Margaret Beattie, Daniel Bulacu, Blas Torrecillas, Radford's S^4 formula for
co-Frobenius Hopf algebras,
J. Algebra 307 (2007), 330-342. Preprint is posted on
Mathematics ArXiv ,
The interested reader might also like to consult
(for weak Hopf algebras) Peter Vecsernyes, Larson-Sweedler theorem and the role of grouplike elements
in weak Hopf algebras, J. Alg. 270
(2003), 471-520
(for multplier Hopf algebras) L. Delvaux, A. Van Daele, Shuanhong Wang, A note on Radford's S^4 formula,
Mathematics ArXiv
(for biFrobenius algebras) Walter Ferrar Santos and Mariana Haim, Radford's formula for biFrobenius algebras
and applications,
Mathematics ArXiv
M. Beattie and C. Weatherby,
Student Research Project: Integer Points on a Hyperboloid of One Sheet,
The College Mathematics Journal, Vol. 37, No 1, January 2006.
M. Beattie and C. Weatherby, Pythagorean triples and units
of integral group rings , Journal of Algebra and its Applications, Vol.4, No.4, 2005, 355-367.
A preprint
form is available in
pdf format.
N. Andruskiewitsch and M.
Beattie, Irreducible representations of liftings of quantum planes, in "Lie Theory and its Applications in Physics V",
Proceedings of the Fifth International Workshop, Varna, Bulgaria, 2003, Edit. H-D Doebner & V K Dobrev, World Scientific, 2004.
This paper is available at Mathematics arXiv.
N. Andruskiewitsch and M.
Beattie, The coradical of the dual of a lifting of a quantum
plane, in "Hopf algebras", edited by J. Bergen, S. Catoiu, W. Chin, Proceedings of the International Conference on Hopf
algebras and quantum groups, DePaul Univ., 2004, 47-63.
A preprint
form is available in
pdf format.
M. Beattie, S. D\u{a}sc\u{a}lescu, Hopf algebras of dimension 14, J.London Math. Soc (2004), 1-14.
Mathematics ArXiv QA/0205243
Margaret Beattie, Sorin D\u{a}sc\u{a}lescu, Serban Raianu,
Lifting of Nichols Algebras of Type $B_2$, with an Appendix: A generalization of the q-binomial theorem.
Appendix with Ian Rutherford ,Isreal J. Math.(2002), 1-28, Mathematics ArXiv QA/0204075
M. Beattie, Duals of pointed Hopf algebras ,
Journal of Algebra, Volume 262, Issue 1, 1 April 2003, Pages 54-76
Mathematics ArXiv QA/0202091
M. Beattie, S. Dascalescu and S. Raianu ,
A co-Frobenius Hopf algebra with a separable
Galois extension is finite.
Proc. Amer. Math. Soc. 128. No 11, 3201-3203.
Abstract: If H is a co-Frobenius Hopf algebra over a field, having a Galois H-object A which is separable
over AcoH, its ring of coinvariants, then H is finite-dimensional.
A preprint
form is available in
dvi format.
Margaret Beattie and Blas Torrecillas, Twistings and Hopf Galois extensions
J. Algebra 232 (2000)nr.2 p 673-696
Abstract:
Let k be a commutative ring, H a k-Hopf algebra,
and A a right H-comodule algebra. A twisting of A
is a map \tau: H \otimes A \to A such that (A,*_{\tau},
\rho_A) is also an H-comodule algebra , where the product
*_{\tau} is defined by a*_{\tau}b = \sum a_0 \tau(a_1 \otimes
b). In this note,
we observe that there is a map of pointed sets from the
twistings of A to the H-measurings from AcoH to A
and study the set of twistings that map to the trivial
measuring. If A/AcoH is Galois and H is finitely
generated projective, then the twistings that map to the trivial
measuring can
be described as a set of invertible twisted cocycles
\varphi: H \otimes H \to A. An equivalence relation on the set of
twisted cocycles corresponds to isomorphism classes of Galois extensions.
