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A 0-dimensional local ring $(R, \mathfrak{m})$ is called a Teter ring, if there exists a local Gorenstein ring $G$ such that $R\simeq G/(0:\mathfrak{m}_G)$. This class of rings was introduced in 1974 by William Teter. It has been shown by Huneke, Vraciu and others that $R$ is a Teter ring if and only if there exists an epimorphism $\varphi: \omega_R\to \mathfrak{m}$. We call $R$ of Teter type, if there exists an epimorphism $\omega_R\to \mbox{tr}(\omega_R)$, and we define the {\em Teter number} of $R$ to be the smallest number $s$ for which there exist $R$-module homomorphisms $\varphi_i: \omega_R\to R$ such that $\mbox{tr}(\omega_R)=\sum_{i=1}^s\varphi_i(\omega_R)$.
Various characterizations of rings of Teter type are given and families of rings of Teter type are presented. We determine the canonical trace of generic determinantal rings and compute its Teter numbers. As an application we determine the canonical trace of a Cohen-Macaulay ring $R$ of codimension two, which is generically Gorenstein. It is shown that if the defining ideal $I$ of $R$ is generated by $n$ elements, then $\mbox{tr}(\omega_R)$ is generated by the (n-2)-minors of the Hilbert-Burch matrix of $I$.
This is joint work with Gasanova, Hibi and Moradi, and with Ficarra, Stamate and Trivedi.
Coming soon...
Let $(R,m)$ be a Noetherian local ring such that $\widehat{R}$ is reduced. We prove that, when $\widehat{R}$ is $S_2$, if there exists a parameter ideal $Q\subseteq R$ such that the first normal Hilbert-coefficient $\overline{e_1}(Q)$ vanishes, then $R$ is regular and $\nu(m/Q)\leq 1$. This leads to an affirmative answer to a problem raised by Goto-Hong-Mandal. We also give a new proof of the non-negativity of the first normal Hilbert-coefficient (which also shows the non-negativity of the first tight Hilbert-coefficient in positive characteristic).
This is joint work with Pham Hung Quy.
Coming soon...
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