "((\<lambda>z. f (- z)) has_contour_integral - i) \<gamma>"
shows "(f has_contour_integral i) (uminus \<circ> \<gamma>)"
proof -
obtain S where cont: "continuous_on {0..1} \<gamma>" and "finite S" and diff: "\<gamma> C1_differentiable_on {0..1} - S"
using \<gamma> by (auto simp: valid_path_def piecewise_C1_differentiable_on_def)
have "((\<lambda>x. - (f (- \<gamma> x) * vector_derivative \<gamma> (at x within {0..1}))) has_integral i) {0..1}"
using cint by (auto simp: has_contour_integral_def dest: has_integral_neg)
then
have "((\<lambda>x. f (- \<gamma> x) * vector_derivative (uminus \<circ> \<gamma>) (at x within {0..1})) has_integral i) {0..1}"
proof (rule rev_iffD1 [OF _ has_integral_spike_eq])
show "negligible S"
by (simp add: \<open>finite S\<close> negligible_finite)
show "f (- \<gamma> x) * vector_derivative (uminus \<circ> \<gamma>) (at x within {0..1}) =
- (f (- \<gamma> x) * vector_derivative \<gamma> (at x within {0..1}))"
if "x \<in> {0..1} - S" for x
proof -
have "vector_derivative (uminus \<circ> \<gamma>) (at x within cbox 0 1) = - vector_derivative \<gamma> (at x within cbox 0 1)"
proof (rule vector_derivative_within_cbox)
show "(uminus \<circ> \<gamma> has_vector_derivative - vector_derivative \<gamma> (at x within cbox 0 1)) (at x within cbox 0 1)"
using that unfolding o_def
by (metis C1_differentiable_on_eq UNIV_I diff differentiable_subset has_vector_derivative_minus subsetI that vector_derivative_works)
qed (use that in auto)
then show ?thesis
by simp
qed
qed
then show ?thesis by (simp add: has_contour_integral_def)
qed
lemma contour_integrable_negatepath:
assumes \<gamma>: "valid_path \<gamma>" and pi: "(\<lambda>z. f (- z)) contour_integrable_on \<gamma>"
shows "f contour_integrable_on (uminus \<circ> \<gamma>)"
by (metis \<gamma> add.inverse_inverse contour_integrable_on_def has_contour_integral_negatepath pi)
lemma C1_differentiable_polynomial_function:
fixes p :: "real \<Rightarrow> 'a::euclidean_space"
shows "polynomial_function p \<Longrightarrow> p C1_differentiable_on S"
by (metis continuous_on_polymonial_function C1_differentiable_on_def has_vector_derivative_polynomial_function)
lemma valid_path_polynomial_function:
fixes p :: "real \<Rightarrow> 'a::euclidean_space"
shows "polynomial_function p \<Longrightarrow> valid_path p"
by (force simp: valid_path_def piecewise_C1_differentiable_on_def continuous_on_polymonial_function C1_differentiable_polynomial_function)
lemma valid_path_subpath_trivial [simp]:
fixes g :: "real \<Rightarrow> 'a::euclidean_space"
shows "z \<noteq> g x \<Longrightarrow> valid_path (subpath x x g)"
by (simp add: subpath_def valid_path_polynomial_function)
subsection\<open>Partial circle path\<close>
definition\<^marker>\<open>tag important\<close> part_circlepath :: "[complex, real, real, real, real] \<Rightarrow> complex"
where "part_circlepath z r s t \<equiv> \<lambda>x. z + of_real r * exp (\<i> * of_real (linepath s t x))"
lemma pathstart_part_circlepath [simp]:
"pathstart(part_circlepath z r s t) = z + r*exp(\<i> * s)"
by (metis part_circlepath_def pathstart_def pathstart_linepath)
lemma pathfinish_part_circlepath [simp]:
"pathfinish(part_circlepath z r s t) = z + r*exp(\<i>*t)"
by (metis part_circlepath_def pathfinish_def pathfinish_linepath)
lemma reversepath_part_circlepath[simp]:
"reversepath (part_circlepath z r s t) = part_circlepath z r t s"
unfolding part_circlepath_def reversepath_def linepath_def
by (auto simp:algebra_simps)
lemma has_vector_derivative_part_circlepath [derivative_intros]:
"((part_circlepath z r s t) has_vector_derivative
(\<i> * r * (of_real t - of_real s) * exp(\<i> * linepath s t x)))
(at x within X)"
apply (simp add: part_circlepath_def linepath_def scaleR_conv_of_real)
apply (rule has_vector_derivative_real_field)
