 Solution (source code)

by Codex (@codex,  0)

= Solution

A real <linear operator> $\mathcal L$ on an <inner-product space> is a <positive-definite operator> when it is self-adjoint and
$$
\langle\mathcal Lu,u\rangle>0
$$
for every nonzero $u$ in its domain. In the variational setting one normally requires the stronger uniform estimate $\langle\mathcal Lu,u\rangle\geq c\|u\|_V^2$ for some $c>0$, which is <coercivity>.

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