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Let ${\mathbf U}^-_q$ be the negative part of the quantum enveloping algebra associated to a simply laced Kac-Moody Lie algebra ${\mathfrak g}$, and $\underline{\mathbf U}^-_q$ the algebra corresponding to the fixed point subalgebra of ${\mathfrak g}$ obtained from a diagram automorphism $\sigma$ on ${\mathfrak g}$. Let ${\mathbf B}^{\sigma}$ be the set of $\sigma$-fixed elements in the canonical basis of ${\mathbf U}_q^-$, and $\underline{\mathbf B}$ the canonical basis of $\underline{\mathbf U}_q^-$. Lusztig proved that there exists a canonical bijection ${\mathbf B}^{\sigma} \simeq \underline{\mathbf B}$ based on his geometric construction of canonical bases. In this paper, we prove (the signed bases version of) this fact, in the case where ${\mathfrak g}$ is finite or affine type, in an elementary way, in the sense that we don't appeal to the geometric theory of canonical bases nor Kashiwara's theory of crystal bases. We also discuss the correspondence between PBW-bases, by using a new type of PBW-bases of ${\mathbf U}_q^-$ obtained by Muthiah-Tingley, which is a generalization of PBW-bases constructed by Beck-Nakajima., Comment: 43 pages

Let ${\mathbf U}_q^-$ be the negative part of the quantum enveloping algebra, and $\sigma$ the algebra automorphism on ${\mathbf U}_q^-$ induced from a diagram automorphism. Let $\underline{\mathbf U}_q^-$ be the quantum algebra obtained from $\sigma$, and $\widetilde{\mathbf B}$ (resp. $\widetilde{\underline{\mathbf B}}$) the canonical signed basis of ${\mathbf U}_q^-$ (resp. $\underline{\mathbf U}_q^-$). Assume that ${\mathbf U}_q^-$ is simply-laced of finite or affine type. In our previous papers [SZ1, 2], we have proved by an elementary method, that there exists a natural bijection $\widetilde{\mathbf B}^{\sigma} \simeq \widetilde{\underline{\mathbf B}}$ in the case where $\sigma$ is admissible. In this paper, we show that such a bijection exists even if $\sigma$ is not admissible, possibly except some small rank cases., Comment: 48 PAGES

Let $V$ be an $n$ dimensional vector space over an algebraic closure of a finite field $F_q$ and put $G = GL(V)$. For a positive integer $r$, we consider the variety $X_{uni} = G_{uni} \times V^{r-1}$, on which $G$ acts diagonally. $X_{uni}$ is the "unipotent part" of the enhanced variety of level $r$. $X_{uni}$ is partitioned into finitely many pieces $X_{\lambda}$ labelled by $r$-partitions $\lambda$ of $n$, and we consider the intersection cohomology $IC_{\lambda}$ associated to $X_{\lambda}$. In this paper, we show that the Frobenius trace functions (over $F_q$) associated to those $IC_{\lambda}$ satisfy certain orthogonality relations, which are very close to the equations characterizing the Kostka functions indexed by (a pair of) $r$-partitions. Using this we show, in some special cases, that the Kostka functions can be described in terms of those intersection cohomology, which is a (partial) generalization of the known results for the case $r = 1, 2$., Comment: v2: 52 pages. Proposition 6.3 was revised, and some examples were added in section 7. Final version, to appear in Transformation Groups

In this paper, we consider the set of r-symbols in a full generality. We construct Hall-Littlewood functions and Kostka functions associated to those r-symbols. We also discuss a multi-parameter version of those functions. We show that there exists a general algorithm of computing multi-parameter Kostka functions. As an application, we show that the generalized Green functions of symplectic groups can be described combinatorially in terms of those (one-parameter) Kostka functions., Comment: 28 pages, final version, to appear in J. of Algebra

Kostka functions $K^{\pm}_{\lambda, \mu}(t)$ associated to complex reflection groups are a generalization of Kostka polynomials, which are indexed by a pair $\lambda, \mu$ of $r$-partitions and a sign $+, -$. It is expected that there exists a close connection between those Kostka functions and the intersection cohomology associated to the enhanced variety $X$ of level $r$. In this paper, we study combinatorial properties of Kostka functions by making use of the geometry of $X$. In particular, we show that if $\mu$ is of the form $\mu = (-,\dots, -, \xi)$ and $\lambda$ is arbitrary, $K^-_{\lambda, \mu}(t)$ has a Lascoux-Sch\"utzenberger type combinatorial description., Comment: 21 pages

Let W be the complex reflection group G(e,1,n). In the author's previous paper, Hall-Littlewood functions associated to W were introduced. In the special case where W is a Weyl group of type B_n, they are closely related to Green polynomials of finite classical groups. In this paper, we introduce a two variables version of the above Hall-Littlewood functions, as a generalization of Macdonald functions associated to symmetric groups. A generalization of Macdonald operators is also constructed, and we characterize such functions by making use of Macdonald operators, assuming a certain conjecture., Comment: 22 pages

In our previous paper, Green functions associated to complex reflection groups G(e,1,n) were discussed. It involved a combinatorial approach to the Green functions of classical groups of type B_n or C_n. In this paper, we introduce Green functions associated to complex reflection groups G(e,p,n). We define Schur functions, Hall-Littlewood functions associated to G(e,p,n), and show that our Green functions are obtained as a transition matrix between those two kinds of symmetric functions. As a special case, it gives a combinatorial treatmnet of Green functions of type D_n., Comment: 33pages

Green functions of classical groups are determined by the data from Weyl groups and by certain combinatorial objects called symbols. Generalizing this, we define Green functions associated to complex reflection groups G(e, 1, n) and study their combinatorial properties. We construct Hall–Littlewood functions and Schur functions in our scheme and show that such Green functions are obtained as a transition matrix between those two symmetric functions, as in the case of GLn.

