scholarly journals CLASSIFYING COALGEBRA SPLIT EXTENSIONS OF HOPF ALGEBRAS

2013 ◽  
Vol 12 (05) ◽  
pp. 1250227
Author(s):  
A. L. AGORE ◽  
C. G. BONTEA ◽  
G. MILITARU
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Infinite Family ◽  
Crossed Products ◽  
Primitive Elements ◽  
Characteristic P ◽  
Generators And Relations ◽  
Split Extensions ◽  
Groups Of Automorphisms

For a given Hopf algebra A we classify all Hopf algebras E that are coalgebra split extensions of A by H4, where H4is the Sweedler's four-dimensional Hopf algebra. Equivalently, we classify all crossed products of Hopf algebras A# H4by computing explicitly two classifying objects: the cohomological "group" [Formula: see text] and CRP (H4, A) ≔ the set of types of isomorphisms of all crossed products A# H4. All crossed products A# H4are described by generators and relations and classified: they are parameterized by the set [Formula: see text] of all central primitive elements of A. Several examples are worked out in detail: in particular, over a field of characteristic p ≥ 3 an infinite family of non-isomorphic Hopf algebras of dimension 4p is constructed. The groups of automorphisms of these Hopf algebras are also described.

Separable extensions for crossed products over monoidal Hom-Hopf algebras

2018 ◽  
Vol 17 (09) ◽  
pp. 1850161 ◽  
Author(s):  
Zhongwei Wang ◽  
Yuanyuan Chen ◽  
Liangyun Zhang
Keyword(s):  
Hopf Algebra ◽  
Galois Extension ◽  
Hopf Algebras ◽  
Crossed Products ◽  
Separable Extensions

Let [Formula: see text] be a Frobenius monoidal Hom-Hopf algebra, and [Formula: see text] an [Formula: see text]-Hom-Hopf Galois extension of [Formula: see text]. We prove that the separability of the Hom-algebra extension [Formula: see text] is equivalent to the existence of a trace one element [Formula: see text] that centralizes [Formula: see text]. As applications, we obtain the differentiated conditions for the extension [Formula: see text] to be separable, and deduce a Doi’s result of Hom-type.

scholarly journals Comparison of two notions of weak crossed product

2020 ◽  
pp. 2150059
Author(s):  
Jorge A. Guccione ◽  
Juan J. Guccione
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Crossed Product ◽  
Weak Hopf Algebra ◽  
Crossed Products ◽  
Hopf Algebroid ◽  
Hopf Algebroids ◽  
Weak Crossed Product ◽  
Cleft Extensions ◽  
Weak Hopf Algebras

We compare the restriction to the context of weak Hopf algebras of the notion of crossed product with a Hopf algebroid introduced in [Cleft extensions of Hopf algebroids, Appl. Categor. Struct. 14(5–6) (2006) 431–469] with the notion of crossed product with a weak Hopf algebra introduced in [Crossed products for weak Hopf algebras with coalgebra splitting, J. Algebra 281(2) (2004) 731–752].

scholarly journals Entropic Hopf algebras

10.29007/39rd ◽  
2018 ◽  
Author(s):  
Anna Romanowska ◽  
Jonathan Smith
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Probability Distributions ◽  
Commutative Rings ◽  
Group Algebras ◽  
Tensor Algebra ◽  
Primitive Elements ◽  
Commutative Monoids ◽  
Algebraic Setting ◽  
Grouplike Element

Classically, Hopf algebras are defined on the basis of modules over commutative rings. The present study seeks to extend the Hopf algebra formalism to a more general universal-algebraic setting, entropic varieties, including (pointed) sets, barycentric algebras, semilattices, and commutative monoids. The concept of a setlike (or grouplike) element may be defined, and group algebras constructed, in any such variety. In particular, group algebras within the variety of barycentric algebras consist precisely of finitely supported probability distributions on groups. For primitive elements and group quantum doubles, the natural universal-algebraic classes are entropic Jónsson-Tarski varieties (such as semilattices or commutative monoids). There, the tensor algebra on any algebra is a bialgebra, and the set of primitive elements of a Hopf algebra forms an abelian group. Coalgebra congruences on comonoids in entropic varieties are also studied.

scholarly journals COQUASITRIANGULAR STRUCTURES FOR EXTENSIONS OF HOPF ALGEBRAS. APPLICATIONS

2012 ◽  
Vol 55 (1) ◽  
pp. 201-215 ◽  
Author(s):  
A. L. AGORE
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Quantum Double ◽  
Bijective Correspondence ◽  
Infinite Dimensional ◽  
Main Application ◽  
Split Extensions ◽  
Necessary And Sufficient

AbstractLet A ⊆ E be an extension of Hopf algebras such that there exists a normal left A-module coalgebra map π : E → A that splits the inclusion. We shall describe the set of all coquasitriangular structures on the Hopf algebra E in terms of the datum (A, E, π) as follows: first, any such extension E is isomorphic to a unified product A ⋉ H, for some unitary subcoalgebra H of E (A. L. Agore and G. Militaru, Unified products and split extensions of Hopf algebras, to appear in AMS Contemp. Math.). Then, as a main theorem, we establish a bijective correspondence between the set of all coquasitriangular structures on an arbitrary unified product A ⋉ H and a certain set of datum (p, τ, u, v) related to the components of the unified product. As the main application, we derive necessary and sufficient conditions for Majid's infinite-dimensional quantum double Dλ(A, H) = A ⋈τH to be a coquasitriangular Hopf algebra. Several examples are worked out in detail.

