arXiv subjects

Justin Fong

Publications and source records attributed to Justin Fong.

3 recordsLinked to original sources

arXiv2025

The $F$-pure threshold of a Schubert cycle

The $F$-pure threshold is the characteristic $p$ counter part of the log canonical threshold in characteristic zero. It is a numerical invariant associated to the singularities of a variety, hence computing its value is important. We give a closed formula for the $F$-pure threshold of the irrelevant maximal ideal of Schubert cycles, which are the homogeneous coordinate rings of Schubert subvarieties of a Grassmannian. The main point of the computation is to give an explicit formula for the $a$-invariant of a Schubert cycle. The derivation of both formulas is made possible through the combinatorics of the underlying poset of these rings.

math.AC↗

arXiv2024

$F$-pure threshold for the symmetric determinantal ring

We give a value for the $F$-pure threshold at the maximal homogeneous ideal $\mathfrak{m}$ of the symmetric determinantal ring over a field of prime characteristic. The answer is characteristic independent, so we immediately get the log canonical threshold in characteristic zero as well.

math.AC↗

arXiv2023

Computing the $F$-pure Threshold of Flag Varieties

We compute the $F$-pure threshold of the natural cone over flag varieties in characteristic $p>0$. Our calculations are mainly focused on flag varieties that are arithmetically Gorenstein, but we offer some results in the non-Gorenstein case. Our goal is to determine the $a$-invariant of the cone. As a result, the $F$-pure thresholds we find are independent of the characteristic $p$, hence one immediately gets the value of the log canonical threshold of flags in characteristic 0 as well.

math.AG↗