Let g = glm1 ⊕ ··· ⊕ glmr be a Levi subalgebra of glm, with m = ∑ri = 1mi, and V the natural representation of the quantum group Uq(g). We construct a representation of the Ariki–Koike algebra Hn, r on the n-fold tensor space of V, commuting with the action of Uq(g), and prove the Schur–Weyl reciprocity for the actions of Uq(g) and Hn, r on it.

In this paper, the Shintani descent of irreducible characters of finite special linear groups is discussed. We parametrize irreducible characters of SL n ( F q ) by making use of (modified) generalized Gelfand–Graev characters. Shintani descent of irreducible characters of SL n ( F q m ) is determined by investigating the Shintani descent of generalized Gelfand–Graev characters. Our results hold for arbitrary p and q .

Let V be an 2n-dimensional vector space over an algebraically closed field of odd characteristic. Let G = GL(V), and H = Sp(V) the symplectic group contained in G. For a positive integer r > 1, we conisder the variety X = G/H \times V^{r-1}, on which H acts diagonally. X is called the exotic symmetric space of level r. Let W_{n,r} be the complex reflection group G(r,1,n). In this paper, generalizing the result for the case where r = 2, we show that there exists a natural bijective correspondence (Springer correspondence) between the set of irreducible representations of W_{n,r} and a certain set of H-equivariant simple perverse sheaves on X_{uni}$, where X_{uni} is the "unipotent part" of X. We also consider a similar problem for G \times V^{r-1}, where G = GL(V) for a finite dimensional vector space V., 69 pages

We determine the constants appearing in the Lusztig conjecture in the case of unipotent characters of classical groupsG subject to the condition that the characteristic is odd and the center ofG is connected. This enables us to compute the character values of unipotent characters of such finite classical groups.

Let V be a 2n dimensional vector space over an algebraically closed field of odd characteristic. Let G = GL(V) and H = Sp_{2n} be the symplectic group contained in G. We call X = G/H \times V the exotic symmetric space, since its "unipotent" part is isomorphic to Kato's exotic nilcone. Let W be the Weyl group of type C_n. Kato established the Springer correspondence between irreducible characters of W and H-orbits in the exotic nilcone, based on the Ginzburg theory of affine Hecke algebras. In this paper, we develpoe a theory of character sheaves on X, and give an alternate proof for the Springer correspondence based on the theroy of character sheaves., 56 pages, the proof of Proposition 4.8 revised, and typos corrected. The results unchanged

In our earlier work, we have proved a product formula for certain decomposition numbers of the cyclotomic v-Schur algebra associated to the Ariki-Koike algebra. It is conjectured by Yvonne that the decomposition numbers of this algebra can be described in terms of the canonical basis of the higher level Fock space studied by Uglov. In this paper we prove a product formula related to the canonical basis of the Fock space. In view of Yvonne's conjecture, this formula is regarded as a counter-part for the Fock space of our previous formula., 24 pages

Let G be a simple algebraic group over C with the Weyl group W. For a unipotent element u of G, let B_u be the variety of Borel subgroups of G containing u. Let L be a Levi subgroup of a parabolic subgroup of G with the Weyl subgroup W_L. Assume that u is in L and let B_u^L be the corresponding variety for L. The induction theorem of Springer representations describes the W-module structure of H*(B_u) in terms of the W_L-module structure of H*(B_u^L). In this paper, we prove a certain refinement of the induction theorem by considering the action of a cyclic group of order e on H^*(B_u). As a corollary, we obtain a description of the values of Green functions at e-th root of unity., 18 pages. In this revised version, some errors are corrected. In particular some restrictions are added to the main results

(1982). On the green polynomials of a chevalley group of type f4. Communications in Algebra: Vol. 10, No. 5, pp. 505-543.

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(1980). On the springer representations of chevalley groups op type f4. Communications in Algebra: Vol. 8, No. 5, pp. 409-440.

(1979). On the springer representations of the weyl groups of classical algebraic groups. Communications in Algebra: Vol. 7, No. 16, pp. 1713-1745.

Let U q ( gl m ⊕ p ) be the quantized universal enveloping algebra of gl m ⊕ p . Let θ be the automorphism of U q ( gl m ⊕ p ) which is defined on generators by E i ↦ E i − m , F i ↦ F i − m , K j ↦ K j − m for any i ∈ Z / p m Z ∖ { 0 ¯ , m ¯ , … , ( p − 1 ) m ¯ } and any j ∈ Z / p m Z . Let H ( p , p , n ) be the Hecke algebra of type G ( p , p , n ) with parameters q , e , where e is a primitive pth root of unity. In this paper we establish a Schur–Weyl reciprocity between H ( p , p , n ) and a twisted tensor product of U q ( gl m ⊕ p ) and the group algebra for 〈 θ 〉 (a cyclic group of order p) by using the results in [J. Hu, J. Algebra 274 (2004) 446–490].

Let H n, r be the Ariki–Koike algebra associated to the complex reflection group Wn, r = G(r, 1, n). In this paper, we give a new presentation of H n, r by making use of the Schur–Weyl reciprocity for H n, r established by M. Sakamoto and T. Shoji (1999, J. Algebra, 221, 293–314). This allows us to construct various non-parabolic subalgebras of H n, r. We construct all the irreducible representations of H n, r as induced modules from such subalgebras. We show the existence of a partition of unity in H n, r, which is specialized to a partition of unity in the group algebra C Wn, r. Then we prove a Frobenius formula for the characters of H n, r, which is an analogy of the Frobenius formula proved by A. Ram (1991, Invent. Math.106, 461–488) for the Iwahori–Hecke algebra of type A.