diff --git a/2021_Algebra_I.tex b/2021_Algebra_I.tex index c221530..6519960 100644 --- a/2021_Algebra_I.tex +++ b/2021_Algebra_I.tex @@ -1844,9 +1844,9 @@ Let $R = \mathfrak{k}[X_1,\ldots,X_n]$ and $I \subseteq R$ an ideal. \begin{corollary}\label{codimintersection} Let $A$ and $B$ be irreducible subsets of $\mathfrak{k}^n$. If $C$ is an irreducible component of $A \cap B$, then $\codim(C, \mathfrak{k}^n) \le \codim(A, \mathfrak{k}^n) + \codim(B, \mathfrak{k}^n)$. \end{corollary} -\begin{dremark} +\begin{remark}+ Equivalently, $\dim(C) \ge \dim(A) + \dim(B)-n$. -\end{dremark} +\end{remark} \begin{proof} Let $X = A \times B \subseteq \mathfrak{k}^{2n}$, where we use $(X_1,\ldots,X_n,Y_1,\ldots,Y_n)$ as coordinates of $\mathfrak{k}^{2n}$. Let $\Delta \coloneqq \{(x_1,\ldots,x_n,x_1,\ldots,x_n) | x \in \mathfrak{k}^n\} $ be the diagonal in $\mathfrak{k}^n \times \mathfrak{k}^n$.