COMMUNICATIONS IN ALGEBRA Volume 30, Number 1, 2002
CONTENTS
On the Center of the Pro] of A Three Dimensional Regular
Algebra . . . 1 M. Van Gastel
A Simple Nil Ring Exists. . . . 27 A. Smoktunowicz
Picard Lattices of Families of K3 Surfaces. . . . 61
S.-M. Belcastro
Tilting Complexes Defined by Idempotents. . . . 83 M. Hoshino and Y. Kato
Derivations with Quantum Group Action . . . 101 U. Hermisson
Algebras Generated by Idempotents and Commutative Group
Algebras over a Ring. . . . 119 H. Kawai
Sur les Algebres d'Heisenberg Quantiques . . . 129 L. Ben Yakoub, L. El Kaoutit, and M. P. Malliavin
Semidirect Products of Ordered Semigroups. . . . 149 J.-E. Pin and P. Weil
Centers of Down-Up Algebras over Fields of Prime
C h a r a c t e r i s t i c . . . 171 J'. Hildebrand
Classification of Involutions of Sl(2, k) ... 193 A. G. Helminck and L. Wu
Stable Equivalences and Stable Grothendieck Groups . . . 205
A. Beligiannis
Lex-Segment Ideals and the Maximal Growth of Hilbert
F u n c t i o n s . . . 237 K. J . Presser
vi CONTENTS Superalgebra Structures on M-(k) in Characteristic 2 . . . 255 C. Baboo-
On Rings Whose Homomorphic Images Are p - I n j e c t i v e . . . 261
C. y. Hong, N. K. Kirn, and Y. Lee
Irreducible Characters for Algebraic Groups in Characteristic
Three. II . . . 273 J . Ye and Z. Zhou
On the Generalized H-Ue Structure of Associative Algebras
in Yetter-Drinfeld Categories . . . 307 S. Wang
Associated Primes of Generalized Local Cohomology M o d u l e s . . . 327 S. Yassemi, L. Khatami, and T. Sharif
Deformation Cohomology for Yetter-DrinfeI'd Modules and
Hopf (Bi)Modules. . . . 331 F. Panaite and D. Sitefan
On Nil Subsemigroups of Rings with Group Identities . . . 347
K. I. Beidar, W.-F. Ke, and C.-H. Liu
Some Diophantine Equations over Z[;] and Z with
Applications to K^ of at Field . . . 353
K. Xu and H. Qin
Symmetry in Algebraic Algebras with Positive Involution. . . . 369 D. R. Far en ic k
Outer Actions of Centralizer Hopf Algebras on Separable
Extensions . . . 383
L. Kadison and D. Nikshych
A Note on Moduli of Inner Ideals in Jordan Systems . . . 411 F. Montaner
Generating and Covering the Alternating or Symmetric Group . . . 425 D. M. Rodgers
On the Dimension of the Irreducible Modules for Semisimple
Hopf Algebras . . . 437 M. D. Staic
Polynomial Identities of M2(G). . . . 443 U. Vishne
CONTENTS vii Locally Dynkin Quivers and Hereditary Coalgebras Whose
Left Comodules Are Direct Sums of Finite Dimensional
C o m o d u l e s . . . 455 S. Nowak and D. Simson
Almost Precovers . . . 477 L. Eicon and B. Torrecillas
Graded Identities of Group Algebras . . . 489 S. K. Sehgal and M. V. Zaicev
Surjectivity of the Ideal Extension Map ( R ) ( R X , X ~1; a]) ... 507 E. A. Whelan
