Congruence modules and Wiles defects of determinantal rings of maximal minors

Abstract

Let $O$ be a discrete valuation ring and $A := O[X_{m \times n}]/I_{m}(X)$ the determinantal ring of maximal minors. We consider algebra maps $\lambda \colon A \to O$, which is tantamount to choosing rank-deficient matrices $a \in O^{m \times n}$. Following Iyengar--Khare--Manning, we compute the congruence module and the Wiles defect of $A$ at $\lambda$, expressing them in terms of the $(m - 1)$-sized minors of $a$.