<p>Let <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathscr{R}_{\alpha}^{\Lambda}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msubsup> <mrow> <mi mathvariant="script">R</mi> </mrow> <mrow> <mi>α</mi> </mrow> <mrow> <mi>Λ</mi> </mrow> </msubsup> </math></EquationSource> </InlineEquation> be the cyclotomic Khovanov-Lauda-Rouquier (KLR) algebra associated with a symmetrizable Kac-Moody Lie algebra <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\frak{g}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="fraktur">g</mi> </mrow> </math></EquationSource> </InlineEquation>, polynomials {<i>Q</i><sub><i>ij</i></sub>(<i>u, v</i>)}<sub><i>i,j</i>∈<i>I</i></sub> and <i>α</i> in the positive root lattice. Shan et al. (2017) have shown that, when the ground field <i>K</i> has characteristic 0, the degree <i>d</i> component of the cocenter <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\text{Tr}(\mathscr{R}_{\alpha}^{\Lambda})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Tr</mtext> <mo stretchy="false">(</mo> <msubsup> <mrow> <mi mathvariant="script">R</mi> </mrow> <mrow> <mi>α</mi> </mrow> <mrow> <mi>Λ</mi> </mrow> </msubsup> <mo stretchy="false">)</mo> </math></EquationSource> </InlineEquation> is nonzero only if 0 ⩽ <i>d</i> ⩽ <i>d</i><sub>Λ<i>α</i></sub>, and the dimension of the degree 0 component <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\text{Tr}(\mathscr{R}_{\alpha}^{\Lambda})_{0}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Tr</mtext> <mo stretchy="false">(</mo> <msubsup> <mrow> <mi mathvariant="script">R</mi> </mrow> <mrow> <mi>α</mi> </mrow> <mrow> <mi>Λ</mi> </mrow> </msubsup> <msub> <mo stretchy="false">)</mo> <mrow> <mn>0</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> is always equal to dim <i>V</i>(Λ)<sub>Λ−<i>α</i></sub>, where <i>V</i>(Λ) is the integrable highest weight <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(U({\frak{g}})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi>U</mi> <mo stretchy="false">(</mo> <mrow> <mrow> <mi mathvariant="fraktur">g</mi> </mrow> </mrow> <mo stretchy="false">)</mo> </math></EquationSource> </InlineEquation>-module with the highest weight Λ. In this paper, we show that these results hold for an arbitrary ground field <i>K</i>, arbitrary <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\frak{g}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="fraktur">g</mi> </mrow> </math></EquationSource> </InlineEquation> and arbitrary polynomials {<i>Q</i><sub><i>ij</i></sub>(<i>u,v</i>)}<sub><i>i,j</i>∈<i>I</i></sub>. We prove these results by generalizing our earlier results (Theorem 1.3 of Hu and Shi (2023)) on the <i>K</i>-linear generators of <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\text{Tr}(\mathscr{R}_{\alpha}^{\Lambda})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Tr</mtext> <mo stretchy="false">(</mo> <msubsup> <mrow> <mi mathvariant="script">R</mi> </mrow> <mrow> <mi>α</mi> </mrow> <mrow> <mi>Λ</mi> </mrow> </msubsup> <mo stretchy="false">)</mo> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\text{Tr}(\mathscr{R}_{\alpha}^{\Lambda})_{0}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Tr</mtext> <mo stretchy="false">(</mo> <msubsup> <mrow> <mi mathvariant="script">R</mi> </mrow> <mrow> <mi>α</mi> </mrow> <mrow> <mi>Λ</mi> </mrow> </msubsup> <msub> <mo stretchy="false">)</mo> <mrow> <mn>0</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\text{Tr}({\mathscr{R}}_{\alpha}^{\Lambda})_{d_{\Lambda, \alpha}}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Tr</mtext> <mo stretchy="false">(</mo> <msubsup> <mrow> <mrow> <mi mathvariant="script">R</mi> </mrow> </mrow> <mrow> <mi>α</mi> </mrow> <mrow> <mi mathvariant="normal">Λ</mi> </mrow> </msubsup> <msub> <mo stretchy="false">)</mo> <mrow> <msub> <mi>d</mi> <mrow> <mi mathvariant="normal">Λ</mi> <mo>,</mo> <mi>α</mi> </mrow> </msub> </mrow> </msub> </math></EquationSource> </InlineEquation> to arbitrary ground field <i>K</i>, and we give a basis for <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\text{Tr}({\mathscr{R}}_{\alpha}^{\Lambda})_{0}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mtext>Tr</mtext> <mo stretchy="false">(</mo> <msubsup> <mrow> <mrow> <mi mathvariant="script">R</mi> </mrow> </mrow> <mrow> <mi>α</mi> </mrow> <mrow> <mi mathvariant="normal">Λ</mi> </mrow> </msubsup> <msub> <mo stretchy="false">)</mo> <mrow> <mn>0</mn> </mrow> </msub> </math></EquationSource> </InlineEquation>.</p>

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On the maximal and minimal degree components of the cocenter of the cyclotomic KLR algebra

  • Jun Hu,
  • Lei Shi

摘要

Let \(\mathscr{R}_{\alpha}^{\Lambda}\) R α Λ be the cyclotomic Khovanov-Lauda-Rouquier (KLR) algebra associated with a symmetrizable Kac-Moody Lie algebra \(\frak{g}\) g , polynomials {Qij(u, v)}i,jI and α in the positive root lattice. Shan et al. (2017) have shown that, when the ground field K has characteristic 0, the degree d component of the cocenter \(\text{Tr}(\mathscr{R}_{\alpha}^{\Lambda})\) Tr ( R α Λ ) is nonzero only if 0 ⩽ ddΛα, and the dimension of the degree 0 component \(\text{Tr}(\mathscr{R}_{\alpha}^{\Lambda})_{0}\) Tr ( R α Λ ) 0 is always equal to dim V(Λ)Λ−α, where V(Λ) is the integrable highest weight \(U({\frak{g}})\) U ( g ) -module with the highest weight Λ. In this paper, we show that these results hold for an arbitrary ground field K, arbitrary \(\frak{g}\) g and arbitrary polynomials {Qij(u,v)}i,jI. We prove these results by generalizing our earlier results (Theorem 1.3 of Hu and Shi (2023)) on the K-linear generators of \(\text{Tr}(\mathscr{R}_{\alpha}^{\Lambda})\) Tr ( R α Λ ) , \(\text{Tr}(\mathscr{R}_{\alpha}^{\Lambda})_{0}\) Tr ( R α Λ ) 0 and \(\text{Tr}({\mathscr{R}}_{\alpha}^{\Lambda})_{d_{\Lambda, \alpha}}\) Tr ( R α Λ ) d Λ , α to arbitrary ground field K, and we give a basis for \(\text{Tr}({\mathscr{R}}_{\alpha}^{\Lambda})_{0}\) Tr ( R α Λ ) 0 .