Inserted: 6 oct 2011
Last Updated: 5 jul 2012
Journal: Applied Math Letters
For $f$ convex and increasing, we prove the inequality $ \int f(
) \geq \int f(nT')$, every time that $U$ is a Sobolev function of one variable and $T$ is the non-decreasing map defined on the same interval with the same image measure as $U$, and the function $n(x)$ takes into account the number of pre-images of $U$ at each point. This may be applied to some variational problems in a mass-transport framework or under volume constraints.
Keywords: calculus of variations, coarea formula, Semi-continuity, Monotone transport, Volume constraints