We show that the 2-parameter Podles sphere is a q-fuzzy sphere precisely interpolating between the fuzzy sphere as quotient of the angular momentum algebra U(su2) and the standard q-sphere Cq [S] as subalgebra of the quantum group Cq [SU2]. Whereas the classical sphere as CP 1 can be defined as the algebra generated by the matrix entries of a projector e with trace(e) = 1, the fuzzy-sphere is d...

We find the Hopf algebra U g,h dual to the Jordanian matrix quantum group GL g,h (2). As an algebra it depends only on the sum of the two parameters and is split in two subalgebras: U ′ g,h (with three generators) and U (Z) (with one generator). The subalgebra U (Z) is a central Hopf subalgebra of U g,h. The subalgebra U ′ g,h is not a Hopf subalgebra and its coalgebra structure depends on both...

The maximal dimension of a commutative subalgebra of the Grassmann algebra is determined. It is shown that for any commutative subalgebra there exists an equidimensional commutative subalgebra spanned by monomials. It follows that the maximal dimension of a commutative subalgebra can be expressed in terms of the maximal size of an intersecting system of subsets of odd size in a finite set. 2010...

We discuss various aspects of the noncommutative geometry a smooth subalgebra Toeplitz algebra. In particular, we study structure derivations on this subalgebra.

A set E equipped with a partial, commutative and associative operation ⊕, containing elements 0 and 1, in which the existence of a unique inverse element x′ to any x ∈ E is guaranteed, and a⊕ 1 is admitted only if a = 0 is well known as effect algebra. Effect algebras were introduced by Foulis and Bennet [3] and simultaneously by Kôpka and Chovanec [7] as D-posets. An effect algebra equipped wi...

We consider the question of whether P(ω) is a subalgebra whenever it is a quotient of a Boolean algebra by a countably generated ideal. This question was raised privately by Murray Bell. We obtain two partial answers under the open coloring axiom. Topologically our first result is that if a zerodimensional compact space has a zero-set mapping onto βN , then it has a regular closed zero-set mapp...

The notions of coupled N -subalgebra, coupled (positive implicative) N -ideals of d-algebras are introduced, and related properties are investigated. Characterizations of a coupled N -subalgebra and a coupled (positive implicative) N -ideals of d-algebras are given. Relations among a coupled N -subalgebra, a coupled N -ideal and a coupled positive implicative N -ideal of d-algebras are discussed.

Let H be a finite dimensional semisimple Hopf algebra over an algebraically closed field of characteristic zero. In this note we give a short proof of the fact that a Hopf subalgebra of H is a depth two subalgebra if and only if it is normal Hopf subalgebra.