<p>Let <i>R</i> be a ring, <i>S</i> a partial groupoid (magma), and let <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\{R_s\}_{s\in S}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mo stretchy="false">{</mo> <msub> <mi>R</mi> <mi>s</mi> </msub> <mo stretchy="false">}</mo> </mrow> <mrow> <mi>s</mi> <mo>∈</mo> <mi>S</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> be a family of additive subgroups of <i>R</i>. Then <i>R</i> is said to be (a strongly) <i>S</i>-graded ring inducing <i>S</i> if <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(R=\bigoplus _{s\in S}R_s\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>R</mi> <mo>=</mo> <msub> <mo>⨁</mo> <mrow> <mi>s</mi> <mo>∈</mo> <mi>S</mi> </mrow> </msub> <msub> <mi>R</mi> <mi>s</mi> </msub> </mrow> </math></EquationSource> </InlineEquation> and: i) <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(R_s R_t\subseteq R_{st}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>R</mi> <mi>s</mi> </msub> <msub> <mi>R</mi> <mi>t</mi> </msub> <mo>⊆</mo> <msub> <mi>R</mi> <mrow> <mi mathvariant="italic">st</mi> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation> <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\((R_s R_t=R_{st})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <msub> <mi>R</mi> <mi>s</mi> </msub> <msub> <mi>R</mi> <mi>t</mi> </msub> <mo>=</mo> <msub> <mi>R</mi> <mrow> <mi mathvariant="italic">st</mi> </mrow> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> whenever <i>st</i> is defined; ii) <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(R_s R_t\ne 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>R</mi> <mi>s</mi> </msub> <msub> <mi>R</mi> <mi>t</mi> </msub> <mo>≠</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> implies the product <i>st</i> is defined. The class of <i>S</i>-graded rings inducing <i>S</i> encompasses all the classes of graded rings. <i>R</i> is said to be pseudo-unitary if, moreover: iii) <i>S</i> is cancellative; iv) for every idempotent element <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(e\in S\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>e</mi> <mo>∈</mo> <mi>S</mi> </mrow> </math></EquationSource> </InlineEquation> the ring <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(R_e\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>R</mi> <mi>e</mi> </msub> </math></EquationSource> </InlineEquation> is with unity <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(1_e;\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mn>1</mn> <mi>e</mi> </msub> <mo>;</mo> </mrow> </math></EquationSource> </InlineEquation> v) for every homogeneous element <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(x\in R,\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>∈</mo> <mi>R</mi> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> that is, <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(x\in \bigcup _{s\in S}R_s,\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>∈</mo> <msub> <mo>⋃</mo> <mrow> <mi>s</mi> <mo>∈</mo> <mi>S</mi> </mrow> </msub> <msub> <mi>R</mi> <mi>s</mi> </msub> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> there exist idempotent elements <i>e</i>,&#xa0; <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(f\in S\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>∈</mo> <mi>S</mi> </mrow> </math></EquationSource> </InlineEquation> such that <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(1_ex=x=x1_f.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mn>1</mn> <mi>e</mi> </msub> <mi>x</mi> <mo>=</mo> <mi>x</mi> <mo>=</mo> <mi>x</mi> <msub> <mn>1</mn> <mi>f</mi> </msub> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> We give a partial answer to a certain Bergman-type question raised by Andrei Kelarev, by answering it in the affirmative for the class of all pseudo-unitary strongly <i>S</i>-graded rings inducing <i>S</i>,&#xa0; with commutative <i>S</i>,&#xa0; and apply the obtained result to address another problem recorded in [Abawajy, J., Kelarev, A., Chowdhury, M.: Power Graphs: A Survey. Electron. J. Graph Theory Appl. <b>1</b>(2), 125–147 (2013)], related to the connectedness of the power graph of the multiplicative semigroup of all homogeneous elements of a graded algebra over a field of characteristic zero.</p>

错误:搜索内容不能为空,请输入英文关键词
错误:关键词超出字数限制,请精简
高级检索

On the Jacobson radical of graded rings and related power graphs

  • Emil Ilić-Georgijević

摘要

Let R be a ring, S a partial groupoid (magma), and let \(\{R_s\}_{s\in S}\) { R s } s S be a family of additive subgroups of R. Then R is said to be (a strongly) S-graded ring inducing S if \(R=\bigoplus _{s\in S}R_s\) R = s S R s and: i) \(R_s R_t\subseteq R_{st}\) R s R t R st \((R_s R_t=R_{st})\) ( R s R t = R st ) whenever st is defined; ii) \(R_s R_t\ne 0\) R s R t 0 implies the product st is defined. The class of S-graded rings inducing S encompasses all the classes of graded rings. R is said to be pseudo-unitary if, moreover: iii) S is cancellative; iv) for every idempotent element \(e\in S\) e S the ring \(R_e\) R e is with unity \(1_e;\) 1 e ; v) for every homogeneous element \(x\in R,\) x R , that is, \(x\in \bigcup _{s\in S}R_s,\) x s S R s , there exist idempotent elements e \(f\in S\) f S such that \(1_ex=x=x1_f.\) 1 e x = x = x 1 f . We give a partial answer to a certain Bergman-type question raised by Andrei Kelarev, by answering it in the affirmative for the class of all pseudo-unitary strongly S-graded rings inducing S,  with commutative S,  and apply the obtained result to address another problem recorded in [Abawajy, J., Kelarev, A., Chowdhury, M.: Power Graphs: A Survey. Electron. J. Graph Theory Appl. 1(2), 125–147 (2013)], related to the connectedness of the power graph of the multiplicative semigroup of all homogeneous elements of a graded algebra over a field of characteristic zero.