diff options
Diffstat (limited to 'library/topology')
| -rw-r--r-- | library/topology/real-topological-space.tex | 26 | ||||
| -rw-r--r-- | library/topology/urysohn2.tex | 108 |
2 files changed, 85 insertions, 49 deletions
diff --git a/library/topology/real-topological-space.tex b/library/topology/real-topological-space.tex new file mode 100644 index 0000000..239965c --- /dev/null +++ b/library/topology/real-topological-space.tex @@ -0,0 +1,26 @@ +\import{set.tex} +\import{set/cons.tex} +\import{set/powerset.tex} +\import{set/fixpoint.tex} +\import{set/product.tex} +\import{topology/topological-space.tex} +\import{topology/separation.tex} +\import{topology/continuous.tex} +\import{topology/basis.tex} +\import{numbers.tex} +\import{function.tex} + + +\section{The canonical topology on $\mathbbR$} + +\begin{definition}\label{topological_basis_reals_eps_ball} + $\topoBasisReals = \{ \epsBall{x}{\epsilon} \mid x \in \reals, \epsilon \in \realsplus\}$. +\end{definition} + +\begin{theorem}\label{reals_as_topo_space} + Suppose $\opens[\reals] = \genOpens{\topoBasisReals}{\reals}$. + Then $\reals$ is a topological space. +\end{theorem} +\begin{proof} + Omitted. +\end{proof}
\ No newline at end of file diff --git a/library/topology/urysohn2.tex b/library/topology/urysohn2.tex index dbcfc53..a3f3ea4 100644 --- a/library/topology/urysohn2.tex +++ b/library/topology/urysohn2.tex @@ -12,32 +12,11 @@ \import{set/powerset.tex} \import{set/fixpoint.tex} \import{set/product.tex} +\import{topology/real-topological-space.tex} \section{Urysohns Lemma} -\begin{definition}\label{minimum} - $\min{X} = \{x \in X \mid \forall y \in X. x \leq y \}$. -\end{definition} - - -\begin{definition}\label{maximum} - $\max{X} = \{x \in X \mid \forall y \in X. x \geq y \}$. -\end{definition} - - -\begin{definition}\label{intervalclosed} - $\intervalclosed{a}{b} = \{x \in \reals \mid a \leq x \leq b\}$. -\end{definition} - - -\begin{definition}\label{intervalopen} - $\intervalopen{a}{b} = \{ x \in \reals \mid a < x < b\}$. -\end{definition} - -\begin{definition}\label{one_to_n_set} - $\seq{m}{n} = \{x \in \naturals \mid m \leq x \leq n\}$. -\end{definition} \begin{definition}\label{sequence} @@ -89,26 +68,6 @@ \end{definition} -\begin{axiom}\label{abs_behavior1} - If $x \geq \zero$ then $\abs{x} = x$. -\end{axiom} - -\begin{axiom}\label{abs_behavior2} - If $x < \zero$ then $\abs{x} = \neg{x}$. -\end{axiom} - -\begin{definition}\label{realsminus} - $\realsminus = \{r \in \reals \mid r < \zero\}$. -\end{definition} - -\begin{definition}\label{realsplus} - $\realsplus = \reals \setminus \realsminus$. -\end{definition} - -\begin{definition}\label{epsilon_ball} - $\epsBall{x}{\epsilon} = \intervalopen{x-\epsilon}{x+\epsilon}$. -\end{definition} - \begin{definition}\label{pointwise_convergence} $X$ converge to $x$ iff for all $\epsilon \in \realsplus$ there exist $N \in \dom{X}$ such that for all $n \in \dom{X}$ such that $n > N$ we have $\at{X}{n} \in \epsBall{x}{\epsilon}$. \end{definition} @@ -120,10 +79,61 @@ Then $X$ is a sequence. \end{proposition} -\begin{definition}\label{higher_urysohn_chain} +\begin{definition}\label{lifted_urysohn_chain} $U$ is a lifted urysohnchain of $X$ iff $U$ is a sequence and $\dom{U} = \naturals$ and for all $n \in \dom{U}$ we have $\at{U}{n}$ is a urysohnchain of $X$ and $\at{U}{\suc{n}}$ is a minimal finer extention of $\at{U}{n}$ in $X$. \end{definition} +\begin{definition}\label{normal_ordered_urysohnchain} + $U$ is normal