arXiv subjects
Publications and source records attributed to T H Lenagan.
A general method is developed for deriving Quantum First and Second Fundamental Theorems of Coinvariant Theory from classical analogs in Invariant Theory, in the case that the quantization parameter q is transcendental over a base field. Several examples are given illustrating the utility of the method; these recover earlier results of various researchers including Domokos, Fioresi, Hacon, Rigal, Strickland, and the present authors.
We develop a method of reducing the size of quantum minors in the algebra of n x n quantum matrices. The method is used to show that quantum determinantal factor rings of n x n quantum matrices over the complex numbers are maximal orders, when the parameter q is transcendental over the rational numbers.
The m x n quantum grassmannian, G_q(m,n), is the subalgebra of the algebra of m x n quantum matrices that is generated by the maximal m x m quantum minors. Several properties of G_q(m,n) are established. In particular, a basis of G_q(m,n) is obtained, and it is shown that G_q(m,n) is a noetherian domain of Gelfand-Kirillov dimension m(n-m)+1. The algebra G_q(m,n) is identified as the subalgebra of coinvariants of a natural left coaction of the m x m quantum special linear group on the algebra of m x n quantum matrices and it is shown that G_q(m,n) is a maximal order.
A condition is identified which guarantees that the coinvariants of a coaction of a Hopf algebra on an algebra form a subalgebra, even though the coaction may fail to be an algebra homomorphism. A Hilbert Theorem (finite generation of the subalgebra of coinvariants) is obtained for such coactions of a cosemisimple Hopf algebra. This is applied to two adjoint coactions of quantized function algebras of classical groups on the associated FRT bialgebra. Provided that the Hopf algebra is cosemisimple and coquasitriangular, the algebras of coinvariants form two finitely generated, commutative, graded subalgebras which have the same Hilbert series. Consequently, the cocommutative elements and the S^2-cocommutative elements in the Hopf algebra form finitely generated subalgebras. A Hopf algebra monomorphism from the quantum general linear group to Laurent polynomials over the quantum special linear group is found and used to explain the strong relationship between the corepresentation (and coinvariant) theories of these quantum groups.