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Errata fixed in section 19 (Principal Bundles) #4

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12 changes: 6 additions & 6 deletions ga/19principal.tex
Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,7 @@ \subsection{Lie group actions on a manifold}
\ei
satisfying
\ben[label=\roman*)]
\item $\forall \, p \in M :\ p\racts g = p$;
\item $\forall \, p \in M :\ p\racts e = p$;
\item $\forall \, g_1,g_2\in G : \forall \, p\in M : \ p \racts (g_1\bullet g_2) = (p \racts g_1) \racts g_2$.
\een
\ed
Expand Down Expand Up @@ -197,7 +197,7 @@ \subsection{Lie group actions on a manifold}
A left $G$-action $\lacts\cl G\times M\to M$ is said to be
\ben[label=\roman*)]
\item \emph{free} if for all $p\in M$, we have $S_p=\{e\}$;
\item \emph{transitive} if for all $p,q\in M$, there exists $g\in G$ such that $p=g\lacts p$.
\item \emph{transitive} if for all $p,q\in M$, there exists $g\in G$ such that $q=g\lacts p$.
\een
\ed

Expand Down Expand Up @@ -229,7 +229,7 @@ \subsection{Lie group actions on a manifold}
\bp
If $\lacts\cl G \times M \to M$ is a free action, then
\bse
\forall \, p \in G :\ G_p \cong_{\mathrm{diff}} G.
\forall \, p \in M :\ G_p \cong_{\mathrm{diff}} G.
\ese
\ep

Expand Down Expand Up @@ -281,11 +281,11 @@ \subsection{Principal fibre bundles}
\ben[label=\alph*)]
\item Let $M$ be a smooth manifold. Consider the space
\bse
L_pM := \{(e_1,\ldots,e_{\dim M})\mid e_1,\ldots,e_{\dim M} \text{ is a basis of }T_pM\} \cong_{\mathrm{vec}} \GL(\dim M,\R).
L_pM := \{(e_1,\ldots,e_{\dim M})\mid e_1,\ldots,e_{\dim M} \text{ is a basis of }T_pM\} \cong_{\mathrm{LG}} \GL(\dim M,\R).
\ese
We know from linear algebra that the bases of a vector space are related to each other by invertible linear transformations. Hence, we have
\bse
L_pM \cong_{\mathrm{vec}} \GL(\dim M,\R).
L_pM \cong_{\mathrm{LG}} \GL(\dim M,\R).
\ese
We define the frame bundle of $M$ as
\bse
Expand All @@ -294,7 +294,7 @@ \subsection{Principal fibre bundles}
with the obvious projection map $\pi\cl LM \to M$ sending each basis $(e_1,\ldots,e_{\dim M})$ to the unique point $p\in M$ such that $(e_1,\ldots,e_{\dim M})$ is a basis of $T_pM$.
By proceeding similarly to the case of the tangent bundle, we can equip $LM$ with a smooth structure inherited from that of $M$. We then find
\bse
\dim LM = \dim M + \dim T_pM = \dim M + (\dim M)^2.
\dim LM = \dim M + \dim L_pM = \dim M + (\dim M)^2.
\ese
\item We would now like to make $LM \xrightarrow{\,\pi\,}M$ into a principal $\GL(\dim M,\R)$-bundle. We define a right $\GL(\dim M,\R)$-action on $LM$ by
\bse
Expand Down