<p>In this paper, we study tilting and cotilting subcategories of the category of representations of a quiver. Let <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\cal{M}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">M</mi> </mrow> </math></EquationSource> </InlineEquation> be an abelian category, <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\cal{Q}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">Q</mi> </mrow> </math></EquationSource> </InlineEquation> be a rooted quiver, and <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\text{Rep}(\cal{Q,M})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Rep</mtext> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="script">Q</mi> <mo class="MJX-tex-caligraphic" mathvariant="script">,</mo> <mi mathvariant="script">M</mi> </mrow> <mo class="MJX-tex-caligraphic" mathvariant="script" stretchy="false">)</mo> </math></EquationSource> </InlineEquation> be the category of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\cal{M}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">M</mi> </mrow> </math></EquationSource> </InlineEquation>-valued representations of <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\cal{Q}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">Q</mi> </mrow> </math></EquationSource> </InlineEquation>. By using some recent results about cotorsion torsion triples (resp. torsion cotorssion triples), under certain assumptions, we show that if <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\cal{T}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">T</mi> </mrow> </math></EquationSource> </InlineEquation> is a 1-tilting (resp. 1-cotilting) subcategory of <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\cal{M}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">M</mi> </mrow> </math></EquationSource> </InlineEquation>, then the monomorphism category <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\Phi(\cal{T})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi mathvariant="normal">Φ</mi> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="script">T</mi> </mrow> <mo class="MJX-tex-caligraphic" mathvariant="script" stretchy="false">)</mo> </math></EquationSource> </InlineEquation> (resp. the epimorphism category <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\Psi(\cal{T})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi mathvariant="normal">Ψ</mi> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="script">T</mi> </mrow> <mo class="MJX-tex-caligraphic" mathvariant="script" stretchy="false">)</mo> </math></EquationSource> </InlineEquation>) is a 1-tilting (resp. 1-cotilting) subcategory of <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\text{Rep}(\cal{Q,M})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Rep</mtext> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="script">Q</mi> <mo class="MJX-tex-caligraphic" mathvariant="script">,</mo> <mi mathvariant="script">M</mi> </mrow> <mo class="MJX-tex-caligraphic" mathvariant="script" stretchy="false">)</mo> </math></EquationSource> </InlineEquation>. Then, we study another types of induced subcategories in <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\text{Rep}(\cal{Q,M})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Rep</mtext> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="script">Q</mi> <mo class="MJX-tex-caligraphic" mathvariant="script">,</mo> <mi mathvariant="script">M</mi> </mrow> <mo class="MJX-tex-caligraphic" mathvariant="script" stretchy="false">)</mo> </math></EquationSource> </InlineEquation> and, by using nice descriptions of monomorphism and epimorphism categories, show that if <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\cal{T}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">T</mi> </mrow> </math></EquationSource> </InlineEquation> is a tilting (resp. cotilting) subcategory of <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\cal{M}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">M</mi> </mrow> </math></EquationSource> </InlineEquation>, then the epimorphism category <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(\Psi(\cal{T})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi mathvariant="normal">Ψ</mi> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="script">T</mi> </mrow> <mo class="MJX-tex-caligraphic" mathvariant="script" stretchy="false">)</mo> </math></EquationSource> </InlineEquation> (resp. the monomorphism category <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\(\Phi(\cal{T})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi mathvariant="normal">Φ</mi> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="script">T</mi> </mrow> <mo class="MJX-tex-caligraphic" mathvariant="script" stretchy="false">)</mo> </math></EquationSource> </InlineEquation>) is a tilting (resp. cotilting) subcategory of <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(\text{Rep}(\cal{Q,M})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Rep</mtext> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="script">Q</mi> <mo class="MJX-tex-caligraphic" mathvariant="script">,</mo> <mi mathvariant="script">M</mi> </mrow> <mo class="MJX-tex-caligraphic" mathvariant="script" stretchy="false">)</mo> </math></EquationSource> </InlineEquation> for every finite acyclic quiver <InlineEquation ID="IEq17"> <EquationSource Format="TEX">\(\cal{Q}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">Q</mi> </mrow> </math></EquationSource> </InlineEquation>. This result is a generalization of a lemma due to Zhang (2011) about induced cotilting modules and some recent results due to Bauer et al. (2020). We finally extend Zhang’s reciprocity of the monomorphism operator and the left perpendicular operator for cotilting modules to cotilting subcategories. The results give us a systematic method to create new tilting and cotilting subcategories.</p>

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Tilting and cotilting subcategories in categories of quiver representations

  • Mohammad Hossein Keshavarz,
  • Guodong Zhou

摘要

In this paper, we study tilting and cotilting subcategories of the category of representations of a quiver. Let \(\cal{M}\) M be an abelian category, \(\cal{Q}\) Q be a rooted quiver, and \(\text{Rep}(\cal{Q,M})\) Rep ( Q , M ) be the category of \(\cal{M}\) M -valued representations of \(\cal{Q}\) Q . By using some recent results about cotorsion torsion triples (resp. torsion cotorssion triples), under certain assumptions, we show that if \(\cal{T}\) T is a 1-tilting (resp. 1-cotilting) subcategory of \(\cal{M}\) M , then the monomorphism category \(\Phi(\cal{T})\) Φ ( T ) (resp. the epimorphism category \(\Psi(\cal{T})\) Ψ ( T ) ) is a 1-tilting (resp. 1-cotilting) subcategory of \(\text{Rep}(\cal{Q,M})\) Rep ( Q , M ) . Then, we study another types of induced subcategories in \(\text{Rep}(\cal{Q,M})\) Rep ( Q , M ) and, by using nice descriptions of monomorphism and epimorphism categories, show that if \(\cal{T}\) T is a tilting (resp. cotilting) subcategory of \(\cal{M}\) M , then the epimorphism category \(\Psi(\cal{T})\) Ψ ( T ) (resp. the monomorphism category \(\Phi(\cal{T})\) Φ ( T ) ) is a tilting (resp. cotilting) subcategory of \(\text{Rep}(\cal{Q,M})\) Rep ( Q , M ) for every finite acyclic quiver \(\cal{Q}\) Q . This result is a generalization of a lemma due to Zhang (2011) about induced cotilting modules and some recent results due to Bauer et al. (2020). We finally extend Zhang’s reciprocity of the monomorphism operator and the left perpendicular operator for cotilting modules to cotilting subcategories. The results give us a systematic method to create new tilting and cotilting subcategories.