A short exposition of the Patak-Tancer theorem on non-embeddability of $k$-complexes in $2k$-manifolds

In 2019 P. Patak and M. Tancer obtained the following higher-dimensional generalization of the Heawood inequality on embeddings of graphs into surfaces. We expose this result in a short well-structured way accessible to non-specialists in the field. Let $Delta_n^k$ be the union of $k$-dimensional faces of the $n$-dimensional simplex. Theorem. (a) If $Delta_n^k$ PL embeds into the connected sum of $g$ copies of the Cartesian product $S^ktimes S^k$ of two $k$-dimensional spheres, then $ggedfrac{n-2k}{k+2}$. (b) If $Delta_n^k$ PL embeds into a closed $(k-1)$-connected PL $2k$-manifold $M$, then $(-1)^k(chi(M)-2)gedfrac{n-2k}{k+1}$.