Representations of the Loop mirror BMS-Kac-Moody algebra

arXiv:2611.13025v1 Announce Type: new Abstract: In this paper, we construct a new family of non-weight modules $\Omega(\lambda,\zeta,\alpha,\beta,\gamma,\sigma, h)$ over the loop mirror BMS-Kac-Moody algebra $\mathcal{G}$, which is a Takiff-type extension of the loop mirror Heisenberg--Virasoro algebra. We establish criteria for irreducibility, determine their isomorphism classes, and classify all $\mathcal{G}$-modules that are free of rank one. Moreover, we determine all self-extensions of these modules: for every such module $M$, $\operatorname{Ext}^{1}_{U(\mathcal{G})}(M,M)\cong \mathbb{C}^{6}$, and we construct explicit $1$-cocycles realizing every cohomology class. Every nonsplit self-extension of a simple module is indecomposable of composition length two. Restricting these modules to the loop mirror Heisenberg--Virasoro subalgebra $\mathcal{H}$ yields new $\mathcal{H}$-modules. Among them the $\sigma$-type modules $\Psi(\lambda,\zeta,\sigma,\alpha,\beta,\gamma,h)$ constitute a new family with no counterpart in the non-loop or non-Takiff case. For the degenerate case $\sigma=0$, we establish criteria for irreducibility and isomorphism, and describe certain maximal submodules and their simple quotients. Finally, we construct and classify a new class of tensor product $\mathcal{H}$-modules.

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