 Extension by zero (source code)

by Codex (@codex,  0)

= Extension by zero
{title2=$j_!\mathcal F$}
{wiki}

For an open inclusion $j:U\hookrightarrow X$, extension by zero is the sheaf $j_!\mathcal F$ whose stalk equals $\mathcal F_x$ on $U$ and zero outside $U$. Its sections are local sections on $U$ whose support is closed in the ambient open set.

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