apply (rule derivative_eq_intros | simp)+
done
lemma differentiable_part_circlepath:
"part_circlepath c r a b differentiable at x within A"
using has_vector_derivative_part_circlepath[of c r a b x A] differentiableI_vector by blast
lemma vector_derivative_part_circlepath:
"vector_derivative (part_circlepath z r s t) (at x) =
\<i> * r * (of_real t - of_real s) * exp(\<i> * linepath s t x)"
using has_vector_derivative_part_circlepath vector_derivative_at by blast
lemma vector_derivative_part_circlepath01:
"\<lbrakk>0 \<le> x; x \<le> 1\<rbrakk>
\<Longrightarrow> vector_derivative (part_circlepath z r s t) (at x within {0..1}) =
\<i> * r * (of_real t - of_real s) * exp(\<i> * linepath s t x)"
using has_vector_derivative_part_circlepath
by (auto simp: vector_derivative_at_within_ivl)
lemma valid_path_part_circlepath [simp]: "valid_path (part_circlepath z r s t)"
apply (simp add: valid_path_def)
apply (rule C1_differentiable_imp_piecewise)
apply (auto simp: C1_differentiable_on_eq vector_derivative_works vector_derivative_part_circlepath has_vector_derivative_part_circlepath
intro!: continuous_intros)
done
lemma path_part_circlepath [simp]: "path (part_circlepath z r s t)"
by (simp add: valid_path_imp_path)
proposition path_image_part_circlepath:
assumes "s \<le> t"
shows "path_image (part_circlepath z r s t) = {z + r * exp(\<i> * of_real x) | x. s \<le> x \<and> x \<le> t}"
proof -
{ fix z::real
assume "0 \<le> z" "z \<le> 1"
with \<open>s \<le> t\<close> have "\<exists>x. (exp (\<i> * linepath s t z) = exp (\<i> * of_real x)) \<and> s \<le> x \<and> x \<le> t"
apply (rule_tac x="(1 - z) * s + z * t" in exI)
apply (simp add: linepath_def scaleR_conv_of_real algebra_simps)
apply (rule conjI)
using mult_right_mono apply blast
using affine_ineq by (metis "mult.commute")
}
moreover
{ fix z
assume "s \<le> z" "z \<le> t"
then have "z + of_real r * exp (\<i> * of_real z) \<in> (\<lambda>x. z + of_real r * exp (\<i> * linepath s t x)) ` {0..1}"
apply (rule_tac x="(z - s)/(t - s)" in image_eqI)
apply (simp add: linepath_def scaleR_conv_of_real divide_simps exp_eq)
apply (auto simp: field_split_simps)
done
}
ultimately show ?thesis
by (fastforce simp add: path_image_def part_circlepath_def)
qed
lemma path_image_part_circlepath':
"path_image (part_circlepath z r s t) = (\<lambda>x. z + r * cis x) ` closed_segment s t"
proof -
have "path_image (part_circlepath z r s t) =
(\<lambda>x. z + r * exp(\<i> * of_real x)) ` linepath s t ` {0..1}"
by (simp add: image_image path_image_def part_circlepath_def)
also have "linepath s t ` {0..1} = closed_segment s t"
by (rule linepath_image_01)
finally show ?thesis by (simp add: cis_conv_exp)
qed
lemma path_image_part_circlepath_subset:
"\<lbrakk>s \<le> t; 0 \<le> r\<rbrakk> \<Longrightarrow> path_image(part_circlepath z r s t) \<subseteq> sphere z r"
by (auto simp: path_image_part_circlepath sphere_def dist_norm algebra_simps norm_mult)
lemma in_path_image_part_circlepath:
assumes "w \<in> path_image(part_circlepath z r s t)" "s \<le> t" "0 \<le> r"
shows "norm(w - z) = r"
proof -
have "w \<in> {c. dist z c = r}"
by (metis (no_types) path_image_part_circlepath_subset sphere_def subset_eq assms)
thus ?thesis
by (simp add: dist_norm norm_minus_commute)
qed
lemma path_image_part_circlepath_subset':
assumes "r \<ge> 0"
shows "path_image (part_circlepath z r s t) \<subseteq> sphere z r"
proof (cases "s \<le> t")
case True
thus ?thesis using path_image_part_circlepath_subset[of s t r z] assms by simp
next
case False
thus ?thesis using path_image_part_circlepath_subset[of t s r z] assms
by (subst reversepath_part_circlepath [symmetric], subst path_image_reversepath) simp_all
qed
lemma part_circlepath_cnj: "cnj (part_circlepath c r a b x) = part_circlepath (cnj c) r (-a) (-b) x"