A preprint version is available in dvi format.
M. Beattie, S. Dascalescu, L. Grunenfelder,
Constructing pointed Hopf algebras by Ore extensions,
J. Algebra 225(2000) nr.2 p.743-770
Abstract:
We present a general construction producing pointed co-Frobenius Hopf algebras and
give some classification results for the examples obtained.
A preprint version is available in
dvi format.
M. Beattie, An isomorphism theorem for Ore extension
Hopf algebras, Communications in Algebra 28(2) (2000),
p.569-584.
Abstract: A complete description of isomorphisms between
Ore extension Hopf algebras is given and used to
enumerate all Ore extension Hopf algebras H with
the order of G(H) equal to 4 and skew-primitives
with square in H0.
A preprint version is
available in dvi format.
M. Beattie, S. Dascalescu, L. Grunenfelder,
On pointed Hopf algebras of dimension pn,
Proc. Amer. Math. Soc. 128 (1999), 361-367.
Abstract: In this note we describe non-semisimple Hopf algebras of dimension pn with coradical isomorphic to kC, C abelian of order pn-1, over an algebraically closed field k of characteristic zero. If C is cyclic or C = (Cp)n-1 then we also determine the number of isomorphism classes of such Hopf algebras.
A preprint version is available in
dvi format.
M. Beattie, S. Dascalescu,
L. Grunenfelder, On the number of types of finite
dimensional Hopf algebras , Inventiones Mathematicae
136 (1999), p.1-7.
Abstract: For an odd prime p we construct an
infinite class of non-isomorphic Hopf algebras of
dimension p4 over an infinite field
containing primitive p-th roots of unity, answering
in the negative a long standing conjecture of Kaplansky.
A preprint version is available in
dvi format.
M. Beattie and Ángel del Río,
Graded equivalences and Picard groups, Journal of Pure
and Applied Algebra 141 (1999) p.131-152
Abstract: We study two subgroups of the Picard group Pic(R-gr) of a category of graded modules:
the subgroup gr-Pic(R#P_G) of classes of graded equivalences and the subgroup Pic(R#P_G)G of
classes of equivalences which commute with the suspensions in Pic(R-gr). We prove that in general these
groups are not the same and show that they are related by
an exact sequence of cohomology.
A preprint version is available in
dvi format.
Some related papers are posted on the web page for ring theory preprints from Spanish universities.
M. Beattie, S. D\u{a}sc\u{a}lescu, S. Raianu and F. Van Oystaeyen,
Crossed modules and two-sided two co-sided Hopf modules, Appl. Categorical Structures 6(1998), 223-237.
M. Beattie, S. D\u{a}sc\u{a}lescu, L. Gr\"{u}nenfelder and C. N\u{a}st\u{a}sescu, Finiteness conditions, co-Frobenius Hopf algebras and
quantum groups, J. Algebra 200 (1998), 312-333.
M. Beattie, S. D\u{a}sc\u{a}lescu and S. Raianu, Galois extensions for co-Frobenius Hopf algebras, J. Algebra 198(1997),164-183.
M. Beattie, C. Y. Chen and J. J. Zhang, Twisted Hopf comodule algebras, Comm. Alg. 24 (1996), 1759-1775.
M. Beattie and A. del Río, The Picard group of a category of graded modules, Comm. Alg. 24 (1996), 4397-4414.
M. Beattie and S. D\u{a}sc\u{a}lescu, Categories of modules graded by
G-sets.
Applications. J. Pure & Appl. Alg. 107 (1996), 129-139.
M. Beattie, S. D\u{a}sc\u{a}lescu and C. N\u{a}st\u{a}sescu, Graded semilocal
rings, Rev. Romaine Math. Pures Appl. 40 (1995), 253-258.
M. Beattie, Cocycles and right crossed products, in `Rings, Extensions, and Cohomology',
Proceedings of conference in
honour of D. Zelinsky, Marcel Dekker, 1994, 19-29.
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