- Commit
- d0aecccb60a0dc077bb08b750edba81cab02c2b9
- Parent
- 8e31e9df7dc7e009f77e89645ba865ff4df6aba9
- Author
- Pablo <pablo-escobar@riseup.net>
- Date
Fixed multiple typos
Source code for my notes on representations of semisimple Lie algebras and Olivier Mathieu's classification of simple weight modules
Fixed multiple typos
1 file changed, 9 insertions, 9 deletions
Status | File Name | N° Changes | Insertions | Deletions |
Modified | sections/introduction.tex | 18 | 9 | 9 |
diff --git a/sections/introduction.tex b/sections/introduction.tex @@ -21,7 +21,7 @@ called \emph{Lie algebras}, and these will be the focus of these notes. Given a field \(K\), a Lie algebra over \(K\) is a \(K\)-vector space \(\mathfrak{g}\) endowed with an antisymmetric bilinear map \([\, ,] : \mathfrak{g} \times \mathfrak{g} \to \mathfrak{g}\) -- which we call its - \emph{Lie brackets} -- satisfying the Jacobi identity + \emph{Lie bracket} -- satisfying the Jacobi identity \[ [X, [Y, Z]] + [Y, [Z, X]] + [Z, [X, Y]] = 0 \] @@ -31,7 +31,7 @@ called \emph{Lie algebras}, and these will be the focus of these notes. Given two Lie algebras \(\mathfrak{g}\) and \(\mathfrak{h}\) over \(K\), a homomorphism of Lie algebras \(\mathfrak{g} \to \mathfrak{h}\) is a \(K\)-linear map \(f : \mathfrak{g} \to \mathfrak{h}\) which \emph{preserves - brackets} in the sense that + bracket} in the sense that \[ f([X, Y]) = [f(X), f(Y)] \] @@ -48,7 +48,7 @@ associative algebras. \begin{example}\label{ex:inclusion-alg-in-lie-alg} Given an associative \(K\)-algebra \(A\), we can view \(A\) as a Lie algebra - over \(K\) with the Lie brackets given by the commutator \([a, b] = ab - + over \(K\) with the Lie bracket given by the commutator \([a, b] = ab - ba\). In particular, given a \(K\)-vector space \(V\) we may view the \(K\)-algebra \(\operatorname{End}(V)\) as a Lie algebra, which we call \(\mathfrak{gl}(V)\). We may also regard the Lie algebra \(\mathfrak{gl}_n(K) @@ -111,7 +111,7 @@ One specific instance of this last example is\dots the left translation by \(g\). The commutator of invariant fields is invariant, so the space \(\mathfrak{g} = \operatorname{Lie}(G)\) of all invariant vector fields has the structure of a Lie algebra over - \(\mathbb{R}\) with brackets given by the usual commutator of fields. Notice + \(\mathbb{R}\) with bracket given by the usual commutator of fields. Notice that an invariant field \(X\) is completely determined by \(X_1 \in T_1 G\). Hence there is a linear isomorphism \(\mathfrak{g} \isoto T_1 G\). In particular, \(\mathfrak{g}\) is finite-dimensional. @@ -134,7 +134,7 @@ this last construction. f)(h) = f(g^{-1} h)\). The commutator of left invariant derivations is invariant too, so the space \(\operatorname{Lie}(G) = \operatorname{Der}(G)^G\) of invariant derivations in \(K[G]\) has the - structure of a Lie algebra over \(K\) with brackets given by the commutator + structure of a Lie algebra over \(K\) with bracket given by the commutator of derivations. Again, \(\operatorname{Lie}(G)\) is isomorphic to the Zariski tangent space \(T_1 G\), which is finite-dimensional. \end{example} @@ -199,7 +199,7 @@ this last construction. X \right\}, \] - with brackets given by the usual commutator of matrices -- where + with bracket given by the usual commutator of matrices -- where \(\operatorname{Id}_n\) denotes the \(n \times n\) identity matrices. \end{example} @@ -309,7 +309,7 @@ is only natural to define\dots \begin{example} Let \(\mathfrak{g}_1\) and \(\mathfrak{g}_2\) be a Lie algebras over \(K\). Then the space \(\mathfrak{g}_1 \oplus \mathfrak{g}_2\) is a Lie algebra with - brackets + bracket \[ [X_1 + X_2, Y_1 + Y_2] = [X_1, Y_1] + [X_2, Y_2], \] @@ -368,7 +368,7 @@ There is also a natural analogue of quotients. any linear map \(\mathfrak{g} \to \mathfrak{h}\) between Abelian Lie algebras \(\mathfrak{g}\) and \(\mathfrak{h}\) is a homomorphism of Lie algebras. In particular, any linear isomorphism \(\mathfrak{g} \isoto K^n\) -- where - \(K^n\) is endowed with the trivial brackets \([v, w] = 0 \, \forall v, w \in + \(K^n\) is endowed with the trivial bracket \([v, w] = 0 \, \forall v, w \in K^n\) -- is an isomorphism of Lie algebras for Abelian \(\mathfrak{g}\). \end{note} @@ -531,7 +531,7 @@ semisimple and reductive algebras by modding out by certain ideals, known as We have seen in Example~\ref{ex:inclusion-alg-in-lie-alg} that we can pass from associative algebras to Lie algebras using the functor \(\operatorname{Lie} : K\text{-}\mathbf{Alg} \to K\text{-}\mathbf{LieAlg}\) that takes an algebra -\(A\) to the Lie algebra \(A\) with brackets given by commutators. We can also +\(A\) to the Lie algebra \(A\) with bracket given by commutators. We can also go the other direction by embedding a Lie algebra \(\mathfrak{g}\) in an associative algebra, known as \emph{the universal enveloping algebra of \(\mathfrak{g}\)}.