Permutohedral complex and complements of diagonal subspace arrangements

The complement of an arrangement of diagonal subspaces $x_{i_1} = \cdots = x_{i_k}$ in the real space is defined by a simplicial complex $\mathcal K$. In this paper, we prove that the complement of a diagonal subspace arrangement is homotopy equivalent to a subcomplex $Perm(\mathcal K)$ of faces of the permutohedron. The product in the cohomology ring of a diagonal arrangement complement is then described via the cellular approximation of the diagonal map in the permutohedron constructed by Saneblidze and Umble. We consider the projection from the permutohedron to the cube and prove that the Saneblidze–Umble diagonal maps to the diagonal constructed by Cai for the description of the product in the cohomology of a real moment-angle complex.