by (simp add: part_circlepath_def exp_cnj linepath_def algebra_simps)
lemma contour_integral_bound_part_circlepath:
assumes "f contour_integrable_on part_circlepath c r a b"
assumes "B \<ge> 0" "r \<ge> 0" "\<And>x. x \<in> path_image (part_circlepath c r a b) \<Longrightarrow> norm (f x) \<le> B"
shows "norm (contour_integral (part_circlepath c r a b) f) \<le> B * r * \<bar>b - a\<bar>"
proof -
let ?I = "integral {0..1} (\<lambda>x. f (part_circlepath c r a b x) * \<i> * of_real (r * (b - a)) *
exp (\<i> * linepath a b x))"
have "norm ?I \<le> integral {0..1} (\<lambda>x::real. B * 1 * (r * \<bar>b - a\<bar>) * 1)"
proof (rule integral_norm_bound_integral, goal_cases)
case 1
with assms(1) show ?case
by (simp add: contour_integrable_on vector_derivative_part_circlepath mult_ac)
next
case (3 x)
with assms(2-) show ?case unfolding norm_mult norm_of_real abs_mult
by (intro mult_mono) (auto simp: path_image_def)
qed auto
also have "?I = contour_integral (part_circlepath c r a b) f"
by (simp add: contour_integral_integral vector_derivative_part_circlepath mult_ac)
finally show ?thesis by simp
qed
lemma has_contour_integral_part_circlepath_iff:
assumes "a < b"
shows "(f has_contour_integral I) (part_circlepath c r a b) \<longleftrightarrow>
((\<lambda>t. f (c + r * cis t) * r * \<i> * cis t) has_integral I) {a..b}"
proof -
have "(f has_contour_integral I) (part_circlepath c r a b) \<longleftrightarrow>
((\<lambda>x. f (part_circlepath c r a b x) * vector_derivative (part_circlepath c r a b)
(at x within {0..1})) has_integral I) {0..1}"
unfolding has_contour_integral_def ..
also have "\<dots> \<longleftrightarrow> ((\<lambda>x. f (part_circlepath c r a b x) * r * (b - a) * \<i> *
cis (linepath a b x)) has_integral I) {0..1}"
by (intro has_integral_cong, subst vector_derivative_part_circlepath01)
(simp_all add: cis_conv_exp)
also have "\<dots> \<longleftrightarrow> ((\<lambda>x. f (c + r * exp (\<i> * linepath (of_real a) (of_real b) x)) *
r * \<i> * exp (\<i> * linepath (of_real a) (of_real b) x) *
vector_derivative (linepath (of_real a) (of_real b))
(at x within {0..1})) has_integral I) {0..1}"
by (intro has_integral_cong, subst vector_derivative_linepath_within)
(auto simp: part_circlepath_def cis_conv_exp of_real_linepath [symmetric])
also have "\<dots> \<longleftrightarrow> ((\<lambda>z. f (c + r * exp (\<i> * z)) * r * \<i> * exp (\<i> * z)) has_contour_integral I)
(linepath (of_real a) (of_real b))"
by (simp add: has_contour_integral_def)
also have "\<dots> \<longleftrightarrow> ((\<lambda>t. f (c + r * cis t) * r * \<i> * cis t) has_integral I) {a..b}" using assms
by (subst has_contour_integral_linepath_Reals_iff) (simp_all add: cis_conv_exp)
finally show ?thesis .
qed
lemma contour_integrable_part_circlepath_iff:
assumes "a < b"
shows "f contour_integrable_on (part_circlepath c r a b) \<longleftrightarrow>
(\<lambda>t. f (c + r * cis t) * r * \<i> * cis t) integrable_on {a..b}"
using assms by (auto simp: contour_integrable_on_def integrable_on_def
has_contour_integral_part_circlepath_iff)
lemma contour_integral_part_circlepath_eq:
assumes "a < b"
shows "contour_integral (part_circlepath c r a b) f =
integral {a..b} (\<lambda>t. f (c + r * cis t) * r * \<i> * cis t)"
proof (cases "f contour_integrable_on part_circlepath c r a b")
case True
hence "(\<lambda>t. f (c + r * cis t) * r * \<i> * cis t) integrable_on {a..b}"
using assms by (simp add: contour_integrable_part_circlepath_iff)
with True show ?thesis
using has_contour_integral_part_circlepath_iff[OF assms]
contour_integral_unique has_integral_integrable_integral by blast
next
case False
hence "\<not>(\<lambda>t. f (c + r * cis t) * r * \<i> * cis t) integrable_on {a..b}"
using assms by (simp add: contour_integrable_part_circlepath_iff)
with False show ?thesis
