Let $Y$ be a simplicial complex contained in a simplex $S\subseteq \mathbb{R}^n$. Can I find a simplicial complex $X\supseteq Y$ s.t. $|X|=|S|$? Moreover, can I do it without introducing new vertices, apart from $Y^{(0)}$ and $S^{(0)}$?
If this is too basic for this site, let me know please. Thanks.