The presentation conjecture for the even subalgebra of the TAMA

From papers

Let U(so(n))U(\mathfrak{so}(n)) be the universal enveloping algebra, and let O0\mathfrak{O}_{\overline{0}} denote the even subalgebra of the TAMA. For a sequence A=(a1,a2,a3,a4)A=(a_1,a_2,a_3,a_4) of four distinct indices, write

XA=Xa1a2Xa3a4+Xa1a3Xa4a2+Xa1a4Xa2a3,X_A=X_{a_1a_2}X_{a_3a_4}+X_{a_1a_3}X_{a_4a_2}+X_{a_1a_4}X_{a_2a_3},

where Xij=EijEjiU(so(n))X_{ij}=E_{ij}-E_{ji}\in U(\mathfrak{so}(n)). Let II be the ideal in the exact sequence

0IU(so(n))O00.0\to I\to U(\mathfrak{so}(n))\to\mathfrak{O}_{\overline{0}}\to0.

For sequences A=(a1,a2,a3,a4)A=(a_1,a_2,a_3,a_4) and B=(b1,b2,b3,b4)B=(b_1,b_2,b_3,b_4) of four distinct indices, and with T\mathcal{T} defined as in the source, the presentation conjecture for the even subalgebra of the TAMA. The ideal II is generated by the elements

σTσ(XAXB+(a,b)ABXA(a,b)XB(a,b))12δA,B,\sum_{\sigma\in\mathcal{T}}\sigma\left(X_AX_B+\sum_{(a,b)\subset A\cap B}X_{A\setminus(a,b)}X_{B\setminus(a,b)}\right)-12\delta_{A,B},

and consequently

O0U(so(n))/σTσ(XAXB+(a,b)ABXA(a,b)XB(a,b))12δA,B.\mathfrak{O}_{\overline{0}}\cong U(\mathfrak{so}(n))\bigg/\left\langle\sum_{\sigma\in\mathcal{T}}\sigma\left(X_AX_B+\sum_{(a,b)\subset A\cap B}X_{A\setminus(a,b)}X_{B\setminus(a,b)}\right)-12\delta_{A,B}\right\rangle.

This conjecture proposes an explicit presentation of the even TAMA in terms of generators and relations; the supplied text gives no evidence that the presentation has been proved or disproved.

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Sources & referencesView supporting material

Primary source

Kieran Calvert, Marcelo De Martino and Roy Oste, “On angular momentum algebras and their relations”, arXiv:2508.18454 (2025).

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