by (simp add: not_integrable_contour_integral not_integrable_integral)
qed
lemma contour_integral_part_circlepath_reverse:
"contour_integral (part_circlepath c r a b) f = -contour_integral (part_circlepath c r b a) f"
by (subst reversepath_part_circlepath [symmetric], subst contour_integral_reversepath) simp_all
lemma contour_integral_part_circlepath_reverse':
"b < a \<Longrightarrow> contour_integral (part_circlepath c r a b) f =
-contour_integral (part_circlepath c r b a) f"
by (rule contour_integral_part_circlepath_reverse)
lemma finite_bounded_log: "finite {z::complex. norm z \<le> b \<and> exp z = w}"
proof (cases "w = 0")
case True then show ?thesis by auto
next
case False
have *: "finite {x. cmod (complex_of_real (2 * real_of_int x * pi) * \<i>) \<le> b + cmod (Ln w)}"
apply (simp add: norm_mult finite_int_iff_bounded_le)
apply (rule_tac x="\<lfloor>(b + cmod (Ln w)) / (2*pi)\<rfloor>" in exI)
apply (auto simp: field_split_simps le_floor_iff)
done
have [simp]: "\<And>P f. {z. P z \<and> (\<exists>n. z = f n)} = f ` {n. P (f n)}"
by blast
show ?thesis
apply (subst exp_Ln [OF False, symmetric])
apply (simp add: exp_eq)
using norm_add_leD apply (fastforce intro: finite_subset [OF _ *])
done
qed
lemma finite_bounded_log2:
fixes a::complex
assumes "a \<noteq> 0"
shows "finite {z. norm z \<le> b \<and> exp(a*z) = w}"
proof -
have *: "finite ((\<lambda>z. z / a) ` {z. cmod z \<le> b * cmod a \<and> exp z = w})"
by (rule finite_imageI [OF finite_bounded_log])
show ?thesis
by (rule finite_subset [OF _ *]) (force simp: assms norm_mult)
qed
lemma has_contour_integral_bound_part_circlepath_strong:
assumes fi: "(f has_contour_integral i) (part_circlepath z r s t)"
and "finite k" and le: "0 \<le> B" "0 < r" "s \<le> t"
and B: "\<And>x. x \<in> path_image(part_circlepath z r s t) - k \<Longrightarrow> norm(f x) \<le> B"
shows "cmod i \<le> B * r * (t - s)"
proof -
consider "s = t" | "s < t" using \<open>s \<le> t\<close> by linarith
then show ?thesis
proof cases
case 1 with fi [unfolded has_contour_integral]
have "i = 0" by (simp add: vector_derivative_part_circlepath)
with assms show ?thesis by simp
next
case 2
have [simp]: "\<bar>r\<bar> = r" using \<open>r > 0\<close> by linarith
have [simp]: "cmod (complex_of_real t - complex_of_real s) = t-s"
by (metis "2" abs_of_pos diff_gt_0_iff_gt norm_of_real of_real_diff)
have "finite (part_circlepath z r s t -` {y} \<inter> {0..1})" if "y \<in> k" for y
proof -
define w where "w = (y - z)/of_real r / exp(\<i> * of_real s)"
have fin: "finite (of_real -` {z. cmod z \<le> 1 \<and> exp (\<i> * complex_of_real (t - s) * z) = w})"
apply (rule finite_vimageI [OF finite_bounded_log2])
using \<open>s < t\<close> apply (auto simp: inj_of_real)
done
show ?thesis
apply (simp add: part_circlepath_def linepath_def vimage_def)
apply (rule finite_subset [OF _ fin])
using le
apply (auto simp: w_def algebra_simps scaleR_conv_of_real exp_add exp_diff)
done
qed
then have fin01: "finite ((part_circlepath z r s t) -` k \<inter> {0..1})"
by (rule finite_finite_vimage_IntI [OF \<open>finite k\<close>])
have **: "((\<lambda>x. if (part_circlepath z r s t x) \<in> k then 0
else f(part_circlepath z r s t x) *
vector_derivative (part_circlepath z r s t) (at x)) has_integral i) {0..1}"
by (rule has_integral_spike [OF negligible_finite [OF fin01]]) (use fi has_contour_integral in auto)
have *: "\<And>x. \<lbrakk>0 \<le> x; x \<le> 1; part_circlepath z r s t x \<notin> k\<rbrakk> \<Longrightarrow> cmod (f (part_circlepath z r s t x)) \<le> B"
by (auto intro!: B [unfolded path_image_def image_def, simplified])
show ?thesis
apply (rule has_integral_bound [where 'a=real, simplified, OF _ **, simplified])
using assms apply force
apply (simp add: norm_mult vector_derivative_part_circlepath)
