Uniformly convex Banach space (source code)

= Uniformly convex Banach space
{wiki=Uniformly_convex_space}

A Banach space $X$ is uniformly convex when, for every $\varepsilon>0$, some $\delta>0$ satisfies
$$
\lVert x\rVert,\lVert y\rVert\leq1,
\quad \lVert x-y\rVert\geq\varepsilon
\quad\Longrightarrow\quad
\left\lVert\frac{x+y}{2}\right\rVert\leq1-\delta.
$$