The Tits construction for short $\mathfrak{sl}_2$-super-structures
Gonzalo Gutierrez, Marco Farinati
TL;DR
The paper extends the Tits construction to short and very short $\mathfrak{sl}_2$-structures in the super setting by introducing $\mathfrak{J}$-ternary superalgebras $(\mathfrak{J},\mathcal{M})$, and by developing a functorial replacement for inner derivations via $\mathfrak{B}^s(\mathfrak{J},\mathcal{M})$ and the TAG construction. It proves that short $\sl_2$-Lie superalgebras correspond to such ternary data with explicit bracket formulas, and it constructs the TAG functor as a left adjoint to an extended Tits functor, thereby unifying and generalizing prior non-super and super short constructions (EBCC23, S22). The work gives detailed algebraic identities, adjunction properties, and a suite of examples (including Heisenberg, $\mathrm{osp}(1|2)$, and $\sl_3$ realizations) that illustrate the framework and its capacity to generate new short $\sl_2$-superalgebras from ternary Jordan data. Overall, the results provide a cohesive, functorial mechanism to derive short $\sl_2$-Lie superalgebras from ternary Jordan superstructures, with potential applications in constructing exceptional or otherwise intricate Lie superalgebras from Jordan-like data.
Abstract
In this paper, we generalize the Tits construction for Lie superalgebras such that $\mathfrak{sl}_2$ acts by even derivations and decompose, as $\mathfrak{sl}_2$-module, into a direct sum of copies of the adjoint, the natural and the trivial representations. This construction generalizes the one provided by Elduque et al in \cite{EBCC23}, and it is possible to described the $\mathfrak{sl}_2$-Lie superstructure in terms of $\mathcal{J}$-ternary superalgebras as a super version of the defined by Allison. We extend the Tits-Kantor-Koecher construction and the Tits-Allison-Gao functor that define a short $\mathfrak{sl}_2$-Lie superalgebra from a $\mathcal{J}$-ternary superalgebra $(\mathcal{J},\mathcal{M})$. Our setting includes and generalizes both \cite{EBCC23} and Shang's \cite{S22}.