using le * "2" \<open>r > 0\<close> by auto
qed
qed
lemma has_contour_integral_bound_part_circlepath:
"\<lbrakk>(f has_contour_integral i) (part_circlepath z r s t);
0 \<le> B; 0 < r; s \<le> t;
\<And>x. x \<in> path_image(part_circlepath z r s t) \<Longrightarrow> norm(f x) \<le> B\<rbrakk>
\<Longrightarrow> norm i \<le> B*r*(t - s)"
by (auto intro: has_contour_integral_bound_part_circlepath_strong)
lemma contour_integrable_continuous_part_circlepath:
"continuous_on (path_image (part_circlepath z r s t)) f
\<Longrightarrow> f contour_integrable_on (part_circlepath z r s t)"
apply (simp add: contour_integrable_on has_contour_integral_def vector_derivative_part_circlepath path_image_def)
apply (rule integrable_continuous_real)
apply (fast intro: path_part_circlepath [unfolded path_def] continuous_intros continuous_on_compose2 [where g=f, OF _ _ order_refl])
done
lemma simple_path_part_circlepath:
"simple_path(part_circlepath z r s t) \<longleftrightarrow> (r \<noteq> 0 \<and> s \<noteq> t \<and> \<bar>s - t\<bar> \<le> 2*pi)"
proof (cases "r = 0 \<or> s = t")
case True
then show ?thesis
unfolding part_circlepath_def simple_path_def
by (rule disjE) (force intro: bexI [where x = "1/4"] bexI [where x = "1/3"])+
next
case False then have "r \<noteq> 0" "s \<noteq> t" by auto
have *: "\<And>x y z s t. \<i>*((1 - x) * s + x * t) = \<i>*(((1 - y) * s + y * t)) + z \<longleftrightarrow> \<i>*(x - y) * (t - s) = z"
by (simp add: algebra_simps)
have abs01: "\<And>x y::real. 0 \<le> x \<and> x \<le> 1 \<and> 0 \<le> y \<and> y \<le> 1
\<Longrightarrow> (x = y \<or> x = 0 \<and> y = 1 \<or> x = 1 \<and> y = 0 \<longleftrightarrow> \<bar>x - y\<bar> \<in> {0,1})"
by auto
have **: "\<And>x y. (\<exists>n. (complex_of_real x - of_real y) * (of_real t - of_real s) = 2 * (of_int n * of_real pi)) \<longleftrightarrow>
(\<exists>n. \<bar>x - y\<bar> * (t - s) = 2 * (of_int n * pi))"
by (force simp: algebra_simps abs_if dest: arg_cong [where f=Re] arg_cong [where f=complex_of_real]
intro: exI [where x = "-n" for n])
have 1: "\<bar>s - t\<bar> \<le> 2 * pi"
if "\<And>x. 0 \<le> x \<and> x \<le> 1 \<Longrightarrow> (\<exists>n. x * (t - s) = 2 * (real_of_int n * pi)) \<longrightarrow> x = 0 \<or> x = 1"
proof (rule ccontr)
assume "\<not> \<bar>s - t\<bar> \<le> 2 * pi"
then have *: "\<And>n. t - s \<noteq> of_int n * \<bar>s - t\<bar>"
using False that [of "2*pi / \<bar>t - s\<bar>"]
by (simp add: abs_minus_commute divide_simps)
show False
using * [of 1] * [of "-1"] by auto
qed
have 2: "\<bar>s - t\<bar> = \<bar>2 * (real_of_int n * pi) / x\<bar>" if "x \<noteq> 0" "x * (t - s) = 2 * (real_of_int n * pi)" for x n
proof -
have "t-s = 2 * (real_of_int n * pi)/x"
using that by (simp add: field_simps)
then show ?thesis by (metis abs_minus_commute)
qed
have abs_away: "\<And>P. (\<forall>x\<in>{0..1}. \<forall>y\<in>{0..1}. P \<bar>x - y\<bar>) \<longleftrightarrow> (\<forall>x::real. 0 \<le> x \<and> x \<le> 1 \<longrightarrow> P x)"
by force
show ?thesis using False
apply (simp add: simple_path_def)
apply (simp add: part_circlepath_def linepath_def exp_eq * ** abs01 del: Set.insert_iff)
apply (subst abs_away)
apply (auto simp: 1)
apply (rule ccontr)
apply (auto simp: 2 field_split_simps abs_mult dest: of_int_leD)
done
qed
lemma arc_part_circlepath:
assumes "r \<noteq> 0" "s \<noteq> t" "\<bar>s - t\<bar> < 2*pi"
shows "arc (part_circlepath z r s t)"
proof -
have *: "x = y" if eq: "\<i> * (linepath s t x) = \<i> * (linepath s t y) + 2 * of_int n * complex_of_real pi * \<i>"
and x: "x \<in> {0..1}" and y: "y \<in> {0..1}" for x y n
proof (rule ccontr)
assume "x \<noteq> y"
have "(linepath s t x) = (linepath s t y) + 2 * of_int n * complex_of_real pi"
by (metis add_divide_eq_iff complex_i_not_zero mult.commute nonzero_mult_div_cancel_left eq)
