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14 changes: 7 additions & 7 deletions CoveringSpacesProject/RootsComplexPolynomials.lean
Original file line number Diff line number Diff line change
Expand Up @@ -607,7 +607,7 @@ $w(\omega')=w(ω)$.
\begin{corollary}\label{constpath}
Suppose that $\omega\colon [ a, b ]\to \C$ is a loop and $\omega(t)\in Cstar$
for all $t\in [ a, b ]$.
Suppose that $H\colon [ a, b ]\times [ 0, 1 ]\to \C$ is a homotopy of loops
Suppofse that $H\colon [ a, b ]\times [ 0, 1 ]\to \C$ is a homotopy of loops
from $\omega$ to a constant loop
and $H(t,s)\in Cstar$ for all $(t,s)\in [ a, b ]\times [ 0, 1 ]$. Then
the winding number of $\omega$ is zero
Expand Down Expand Up @@ -637,7 +637,7 @@ $\omega\colon [ 0, 2\pi ]\to X$ is defined by $\omega(t)=\psi(CSexp(it))$.

\begin{lemma}\label{sameImage}
Let $ρ : S^1→ \C$ be a map with $ρ(z)∈ Cstar$ for all $z∈ S^1$.
Let $ω\colon [ 0,2\pi ]→ \C$ be the loop associated with $ρ$.
Let $ω$ be the loop associated with $ρ$.
Then the image of $ω$ is contained in $Cstar$.
\end{lemma}

Expand Down Expand Up @@ -680,7 +680,7 @@ of the constant loop at $f(S^1)\in Cstar$. By Lemma~\ref{constpath} this winding
/-%%

\begin{lemma}\label{S1homotopy}
Let $\psi, \psi'\colon S^1\to \C$ be maps and $H : S^1→ \C$ a homotopy $H : S^1→ \C$ between them
Let $\psi, \psi'\colon S^1\to \C$ be maps and $H : S^1→ \C$ a homotopy between them
whose image lies in $Cstar$. Then the winding numbers of $\psi$ and $\psi'$ are equal.
\end{lemma}
%%-/
Expand Down Expand Up @@ -717,20 +717,20 @@ the image of $\hat f$ contained in $Cstar$. Then the winding $w(\rho)=0$.


\begin{proof}\uses{S1homotopy, constS1}
Define a continuous map $J\colon S^1\times [0,1]\to D^2$ by
Define a continuous map $J\colon S^1\times [ 0,1 ]\to D^2$ by
$(z,t)\mapsto (1-t)z$. Then $\hat f\circ J(z,0)= \rho(z)$ and
$\hat f\circ J(z,1)=\hat f(0)$ for all $z\in S^1$.
This is a homotopy in $Cstar$ from $\rho$ to a constant map of $S^1\to Cstar$.
By Lemma~\ref{S1homotopy} the winding number of $\rho$ is equal to the winding number
of a constant map $S^1\to C\star$.
By Lemma~\ref{constS1}, the winding number of a constant
map $S^1\to \hat f(0)\in Cstar$ is zero.
\end{proof}




Since there is a homotopy $H$ from $\rho$
to a constant map with image in $Cstar$, it follows from Corollary~\ref{S1homotopy}
to a constant map with image in $Cstar$, it follows from Lemma~\ref{S1homotopy}
that the winding number of $\rho$ is zero.
\end{proof}

Expand Down Expand Up @@ -850,7 +850,7 @@ is a map $S^1→ \C$ with image contained in $Cstar$ and with winding number $k
\end{theorem}


\begin{proof}\uses{zkWNk, zkdominates, sameWN}
\begin{proof}\uses{zkWNk, zkdominates,sameWN}
By Lemma~\ref{zkdominates} for $R>{\rm max}(1,\sum_{i=1}^k|\beta_j|)$,
and for any $z\in \C$ with $|z|=R$
$|f(z)-\alpha_0z^k| <|\alpha_0 R^k|$. By Lemma~\ref{sameWN} the maps $\alpha_0*R*CSexp(k t *I)$ and
Expand Down