Character formulae for classical groups

Let $G(q)$ be a Chevalley group over a finite field $F_q$. By Lusztig's and Shoji's work, the problem of computing the values of the unipotent characters of $G(q)$ is solved, in principle, by the theory of character sheaves; one issue in this solution is the determination of certain scalars relating two types of class functions on $G(q)$. We show that this issue can be reduced to the case where $q$ is a prime, which opens the way to use computer algebra methods. Here, and in ...

We give a new formula for the values of an irreducible character of the symmetric group S_n indexed by a partition of rectangular shape. Some observations and a conjecture are given concerning a generalization to arbitrary shapes.

Frobenius observed that the number of times an element of a finite group is obtained as a commutator is given by a specific combination of the irreducible characters of the group. More generally, for any word w the number of times an element is obtained by substitution in w is a class function. Thus, it has a presentation as a combination of irreducible characters, called its Fourier expansion. In this paper we present formulas regarding the Fourier expansion of words in whic...

This is an essay about a certain family of elements in the general linear group GL(d,q) called primitive prime divisor elements, or ppd-elements. A classification of the subgroups of GL(d,q) which contain such elements is discussed, and the proportions of ppd-elements in GL(d,q) and the various classical groups are given. This study of ppd-elements was motivated by their importance for the design and analysis of algorithms for computing with matrix groups over finite fields. ...

The branching theorem expresses irreducible character values for the symmetric group $S_n$ in terms of those for $S_{n-1}$, but it gives the values only at elements of $S_n$ having a fixed point. We extend the theorem by providing a recursion formula that handles the remaining cases. It expresses these character values in terms of values for $S_{n-1}$ together with values for $S_n$ that are already known in the recursive process. This provides an alternative to the Murnaghan-...

We give an explicit expression of the normalized characters of the symmetric group in terms of the contents of the partition labelling the representation.

We give several formulas for the character of an arbitrary irreducible finite--dimensional representation for the Yangian of sl_2.

We derive several identities that feature irreducible characters of the general linear, the symplectic, the orthogonal, and the special orthogonal groups. All the identities feature characters that are indexed by shapes that are "nearly" rectangular, by which we mean that the shapes are rectangles except for one row or column that might be shorter than the others. As applications we prove new results in plane partitions and tableaux enumeration, including new refinements of t...

A known result for the finite general linear group $\GL(n,\FF_q)$ and for the finite unitary group $\U(n,\FF_{q^2})$ posits that the sum of the irreducible character degrees is equal to the number of symmetric matrices in the group. Fulman and Guralnick extended this result by considering sums of irreducible characters evaluated at an arbitrary conjugacy class of $\GL(n,\FF_q)$. We develop an explicit formula for the value of the permutation character of $\U(2n,\FF_{q^2})$ ov...

The aim of this paper is to give another proof of a theorem of D.Prasad, which calculates the character of an irreducible representation of $\text{GL}(mn,\mathbb{C})$ at the diagonal elements of the form $\underline{t} \cdot c_n$, where $\underline{t}=(t_1,t_2,\cdots,t_m)$ $\in$ $(\mathbb{C}^*)^{m}$ and $c_n=(1,\omega_n,\omega_n^{2},\cdots,\omega_n^{n-1})$, where $\omega_n=e^{\frac{2\pi \imath}{n}}$, and expresses it as a product of certain characters for $\text{GL}(m,\mathbb...