then have "s*y + t*x = s*x + (t*y + of_int n * (pi * 2))"
by (force simp: algebra_simps linepath_def dest: arg_cong [where f=Re])
with \<open>x \<noteq> y\<close> have st: "s-t = (of_int n * (pi * 2) / (y-x))"
by (force simp: field_simps)
have "\<bar>real_of_int n\<bar> < \<bar>y - x\<bar>"
using assms \<open>x \<noteq> y\<close> by (simp add: st abs_mult field_simps)
then show False
using assms x y st by (auto dest: of_int_lessD)
qed
show ?thesis
using assms
apply (simp add: arc_def)
apply (simp add: part_circlepath_def inj_on_def exp_eq)
apply (blast intro: *)
done
qed
subsection\<open>Special case of one complete circle\<close>
definition\<^marker>\<open>tag important\<close> circlepath :: "[complex, real, real] \<Rightarrow> complex"
where "circlepath z r \<equiv> part_circlepath z r 0 (2*pi)"
lemma circlepath: "circlepath z r = (\<lambda>x. z + r * exp(2 * of_real pi * \<i> * of_real x))"
by (simp add: circlepath_def part_circlepath_def linepath_def algebra_simps)
lemma pathstart_circlepath [simp]: "pathstart (circlepath z r) = z + r"
by (simp add: circlepath_def)
lemma pathfinish_circlepath [simp]: "pathfinish (circlepath z r) = z + r"
by (simp add: circlepath_def) (metis exp_two_pi_i mult.commute)
lemma circlepath_minus: "circlepath z (-r) x = circlepath z r (x + 1/2)"
proof -
have "z + of_real r * exp (2 * pi * \<i> * (x + 1/2)) =
z + of_real r * exp (2 * pi * \<i> * x + pi * \<i>)"
by (simp add: divide_simps) (simp add: algebra_simps)
also have "\<dots> = z - r * exp (2 * pi * \<i> * x)"
by (simp add: exp_add)
finally show ?thesis
by (simp add: circlepath path_image_def sphere_def dist_norm)
qed
lemma circlepath_add1: "circlepath z r (x+1) = circlepath z r x"
using circlepath_minus [of z r "x+1/2"] circlepath_minus [of z "-r" x]
by (simp add: add.commute)
lemma circlepath_add_half: "circlepath z r (x + 1/2) = circlepath z r (x - 1/2)"
using circlepath_add1 [of z r "x-1/2"]
by (simp add: add.commute)
lemma path_image_circlepath_minus_subset:
"path_image (circlepath z (-r)) \<subseteq> path_image (circlepath z r)"
apply (simp add: path_image_def image_def circlepath_minus, clarify)
apply (case_tac "xa \<le> 1/2", force)
apply (force simp: circlepath_add_half)+
done
lemma path_image_circlepath_minus: "path_image (circlepath z (-r)) = path_image (circlepath z r)"
using path_image_circlepath_minus_subset by fastforce
lemma has_vector_derivative_circlepath [derivative_intros]:
"((circlepath z r) has_vector_derivative (2 * pi * \<i> * r * exp (2 * of_real pi * \<i> * of_real x)))
(at x within X)"
apply (simp add: circlepath_def scaleR_conv_of_real)
apply (rule derivative_eq_intros)
apply (simp add: algebra_simps)
done
lemma vector_derivative_circlepath:
"vector_derivative (circlepath z r) (at x) =
2 * pi * \<i> * r * exp(2 * of_real pi * \<i> * x)"
using has_vector_derivative_circlepath vector_derivative_at by blast
lemma vector_derivative_circlepath01:
"\<lbrakk>0 \<le> x; x \<le> 1\<rbrakk>
\<Longrightarrow> vector_derivative (circlepath z r) (at x within {0..1}) =
2 * pi * \<i> * r * exp(2 * of_real pi * \<i> * x)"
using has_vector_derivative_circlepath
by (auto simp: vector_derivative_at_within_ivl)
lemma valid_path_circlepath [simp]: "valid_path (circlepath z r)"
by (simp add: circlepath_def)
lemma path_circlepath [simp]: "path (circlepath z r)"
by (simp add: valid_path_imp_path)
lemma path_image_circlepath_nonneg:
assumes "0 \<le> r" shows "path_image (circlepath z r) = sphere z r"
proof -
have *: "x \<in> (\<lambda>u. z + (cmod (x - z)) * exp (\<i> * (of_real u * (of_real pi * 2)))) ` {0..1}" for x
proof (cases "x = z")
case True then show ?thesis by force
next
case False
define w where "w = x - z"
then have "w \<noteq> 0" by (simp add: False)
