<p>In this paper, we investigate the homological properties of <i>n</i>-coherent rings and extend several classical results to this framework. An <i>n</i>-coherent ring, for <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(n \in \mathbb {N}^* \cup \{\infty \}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">N</mi> </mrow> <mo>∗</mo> </msup> <mo>∪</mo> <mrow> <mo stretchy="false">{</mo> <mi>∞</mi> <mo stretchy="false">}</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, is defined by the property that every finitely generated submodule of a free module with projective dimension at most <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(n-1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>-</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> is finitely presented. We introduce the concepts of <i>n</i>-flat and <i>n</i>-FP-injective modules, exploring their implications for the structure of <i>n</i>-coherent rings. Through the development of <i>n</i>-flat dimensions and <i>n</i>-weak global dimensions, we provide new characterizations of <i>n</i>-semihereditary and <i>n</i>-von Neumann regular rings. Additionally, we investigate quasi-perfect rings and confirm that weak <i>n</i>-von Neumann regular rings are quasi-perfect, thereby answering an open question posed by Mahdou. These results broaden the understanding of coherence and flatness in commutative algebra, linking these properties to projectivity and injectivity in novel ways.</p>

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Homological characterizations of n-coherent rings

  • Younes El Haddaoui,
  • Hwankoo Kim,
  • Najib Mahdou

摘要

In this paper, we investigate the homological properties of n-coherent rings and extend several classical results to this framework. An n-coherent ring, for \(n \in \mathbb {N}^* \cup \{\infty \}\) n N { } , is defined by the property that every finitely generated submodule of a free module with projective dimension at most \(n-1\) n - 1 is finitely presented. We introduce the concepts of n-flat and n-FP-injective modules, exploring their implications for the structure of n-coherent rings. Through the development of n-flat dimensions and n-weak global dimensions, we provide new characterizations of n-semihereditary and n-von Neumann regular rings. Additionally, we investigate quasi-perfect rings and confirm that weak n-von Neumann regular rings are quasi-perfect, thereby answering an open question posed by Mahdou. These results broaden the understanding of coherence and flatness in commutative algebra, linking these properties to projectivity and injectivity in novel ways.