Quantum Multilinear Algebra
Quantum Multilinear Algebra
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DOI:
10.2748/tmj/1178227246
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发表时间:
1992-12
影响因子:
0.5
通讯作者:
M. Hashimoto;T. Hayashi
中科院分区:
文献类型:
--
作者:
M. Hashimoto;T. Hayashi
We construct a quantized version of the theory of multilinear algebra, based on Jimbo's solution of Yang-Baxter equation of type Λ#l 1. Using this, we discuss the polynomial representations of quantum general linear groups. CONTENTS Introduction 471 1. Yang-Baxter operators 473 2. Algebras associated with Yang-Baxter pairs 476 3. Quantum matrices 477 4. Symmetric algebras, exterior algebras and the fusion procedure 480 5. Divided power algebra 486 6. Schur modules and Weyl modules 493 7. Universality of Weyl modules 505 8. Polynomial representation of GLq over a field 510 9. Quantum determinants and straightening formulas 515 References 519 Introduction. Quantum groups are mathematical objects which arose from the study of the quantum inverse scattering method, especially the Yang-Baxter equation. They are very remarkable Hopf algebras and can be considered as {/-analogues of Kac-Moody enveloping algebras or of coordinate rings of Lie groups. Not only have they added new aspects to representation theory, but also they have brought to non-commutative geometry a remarkable progress, i.e. the discovery of many new examples such as quantum linear algebraic groups, quantum spheres and so on. In this article, we study quantum analogues of some linear-algebraic objects such as matrices, symmetric and alternating tensors, and determinants. We construct these from Jimbo's solution of Yang-Baxter (YB) equation of type Atfl. x and investigate their structure via the notion which we call Yang-Baxter bίalgebras. As applications, we give realizations and free bases of Weyl modules KλVand their dual modules (Schur modules) of quantum general linear groups GLq(N), and give a criterion for the irreducibility of KλV. We also give an analogue of the straightening formula for quantum matric bialgebras. We would like to emphasize that these objects are defined over any commutative ring R and any unit element q e R and are compatible with extensions 1991 Mathematical Subject Classification. Primary 16W30. 472 M. HASHIMOTO AND T. HAYASHI of the base ring R. Hence, we can get the representation theory of quantum general group 'defined over Z[Q, β"]', where Q denotes an indeterminate. In Section 1, we introduce operations on YB operators (i.e. solutions of the YB equation) called the product x , dual , and fusion procedure. In Section 2, we associate with a YB operator two algebras which we call the symmetric and the exterior algebras. In Section 3, we apply these tools to the construction of bialgebras SE which are called quantum matric bialgebras (cf. [12]). In Section 4, we construct two YB operators φ and ψ on the symmetric and exterior algebras of Jimbo's YB operators of type Aftϊ. j using the fusion procedure. With the YB operator φ, we introduce unusual algebra structures into tensor products of these algebras, and prove that these algebras have some structures which we call YB-bialgebras. Though a YB-bialgebra has structures of an algebra and a coalgebra, it is not necessarily a bialgebra in the usual sense. The 'commutativity' and the 'cocommutativity' of these YB-bialgebras are described in terms of the YB-operator ψ. In Section 5, we discuss an analogue of the theory of graded multilinear bialgebras. Recall that divided power algebras have been important in the study of characteristicfree representation theory (cf. [2], [3], [4]). Here we introduce divided power algebras of the YB pairs treated in Section 4. They are defined to be graded duals of symmetric algebras defined in Section 4. This concept enables us to define Weyl modules and Schur algebras in a natural way without assuming that q is not a root of unity. From Sections 6 to 9, our interest is concentrated on the study of the representation theory of quantum deformations of general linear groups. In Section 6, we define (deformed) Weyl modules KλV and Schur modules LλV associated to a partition λ, using the YB-bialgebra structure of the symmetric and exterior algebras defined in Section 4. We prove that LλV and KλV are finite free /^-modules and that they are 'defined over Z[Q, β"]' in the sense that they are compatible with base extensions. This property is an analogue of the so-called universal freeness. For the original version of this result, we refer the reader to [4]. Though our definition of LλV is different from L λ q(B) in Taft-Towber [37], they will turn out to be equivalent (cf. Proposition 9.7). Though our construction and argument in this section are nothing but the deformed versions of those in [4, Chapter II], we include some details, since they do not seem to be so obvious. In Section 7, we introduce the deformed versions of the Schur algebra, weights, and the contravariant dual functor in our language. We will show that (deformed) Weyl modules are universal highest weight modules in the sense of Theorem 7.12. In Section 8, we work over a base field K, and discuss the irreducibility and complete reducibility of SΈ-comodules. The notion of formal characters is introduced in this section. Theorem 8.9 is a ^-analogue of the hook length criterion for the irreducibility of Weyl modules. In the proof, Gyoja's ^-analogues of Young symmetrizers [14] play important roles. In Section 9, we prove a ^-analogue of the straightening formula using quantum deQUANTUM MULTILINEAR ALGEBRA 473 terminants. Namely, we prove that the degree k component SkE v of SE v admits a filtration of SE v -subbicomodules whose associated graded object is ©\λ\=k(KλV)*LχV, where λ is the transpose of λ. This formula was originated by Doubilet-Rota-Stein [11] in the case q=l. Our approach is a ^-analogue of the treatment in [4]. Lastly, we remark on the relation between our construction and the quantum enveloping algebra UqQl(N), or rather the "quantum hyperalgebra" such as that defined in Lusztig [23]. Since these Hopf algebras satisfy the conditions in Theorem 3.3, there are pairings of bialgebras between the quantum matrix bialgebra over Jimbo's YB pair of type Atfl. x and the quantum hyperalgebra. Hence, thanks to the general theory of bialgebras, the quantum hyperalgebra acts on our Schur and Weyl modules. Moreover, the criterion for the irreducibility (Theorem 8.9) is also valid when they are viewed as representations over the quantum hyperalgebra. After the submission of the first version of this work, the authors received preprints by DipperJames [10], Noumi-Yamada-Mimachi [29], Parshall-Wang [30], which have some overlap with our paper. Our special thanks are due to Professors Mitsuo Hoshino, Yukihiro Kanie, Hideyuki Matsumura and Akihiro Tsuchiya for valuable advice. 1. Yang-Baxter operators. Let V be a free /^-module. A Yang-Baxter (or YB) operator on V is an automorphism βveEndR(V® V} such that (1.1) (βV)l°(βv)2°(βvϊl=(βv)2°(βv)l°(βV)2, A Yang-Baxter pair V=(V9 βv) is a free /^-module V equipped with a Yang-Baxter operator βv on V. Here we give some examples of Yang-Baxter pairs. EXAMPLE (1) (trivial twisting). Let K be a free ^-module. Then the map τv : = τv Y defined by τv(u®u') = u l ®u is a YB operator on V. We call τv the trivial twisting on V. EXAMPLE (2) (Jimbo's operators of type A^l.^. Let K be a free /^-module with a basis {ui9 u2, . . . , UN} and let q be an invertible element of R. Then Jimbo's YB operators of type A^_ l is the map defined by the following formula: (1.2) (ί >j} . We call {wj the standard basis of (F, βv). This operator also satisfies Iwahori's quadratic equation