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Minor typo fixes
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Signed-off-by: Marcello Seri <[email protected]>
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mseri committed Jan 18, 2021
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2 changes: 1 addition & 1 deletion 5-tensors.tex
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Expand Up @@ -493,7 +493,7 @@ \section{Tensor bundles}
which may be easier to think about in terms of the following diagram
\begin{equation}\nonumber
\begin{tikzcd}[row sep=large, column sep=tiny]
& \frac{\partial}{\partial x^i} \in \cT_0^1(U) \ni (D\phi)_j^i \frac{\partial}{\partial y^j} \arrow[dl, "\varphi_*" description] \arrow[dr, "\psi*" description] & \\
& \frac{\partial}{\partial x^i} \in \cT_0^1(U) \ni (D\phi)_i^j \frac{\partial}{\partial y^j} \arrow[dl, "\varphi_*" description] \arrow[dr, "\psi*" description] & \\
e_i \in \cT_0^1(V) \arrow[rr, "\phi_*" description] & & \cT_0^1(W) \ni \LaTeXunderbrace{\phi_* e_i}_{= (D\phi)_i^j e_j}
\end{tikzcd}
\end{equation}
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15 changes: 8 additions & 7 deletions 6-differentiaforms.tex
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Expand Up @@ -588,16 +588,17 @@ \section{Exterior derivative}
Let $V$ a vector space of dimension $k$.
A symplectic form on $V$ is an element $\omega\in\Lambda^2(V)$ which is non-degenerate in the sense that $\iota_v(\omega) = 0$ if and only if $v=0$.
Cf. Definition~\ref{def:metric}.
A \emph{symplectic manifold} is a smooth manifold $M$ equipped with a closed differential 2-form $\omega$ such tht $\omega_q$ is a symplectic form on $T_q M$ for every $p\in M$.
A \emph{symplectic manifold} is a smooth manifold $M$ equipped with a closed differential 2-form $\omega$ such tht $\omega_q$ is a symplectic form on $T_q M$ for every $q\in M$.
\begin{enumerate}
\item Prove that if a symplectic form exists, then $k=2n$ for some $n\in\N$, i.e., it must be an even number.
\item Let $M$ be a smooth manifold. Define a $1$-form $\eta\in\Omega^1(T^*M)$ on the cotangent bundle of $M$ as
\begin{equation}
\lambda_{(q,p)}(\xi) = p(d\pi_{(q,p)} \xi),
%\lambda_{(q,p)}(\xi) = p(d\pi_{(q,p)} \xi),
\lambda_{(q,p)} = d\pi_{(q,p)}^*p,
\quad
q\in M, \;
p\in T_q^*M, \;
\xi\in T_{(q,p)}(T^*M),
p\in T_q^*M,
%\;\xi\in T_{(q,p)}(T^*M),
\end{equation}
where $\pi:T^*M\to M$ is the projection to the base.
Show that $\omega := d\lambda$ is a symplectic form on $T^* M$, that is, every cotangent bundle is a symplectic manifold.
Expand Down Expand Up @@ -678,7 +679,7 @@ \section{Lie derivative}
\frac{d}{dt}\Big|_{t=0}\varphi_t^* f(x)
&= \lim_{t\to0} \frac{f(\varphi_t(x)) - f(t)}{t} \\
&= \frac{\partial f}{\partial x^i}\Big|_x X^i(x) \\
&= df(X)(x) = L_X f(x).
&= df(X)(x) = \cL_X f(x).
\end{align}

\newthought{Step III}. Let $\omega = dx^i \in \Omega^1(M)$, then
Expand All @@ -690,7 +691,7 @@ \section{Lie derivative}
\end{align}
On the other hand,
\begin{align}
L_X(dx^i)
\cL_X(dx^i)
&= \iota_X(ddx^i) + d(\iota_X dx^i)\\
&= d(\iota_X dx^i) \\
&= dX^i.
Expand All @@ -700,7 +701,7 @@ \section{Lie derivative}
\end{proof}

\begin{remark}
The Lie derivative can be extended on any tensor bundle $T_s^r(M)$ with the following definition.
The Lie derivative can be extended to any tensor bundle $T_s^r(M)$ with the following definition.
This $T\in\cT_r^s(M)$, for any $p\in M$
\begin{equation}
(\cL_X T)_p := \frac{d}{dt}\Big|_{t=0}\left((\varphi_t^X)^* T\right)_p,
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2 changes: 1 addition & 1 deletion 7-integration.tex
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Expand Up @@ -486,7 +486,7 @@ \section{Integrals on manifolds}
\end{enumerate}
\end{exercise}

\begin{corollary}[Of Theorem\ref{thm:gcv}]
\begin{corollary}[Of Theorem~\ref{thm:gcv}]
Let $F:M\to M$ be a diffeomorphism and $\omega\in\Omega^n(M)$ an invariant volume form, that is, $F^*\omega =\omega$.
Then, for all compactly supported smooth functions $f\in C^\infty_0(M)$, the following holds
\begin{equation}
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