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SKolodynski committed Jul 24, 2024
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17 changes: 10 additions & 7 deletions IsarMathLib/Group_ZF_5.thy
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Expand Up @@ -49,8 +49,8 @@ definition
"IsMorphism(G,P,F,f) \<equiv> \<forall>g\<^sub>1\<in>G. \<forall>g\<^sub>2\<in>G. f`(P`\<langle>g\<^sub>1,g\<^sub>2\<rangle>) = F`\<langle>f`(g\<^sub>1),f`(g\<^sub>2)\<rangle>"

text\<open>A function $f:G\rightarrow H$ between algebraic structures
$(G,\cdot_G)$ and $(H,\cdot_H)$ with one operation (each) is a homomorphism is it has the morphism
property. \<close>
$(G,\cdot_G)$ and $(H,\cdot_H)$ with one operation (each) is a homomorphism if
it has the morphism property. \<close>

definition
"Homomor(f,G,P,H,F) \<equiv> f:G\<rightarrow>H \<and> IsMorphism(G,P,F,f)"
Expand All @@ -62,8 +62,10 @@ lemma homomor_eq:
shows "f`(P`\<langle>g\<^sub>1,g\<^sub>2\<rangle>) = F`\<langle>f`(g\<^sub>1),f`(g\<^sub>2)\<rangle>"
using assms unfolding Homomor_def IsMorphism_def by auto

text\<open>An endomorphism is a homomorphism from a group to the same group. In case
the group is abelian, it has a nice structure.\<close>
text\<open>An endomorphism is a homomorphism from a group to the same group.
We define \<open>End(G,P)\<close> as the set of endomorphisms for a given group.
As we show later when the group is abelian, the set of endomorphisms
with pointwise adddition and composition as multiplication forms a ring.\<close>

definition
"End(G,P) \<equiv> {f\<in>G\<rightarrow>G. Homomor(f,G,P,G,P)}"
Expand Down Expand Up @@ -108,7 +110,7 @@ abbreviation InEnd("_ {in End} [_,_]")
where "InEnd(F,G,P) \<equiv> restrict(F,End(G,P)\<times>End(G,P))"

text\<open>Endomoprhisms of a group form a monoid with composition as the binary operation,
with the identity map as the neutral element.\<close>
and the identity map as the neutral element.\<close>

theorem (in group0) end_comp_monoid:
shows "IsAmonoid(End(G,P),InEnd(Composition(G),G,P))"
Expand Down Expand Up @@ -139,7 +141,8 @@ text\<open>The set of endomorphisms is closed under pointwise addition (derived
This is so because the group is abelian.\<close>

theorem (in abelian_group) end_pointwise_addition:
assumes "f\<in>End(G,P)" "g\<in>End(G,P)" "F = P {lifted to function space over} G"
assumes "f\<in>End(G,P)" "g\<in>End(G,P)"
defines "F \<equiv> P {lifted to function space over} G"
shows "F`\<langle>f,g\<rangle> \<in> End(G,P)"
proof-
from assms(1,2) have fun: "f:G\<rightarrow>G" "g\<in>G\<rightarrow>G" unfolding End_def by simp_all
Expand All @@ -161,7 +164,7 @@ lemma (in abelian_group) end_pointwise_add_val:
using assms group_oper_fun monoid.group0_1_L3B func_ZF_1_L4
unfolding End_def by simp

text\<open>The inverse of an abelian group is an endomorphism.\<close>
text\<open>The operation of taking the inverse in an abelian group is an endomorphism.\<close>

lemma (in abelian_group) end_inverse_group:
shows "GroupInv(G,P) \<in> End(G,P)"
Expand Down
3 changes: 2 additions & 1 deletion IsarMathLib/MetricSpace_ZF.thy
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Expand Up @@ -531,7 +531,8 @@ lemma (in pmetric_space) gauge_6thCond:

text\<open>The remaining 4th condition for the sets of the form $d^{-1}([0,b])$
to be a uniform base (or a fundamental system of entourages) cannot be proven
without additional assumptions. To see that consider the example
without additional assumptions in the context of ordered loop valued metrics.
To see that consider the example
of natural numbers with the metric $d\langle x,y \rangle = |x-y|$, where we think
of $d$ as valued in the nonnegative set of ordered group of integers.
Now take the set $B_1 = d^{-1}([0,1]) = d^{-1}(\{ 0,1\} )$. Then the set $B_1 \circ B_1$
Expand Down
2 changes: 1 addition & 1 deletion IsarMathLib/UniformSpace_ZF.thy
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Expand Up @@ -526,7 +526,7 @@ qed

subsection\<open> Base of a uniformity \<close>

text\<open>A \<open>base\<close> or a \<open>fundamental systems of entourages\<close> of a uniformity $\Phi$ is
text\<open>A \<open>base\<close> or a \<open>fundamental system of entourages\<close> of a uniformity $\Phi$ is
a subset of $\Phi$ that is sufficient to uniquely determine it. This is
analogous to the notion of a base of a topology (see \<open>Topology_ZF_1\<close> or a base of a filter
(see \<open>Topology_ZF_4\<close>). \<close>
Expand Down
8 changes: 4 additions & 4 deletions isar2html2.0/isarhtml/index.html
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Expand Up @@ -213,18 +213,18 @@ <h3>About this site</h3>

<p><a href="Topology_ZF_8.html">Topology_ZF_8</a></p>

<p><a href="MetricSpace_ZF.html">MetricSpace_ZF</a></p>

<p><a href="Real_ZF_2.html">Real_ZF_2</a></p>

<p><a href="MetricSpace_ZF_1.html">Real_ZF_2</a></p>

<p><a href="UniformSpace_ZF.html">UniformSpace_ZF</a></p>

<p><a href="UniformSpace_ZF_1.html">UniformSpace_ZF_1</a></p>

<p><a href="UniformSpace_ZF_2.html">UniformSpace_ZF_2</a></p>

<p><a href="MetricSpace_ZF.html">MetricSpace_ZF</a></p>

<p><a href="MetricSpace_ZF_1.html">MetricSpace_ZF_1</a></p>

<p><a href="TopologicalGroup_ZF.html">TopologicalGroup_ZF</a></p>

<p><a href="TopologicalGroup_Uniformity_ZF.html">TopGroup_Uniformity_ZF</a></p>
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4 changes: 2 additions & 2 deletions isar2html2.0/theories.conf
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Expand Up @@ -68,12 +68,12 @@ Topology_ZF_4a
Topology_ZF_6
Topology_ZF_8
Topology_ZF_examples
MetricSpace_ZF
Real_ZF_2
MetricSpace_ZF_1
UniformSpace_ZF
UniformSpace_ZF_1
UniformSpace_ZF_2
MetricSpace_ZF
MetricSpace_ZF_1
TopologicalGroup_ZF
TopologicalGroup_Uniformity_ZF
MMI_prelude
Expand Down

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