*Accepted Paper*

**Inserted:** 12 sep 2016

**Last Updated:** 13 feb 2017

**Journal:** Calc. Var. Partial Diff. Equations

**Year:** 2017

**Doi:** 10.1007/s00526-017-1108-x

**Abstract:**

We prove the density of polyhedral partitions in the set of finite Caccioppoli partitions. Precisely, we consider a decomposition $u$ of a bounded Lipschitz set $\Omega\subset{\mathbb R}^n$ into finitely many subsets of finite perimeter, which can be identified with a function in $SBV_{\rm loc}(\Omega;{\cal Z})$ with ${\cal Z}\subset {\mathbb R}^N$ a finite set of parameters. For all $\varepsilon>0$ we prove that such a $u$ is $\varepsilon$-close to a small deformation of a polyhedral decomposition $v_\varepsilon$, in the sense that there is a $C^1$ diffeomorphism $f_\varepsilon:{\mathbb R}^n\to{\mathbb R}^n$ which is $\varepsilon$-close to the identity and such that $u\circ f_\varepsilon-v_\varepsilon$ is $\varepsilon$-small in the strong $BV$ norm. This implies that the energy of $u$ is close to that of $v_\varepsilon$ for a large class of energies defined on partitions. Such types of approximations are very useful in order to simplify computations in the estimates of $\Gamma$-limits.

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