have **: "\<And>t. \<lbrakk>Re w = cos t * cmod w; Im w = sin t * cmod w\<rbrakk> \<Longrightarrow> w = of_real (cmod w) * exp (\<i> * t)"
using cis_conv_exp complex_eq_iff by auto
show ?thesis
apply (rule sincos_total_2pi [of "Re(w/of_real(norm w))" "Im(w/of_real(norm w))"])
apply (simp add: divide_simps \<open>w \<noteq> 0\<close> cmod_power2 [symmetric])
apply (rule_tac x="t / (2*pi)" in image_eqI)
apply (simp add: field_simps \<open>w \<noteq> 0\<close>)
using False **
apply (auto simp: w_def)
done
qed
show ?thesis
unfolding circlepath path_image_def sphere_def dist_norm
by (force simp: assms algebra_simps norm_mult norm_minus_commute intro: *)
qed
lemma path_image_circlepath [simp]:
"path_image (circlepath z r) = sphere z \<bar>r\<bar>"
using path_image_circlepath_minus
by (force simp: path_image_circlepath_nonneg abs_if)
lemma has_contour_integral_bound_circlepath_strong:
"\<lbrakk>(f has_contour_integral i) (circlepath z r);
finite k; 0 \<le> B; 0 < r;
\<And>x. \<lbrakk>norm(x - z) = r; x \<notin> k\<rbrakk> \<Longrightarrow> norm(f x) \<le> B\<rbrakk>
\<Longrightarrow> norm i \<le> B*(2*pi*r)"
unfolding circlepath_def
by (auto simp: algebra_simps in_path_image_part_circlepath dest!: has_contour_integral_bound_part_circlepath_strong)
lemma has_contour_integral_bound_circlepath:
"\<lbrakk>(f has_contour_integral i) (circlepath z r);
0 \<le> B; 0 < r; \<And>x. norm(x - z) = r \<Longrightarrow> norm(f x) \<le> B\<rbrakk>
\<Longrightarrow> norm i \<le> B*(2*pi*r)"
by (auto intro: has_contour_integral_bound_circlepath_strong)
lemma contour_integrable_continuous_circlepath:
"continuous_on (path_image (circlepath z r)) f
\<Longrightarrow> f contour_integrable_on (circlepath z r)"
by (simp add: circlepath_def contour_integrable_continuous_part_circlepath)
lemma simple_path_circlepath: "simple_path(circlepath z r) \<longleftrightarrow> (r \<noteq> 0)"
by (simp add: circlepath_def simple_path_part_circlepath)
lemma notin_path_image_circlepath [simp]: "cmod (w - z) < r \<Longrightarrow> w \<notin> path_image (circlepath z r)"
by (simp add: sphere_def dist_norm norm_minus_commute)
lemma contour_integral_circlepath:
assumes "r > 0"
shows "contour_integral (circlepath z r) (\<lambda>w. 1 / (w - z)) = 2 * complex_of_real pi * \<i>"
proof (rule contour_integral_unique)
show "((\<lambda>w. 1 / (w - z)) has_contour_integral 2 * complex_of_real pi * \<i>) (circlepath z r)"
unfolding has_contour_integral_def using assms
apply (subst has_integral_cong)
apply (simp add: vector_derivative_circlepath01)
using has_integral_const_real [of _ 0 1] apply (force simp: circlepath)
done
qed
subsection\<open> Uniform convergence of path integral\<close>
text\<open>Uniform convergence when the derivative of the path is bounded, and in particular for the special case of a circle.\<close>
proposition contour_integral_uniform_limit:
assumes ev_fint: "eventually (\<lambda>n::'a. (f n) contour_integrable_on \<gamma>) F"
and ul_f: "uniform_limit (path_image \<gamma>) f l F"
and noleB: "\<And>t. t \<in> {0..1} \<Longrightarrow> norm (vector_derivative \<gamma> (at t)) \<le> B"
and \<gamma>: "valid_path \<gamma>"
and [simp]: "\<not> trivial_limit F"
shows "l contour_integrable_on \<gamma>" "((\<lambda>n. contour_integral \<gamma> (f n)) \<longlongrightarrow> contour_integral \<gamma> l) F"
proof -
have "0 \<le> B" by (meson noleB [of 0] atLeastAtMost_iff norm_ge_zero order_refl order_trans zero_le_one)
{ fix e::real
assume "0 < e"
then have "0 < e / (\<bar>B\<bar> + 1)" by simp
then have "\<forall>\<^sub>F n in F. \<forall>x\<in>path_image \<gamma>. cmod (f n x - l x) < e / (\<bar>B\<bar> + 1)"
using ul_f [unfolded uniform_limit_iff dist_norm] by auto
with ev_fint
obtain a where fga: "\<And>x. x \<in> {0..1} \<Longrightarrow> cmod (f a (\<gamma> x) - l (\<gamma> x)) < e / (\<bar>B\<bar> + 1)"
