English

Minkowski difference weight formulas

Representation Theory 2024-09-20 v1

Abstract

Fix any complex Kac-Moody Lie algebra g\mathfrak{g}, and Cartan subalgebra hg\mathfrak{h}\subset \mathfrak{g}. We study arbitrary highest weight g\mathfrak{g}-modules VV (with any highest weight λh\lambda\in \mathfrak{h}^*, and let L(λ)L(\lambda) be the corresponding simple highest weight g\mathfrak{g}-module), and write their weight-sets wtV\mathrm{wt} V. This is based on and generalizes the Minkowski decompositions for all wtL(λ)\mathrm{wt} L(\lambda) and hulls convR(wtV)\mathrm{conv}_{\mathbb{R}}(\mathrm{wt} V), of Khare [J. Algebra. 2016 & Trans. Amer. Math. Soc. 2017] and Dhillon-Khare [Adv. Math. 2017 & J. Algebra. 2022]. Those works need a freeness property of the Dynkin graph nodes of integrability JλJ_{\lambda} of L(λ)L(\lambda): wtL(λ) \mathrm{wt} L(\lambda)\ - any sum of simple roots over JλcJ_{\lambda}^c are all weights of L(λ)L(\lambda). We generalize it for all VV, by introducing nodes JVJ_V that record all the lost 1-dim. weights in VV. We show three applications (seemingly novel) for all (g,λ,V)\big(\mathfrak{g}, \lambda, V\big) of our JVcJ_V^c-freeness: 1) Minkowski decompositions of all wtV\mathrm{wt} V, subsuming those above for simples. 1') Characterization of these formulas. 1'') For these, we solve the inverse problem of determining all VV with fixing wtV =\mathrm{wt} V \ = weight-set of a Verma, parabolic Verma and L(λ)L(\lambda) \forall λ\lambda. 2) At module level (by raising operators' actions), construction of weight vectors along JVcJ_V^c-directions. 3) Lower bounds on the multiplicities of such weights, in all VV.

Keywords

Cite

@article{arxiv.2409.12802,
  title  = {Minkowski difference weight formulas},
  author = {G. Krishna Teja},
  journal= {arXiv preprint arXiv:2409.12802},
  year   = {2024}
}

Comments

We isolate from our pre-print (ArXiv:2012.07775v2), weight-formula in Theorem A and conversely finding modules V with classical weights in Theorem B. All such weight-formulas are found in Theorem C, via freeness-nodes for weights (Definitions 1.8, 5.2). Thereby: "Jordan-Holder series'' factors of V with majority of weights explicitly, and some weight multiplicity bounds (Proposition 1.16)

R2 v1 2026-06-28T18:50:20.251Z