Journal of Combinatorial Theory Series A ( IF 0.9 ) Pub Date : 2021-07-27 , DOI: 10.1016/j.jcta.2021.105512 Sheila Sundaram 1
We define, for each subset S of the set of primes, an -module with interesting properties. is the well-known representation of afforded by the free Lie algebra, while is the module of the conjugacy action of on n-cycles. For arbitrary S the module interpolates between the representations and . We consider the symmetric and exterior powers of . These are the analogues of the higher Lie modules of Thrall. We show that the Frobenius characteristic of these higher modules can be elegantly expressed as a multiplicity-free sum of power sums. In particular this establishes the Schur positivity of new classes of sums of power sums.
More generally, for each nonempty subset T of positive integers we define a sequence of symmetric functions of homogeneous degree n. We show that the series can be expressed as symmetrised powers of the functions , analogous to the higher Lie modules first defined by Thrall. This in turn allows us to unify previous results on the Schur positivity of multiplicity-free sums of power sums, as well as investigate new ones. We also uncover some curious plethystic relationships between , the conjugacy action and the Lie representation.
中文翻译:
更高留置权模块的主要功率变化
我们定义,每个子Ş集 素数,一个 -模块 具有有趣的特性。 是众所周知的表示 的 由自由李代数提供,而 是模块 的共轭作用 在n 次循环上。对于任意S模块 在表示之间进行插值 和 . 我们考虑对称的和外部的权力. 这些是萨尔的高级谎言模块的类似物。我们证明了这些较高的 Frobenius 特征模块可以优雅地表示为幂和的无多重和。特别是这建立了新类别的幂和的舒尔正性。
更一般地,对于正整数的每个非空子集T,我们定义一个对称函数序列齐次n。我们证明该系列 可以表示为函数的对称幂 ,类似于由 Thrall 首先定义的更高的 Lie 模块。这反过来又使我们能够统一先前关于无多重幂和之和的 Schur 正性的结果,并研究新的结果。我们还发现了一些奇怪的丰满关系,共轭作用和谎言表示。