COREPRESENTATION THEORY OF MULTIPLIER HOPF ALGEBRAS II

2000 ◽  
Vol 11 (02) ◽  
pp. 233-278 ◽  
Author(s):  
HIDEKI KUROSE ◽  
ALFONS VAN DAELE ◽  
YINHUO ZHANG
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Covariant Theory ◽  
Crossed Products ◽  
Quantum Double ◽  
Multiplier Algebra ◽  
Algebraic Quantum ◽  
Multiplier Hopf Algebras ◽  
Multiplier Hopf Algebra ◽  
Invertible Elements

We continue our development of the corepresentation theory of multiplier Hopf algebras. In this paper, we consider the corepresentations of a multiplier Hopf algebra A in a nondegenerate algebra B rather than on a vector space (cf. [25]). We concentrate ourself on those corepresentations of A in B which are invertible elements of the multiplier algebra M(B⊗A). They are called the unitary corepresentations of A. In particular, the generalized R-matrices or quasi-triangular structures of a regular multiplier Hopf algebra are unitary (bi)corepresentations. As an application the quantum double of an algebraic quantum group can be constructed by means of the universal unitary corepresentation. Moreover, a unitary corepresentation of A in B can implement an inner coaction of A on B which allows us to study the covariant theory and crossed products.

scholarly journals Crossed products of Hom-Hopf algebras

Filomat ◽  
2020 ◽  
Vol 34 (4) ◽  
pp. 1295-1313
Author(s):  
Daowei Lu ◽  
Yizheng Li ◽  
Shuangjian Guo
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Crossed Product ◽  
Crossed Products ◽  
Cleft Extension ◽  
Necessary And Sufficient

Let (H,?) be a Hom-Hopf algebra and (A,?) be a Hom-algebra. In this paper we will construct the Hom-crossed product (A#?H???), and prove that the extension A ? A#?H is actually a Hom-type cleft extension and vice versa. Then we will give the necessary and sufficient conditions to make (A#?H???) into a Hom-Hopf algebra. Finally we will study the lazy 2-cocycle on (H,?).

scholarly journals Handlebody-knot invariants derived from unimodular Hopf algebras

2014 ◽  
Vol 23 (07) ◽  
pp. 1460001 ◽  
Author(s):  
Atsushi Ishii ◽  
Akira Masuoka
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Tensor Category ◽  
Symmetric Algebra ◽  
Computational Results ◽  
Drinfeld Modules ◽  
Generators And Relations ◽  
Knot Invariants ◽  
Finite Dimensional ◽  
Tensor Functor

To systematically construct invariants of handlebody-links, we give a new presentation of the braided tensor category [Formula: see text] of handlebody-tangles by generators and relations, and prove that given what we call a quantum-commutative quantum-symmetric algebra A in an arbitrary braided tensor category [Formula: see text], there arises a braided tensor functor [Formula: see text], which gives rise to a desired invariant. Some properties of the invariants and explicit computational results are shown especially when A is a finite-dimensional unimodular Hopf algebra, which is naturally regarded as a quantum-commutative quantum-symmetric algebra in the braided tensor category [Formula: see text] of Yetter–Drinfeld modules.

Primitive Generators for Algebras

1982 ◽  
Vol 34 (2) ◽  
pp. 454-465
Author(s):  
Stanley O. Kochman
Keyword(s):  
Hopf Algebra ◽  
Commutative Algebra ◽  
Hopf Algebras ◽  
Primitive Elements ◽  
Explicit Formulas ◽  
Recursive Computation

LetHbe a graded commutative algebra with a nice set of algebra generators. LetHalso be a comodule over a Hopf algebraA. In Section 2 we give conditions under which certain of these generators ofHcan be rechosen to be primitive. In addition we give explicit formulas expressing these primitive generators in terms of the original set of generators.In Section 3 we apply the theory of Section 2 to the modphomology of the Thorn spectraMO, MUandMSp.In particular we give two explicit descriptions of the image of the Hurewicz homomorphism forMO.One of these makes explicit the recursive computation of E. Brown and F. Peterson [1].In Section 4 we give a variation of the theory of Section 2 which computes primitive generators of certain Hopf algebras. This theory is applied to study the primitive elements ofH*(BU)andH*(SO;Z2).

scholarly journals A note on split extensions of bialgebras

2018 ◽  
Vol 30 (5) ◽  
pp. 1089-1095 ◽  
Author(s):  
Xabier García-Martínez ◽  
Tim Van der Linden
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Closed Field ◽  
Split Extension ◽  
Algebraically Closed Field ◽  
Split Extensions

AbstractWe prove a universal characterization of Hopf algebras among cocommutative bialgebras over an algebraically closed field: a cocommutative bialgebra is a Hopf algebra precisely when every split extension over it admits a join decomposition. We also explain why this result cannot be extended to a non-cocommutative setting.

scholarly journals Hopf algebras and skew PBW extensions

2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Luis Alfonso Salcedo Plazas
Keyword(s):  
Hopf Algebra ◽  
Hopf Algebras ◽  
Ore Extensions ◽  
Skew Pbw Extensions

In this article we relate some Hopf algebra structures over Ore extensions and over skew PBW extensions ofa Hopf algebra. These relations are illustrated with examples. We also show that Hopf Ore extensions andgeneralized Hopf Ore extensions are Hopf skew PBW extensions.

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