根据代数扩张的思想介绍丁余代数的扩张,进而引,入双代数和Hopf代数的扩张。证明了有限维余代数的平凡扩张是coFrobenius余代数,给出双代数的扩张成为双代数的一个充要条件和成为Hopf代数的一个充分条件,最后给出一类是biFrobenius代数但不是Hopf代数的例子。
This paper introduces the extension of coalgebra (respectively, bialgebra, Hopf algebra), which is similar to the case of algebra. Proves that the trivial extension of a finite dimensional coalgebra is coFrobenius. A sufficient-necessary (respectively, sufficient) condition is given that the extension of bialgebra is a bialgebra (respectively, Hopf algebra). Finally, a class of biFrobenius algebra is presented which is not Hopf algebra.