and inta: "(\<lambda>t. f a (\<gamma> t) * vector_derivative \<gamma> (at t)) integrable_on {0..1}"
using eventually_happens [OF eventually_conj]
by (fastforce simp: contour_integrable_on path_image_def)
have Ble: "B * e / (\<bar>B\<bar> + 1) \<le> e"
using \<open>0 \<le> B\<close> \<open>0 < e\<close> by (simp add: field_split_simps)
have "\<exists>h. (\<forall>x\<in>{0..1}. cmod (l (\<gamma> x) * vector_derivative \<gamma> (at x) - h x) \<le> e) \<and> h integrable_on {0..1}"
proof (intro exI conjI ballI)
show "cmod (l (\<gamma> x) * vector_derivative \<gamma> (at x) - f a (\<gamma> x) * vector_derivative \<gamma> (at x)) \<le> e"
if "x \<in> {0..1}" for x
apply (rule order_trans [OF _ Ble])
using noleB [OF that] fga [OF that] \<open>0 \<le> B\<close> \<open>0 < e\<close>
apply (simp add: norm_mult left_diff_distrib [symmetric] norm_minus_commute divide_simps)
apply (fastforce simp: mult_ac dest: mult_mono [OF less_imp_le])
done
qed (rule inta)
}
then show lintg: "l contour_integrable_on \<gamma>"
unfolding contour_integrable_on by (metis (mono_tags, lifting)integrable_uniform_limit_real)
{ fix e::real
define B' where "B' = B + 1"
have B': "B' > 0" "B' > B" using \<open>0 \<le> B\<close> by (auto simp: B'_def)
assume "0 < e"
then have ev_no': "\<forall>\<^sub>F n in F. \<forall>x\<in>path_image \<gamma>. 2 * cmod (f n x - l x) < e / B'"
using ul_f [unfolded uniform_limit_iff dist_norm, rule_format, of "e / B' / 2"] B'
by (simp add: field_simps)
have ie: "integral {0..1::real} (\<lambda>x. e / 2) < e" using \<open>0 < e\<close> by simp
have *: "cmod (f x (\<gamma> t) * vector_derivative \<gamma> (at t) - l (\<gamma> t) * vector_derivative \<gamma> (at t)) \<le> e / 2"
if t: "t\<in>{0..1}" and leB': "2 * cmod (f x (\<gamma> t) - l (\<gamma> t)) < e / B'" for x t
proof -
have "2 * cmod (f x (\<gamma> t) - l (\<gamma> t)) * cmod (vector_derivative \<gamma> (at t)) \<le> e * (B/ B')"
using mult_mono [OF less_imp_le [OF leB'] noleB] B' \<open>0 < e\<close> t by auto
also have "\<dots> < e"
by (simp add: B' \<open>0 < e\<close> mult_imp_div_pos_less)
finally have "2 * cmod (f x (\<gamma> t) - l (\<gamma> t)) * cmod (vector_derivative \<gamma> (at t)) < e" .
then show ?thesis
by (simp add: left_diff_distrib [symmetric] norm_mult)
qed
have le_e: "\<And>x. \<lbrakk>\<forall>xa\<in>{0..1}. 2 * cmod (f x (\<gamma> xa) - l (\<gamma> xa)) < e / B'; f x contour_integrable_on \<gamma>\<rbrakk>
\<Longrightarrow> cmod (integral {0..1}
(\<lambda>u. f x (\<gamma> u) * vector_derivative \<gamma> (at u) - l (\<gamma> u) * vector_derivative \<gamma> (at u))) < e"
apply (rule le_less_trans [OF integral_norm_bound_integral ie])
apply (simp add: lintg integrable_diff contour_integrable_on [symmetric])
apply (blast intro: *)+
done
have "\<forall>\<^sub>F x in F. dist (contour_integral \<gamma> (f x)) (contour_integral \<gamma> l) < e"
apply (rule eventually_mono [OF eventually_conj [OF ev_no' ev_fint]])
apply (simp add: dist_norm contour_integrable_on path_image_def contour_integral_integral)
apply (simp add: lintg integral_diff [symmetric] contour_integrable_on [symmetric] le_e)
done
}
then show "((\<lambda>n. contour_integral \<gamma> (f n)) \<longlongrightarrow> contour_integral \<gamma> l) F"
by (rule tendstoI)
qed
corollary\<^marker>\<open>tag unimportant\<close> contour_integral_uniform_limit_circlepath:
assumes "\<forall>\<^sub>F n::'a in F. (f n) contour_integrable_on (circlepath z r)"
and "uniform_limit (sphere z r) f l F"
and "\<not> trivial_limit F" "0 < r"
shows "l contour_integrable_on (circlepath z r)"
"((\<lambda>n. contour_integral (circlepath z r) (f n)) \<longlongrightarrow> contour_integral (circlepath z r) l) F"
using assms by (auto simp: vector_derivative_circlepath norm_mult intro!: contour_integral_uniform_limit)
end