Singular equivalences of Morita type with level, Gorenstein algebras, and universal deformation rings

Abstract

Let $\mathbf{k}$ be a field of arbitrary characteristic, let $\Lambda$ be a finite dimensional $\mathbf{k}$-algebra, and let $V$ be an indecomposable finitely generated non-projective Gorenstein-projective left $\Lambda$-module whose stable endomorphism ring is isomorphic to $\mathbf{k}$. In this article, we prove that the universal deformation rings $R(\Lambda,V)$ and $R(\Lambda,\Omega_\Lambda V)$ are isomorphic, where $\Omega_\Lambda V$ denotes the first syzygy of $V$ as a left $\Lambda$-module. We also prove the following result. Assume that $\Lambda$ is Gorenstein and that $\Gamma$ is another Gorenstein $\mathbf{k}$-algebra such that there exists $\ell \geq 0$ and a pair of bimodules $({_\Gamma}X_\Lambda, {_\Lambda}Y_\Gamma)$ that induces a singular equivalence of Morita type with level $\ell$ (as introduced by Z. Wang) between $\Lambda$ and $\Gamma$. Then the left $\Gamma$-module $X\otimes_\Lambda V$ is also Gorenstein-projective with stable endomorphism ring isomorphic to $\mathbf{k}$ and the universal deformation ring $R(\Gamma, X\otimes_\Lambda V)$ is isomorphic to $R(\Lambda, V)$.