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On the higher topological Hochschild homology of $\mathbb{F}_p$ and commutative $\mathbb{F}_p$-group algebras

We extend Torleif Veen's calculation of higher topological Hochschild homology ${\sf THH}^{[n]}_*(\mathbb{F}_p)$ from $n\leq 2p$ to $n\leq 2p+2$ for $p$ odd, and from $n=2$ to $n\leq 3$ for $p=2$. We calculate higher Hochschild homology ${\sf HH}_*^{[n]}(k[x])$ over $k$ for any integral domain $k$, and ${\sf HH}_*^{[n]}(\mathbb{F}_p[x]/x^{p^\ell})$ for all $n>0$. We use this and étale descent to calculate ${\sf HH}_*^{[n]}(\mathbb{F}_p[G])$ for all $n>0$ for any cyclic group $G$, and therefore also for any finitely generated abelian group $G$. We show a splitting result for higher ${\sf THH}$ of commutative $\mathbb{F}_p$-group algebras and use this technique to calculate higher topological Hochschild homology of such group algebras for as large an $n$ as ${\sf THH}^{[n]}_*(\mathbb{F}_p) $ is known for.