ordered iff there exist $n \in \naturals$ such that $\dom{U} = \seq{\zero}{n}$. +\end{definition} + +\begin{definition}\label{bijection_of_urysohnchains} + $f$ is consistent on $X$ to $Y$ iff $f$ is a bijection from $\dom{X}$ to $\dom{Y}$ and for all $n,m \in \dom{X}$ such that $n < m$ we have $f(n) < f(m)$. +\end{definition} + +\begin{proposition}\label{naturals_in_transitive} + $\naturals$ is a \in-transitive set. +\end{proposition} + +\begin{proposition}\label{naturals_elem_in_transitive} + If $n \in \naturals$ then $n$ is \in-transitive and every element of $n$ is \in-transitive. + %If $n$ is a natural number then $n$ is \in-transitive and every element of $n$ is \in-transitive. + +\end{proposition} + +\begin{proposition}\label{seq_zero_to_n_isomorph_to_n} + For all $n \in \naturals$ we have $\seq{\zero}{n}$ has cardinality $\suc{n}$. +\end{proposition} +\begin{proof} [Proof by \in-induction on $n$] + Assume $n \in \naturals$. + %Assume $n$ is a natural number. + %We show that $\seq{\zero}{\zero}$ has cardinality $1$. + %\begin{subproof} + % It suffices to show that $1 = \seq{\zero}{\zero}$. + % Follows by set extensionality. + %\end{subproof} + %For all $n \in \naturals$ we have either $n = \zero$ or there exist $m \in \naturals$ such that $n = \suc{m}$. + %For all $n \in \naturals$ we have either $n = \zero$ or $\zero \in n$. + %We show that if $\seq{\zero}{n}$ has cardinality $\suc{n}$ then $\seq{\zero}{\suc{n}}$ has cardinality $\suc{\suc{n}}$. + %\begin{subproof} + % Omitted. + %\end{subproof} +\end{proof} + +\begin{proposition}\label{existence_normal_ordered_urysohn} + Let $X$ be a urysohn space. + Suppose $U$ is a urysohnchain of $X$. + Suppose $\dom{U}$ is finite. + Then there exist $V,f$ such that $V$ is a urysohnchain of $X$ and $f$ is consistent on $X$ to $Y$ and $V$ is normal ordered. +\end{proposition} +\begin{proof} + Take $k$ such that $\dom{U}$ has cardinality $k$ by \cref{ran_converse,cardinality,finite}. + There exist $F$ such that $F$ is a bijection from $\seq{\zero}{k}$ to $\dom{U}$. + + +\end{proof} + + \begin{definition}\label{staircase} $f$ is a staircase function adapted to $U$ in $X$ iff $U$ is a urysohnchain of $X$ and for all $x,n,m,k$ such that $k = \max{\dom{U}}$ and $n,m \in \dom{U}$ and $n$ follows $m$ in $\dom{U}$ and $x \in (\at{U}{m} \setminus \at{U}{n})$ we have $f(x)= \rfrac{m}{k}$. \end{definition} @@ -136,9 +146,6 @@ - - - \begin{theorem}\label{urysohnsetinbeetween} Let $X$ be a urysohn space. Suppose $A,B \in \closeds{X}$. @@ -159,9 +166,9 @@ There exist $U$ such that $U$ is a sequence and $\dom{U} = \naturals$ and $\at{U}{\zero} = U_0$ and for all $n \in \dom{U}$ we have $\at{U}{n}$ is a urysohnchain of $X$ and $\at{U}{\suc{n}}$ is a minimal finer extention of $\at{U}{n}$ in $X$. \end{theorem} \begin{proof} - $U_0$ is a urysohnchain of $X$. - It suffices to show that for all $V$ such that $V$ is a urysohnchain of $X$ there exist $V'$ such that $V'$ is a urysohnchain of $X$ and $V'$ is a minimal finer extention of $V$ in $X$. - + %$U_0$ is a urysohnchain of $X$. + %It suffices to show that for all $V$ such that $V$ is a urysohnchain of $X$ there exist $V'$ such that $V'$ is a urysohnchain of $X$ and $V'$ is a minimal finer extention of $V$ in $X$. + Omitted. \end{proof} @@ -246,6 +253,9 @@ \begin{subproof} Follows by \cref{chain_of_subsets,urysohnchain,induction_on_urysohnchains}. \end{subproof} + Take $U$ such that $U$ is a lifted urysohnchain of $X$ and $\at{U}{\zero} = U_0$. + + |