On Stability and Denominators of F-pure thresholds in Families of Diagonal Hypersurfaces

Abstract

Given a prime number $p$ and a positive integer $m$, we provide a family of diagonal hypersurfaces $\{ f_n \}_{n = 1}^{\infty}$ in $m$ variables, for which the denominator of $\text{ fpt } (f_{n})$ (in lowest terms) is always $p$ and whose $F$-pure thresholds stabilize after a certain $n$. We also provide another family of diagonal hypersurfaces $\{ g_n \}_{n = 1}^{\infty}$ in $m$ variables, for which the power of $p$ in the denominator of $\text{ fpt } (g_{n})$ (in lowest terms) diverges to $\infty$ as $n \to \infty$. This behavior of the denominator of the $F$-pure thresholds is dependent on the congruence class of $p$ modulo the smallest two exponents of $\{ f_n \}$ and $\{ g_n \}$.