对称群中在特征2下与线性特征标成比例的旋量特征标
Spin characters of the symmetric group which are proportional to linear characters in characteristic 2
AI总结:
本文研究对称群双重覆盖在特征2下的表示约化问题,确定不可约旋量表示的2-模Brauer特征标何时与Specht模成比例,并利用归纳和限制函子构造了交换算盘游标的函数。
摘要:
对于有限群,确定两个普通不可约表示何时具有相同的 $p$-模约化是一个有趣的问题;即特征 $p$ 下分解矩阵的两行何时相等,或等价地,相应的 $p$-模 Brauer 特征标何时相同。我们通过确定不可约旋量表示的 $2$-模约化何时与 $2$-模 Specht 模一致,完成了对称群双重覆盖在 $p=2$ 时的这一任务。事实上,我们得到了一个更一般的结果:确定了不可约旋量表示的 $2$-模 Brauer 特征标何时与 Specht 模成比例。在证明过程中,我们使用归纳和限制函子构造了广义特征标上的一个函数,其效果是在标记分区的算盘显示中交换游标。
英文摘要:
For a finite group, it is interesting to determine when two ordinary irreducible representations have the same $p$-modular reduction; that is, when two rows of the decomposition matrix in characteristic $p$ are equal, or equivalently when the corresponding $p$-modular Brauer characters are the same. We complete this task for the double covers of the symmetric group when $p=2$, by determining when the $2$-modular reduction of an irreducible spin representation coincides with a $2$-modular Specht module. In fact, we obtain a more general result: we determine when an irreducible spin representation has $2$-modular Brauer character proportional to that of a Specht module. In the course of the proof, we use induction and restriction functors to construct a function on generalised characters which has the effect of swapping runners in abacus displays for the labelling partitions.
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