Tóm tắt: In characteristic $0$, it is known that cyclic extensions of fields are determined by Kummer theory. In characteristic $p$, in addition to Kummer theory, we need Artin–Schreier–Witt theory to classify these extensions. Matsuda constructed a formal morphism that connects these two theories, providing a bridge between characteristic $p$ and characteristic $0$. In this talk, we discuss an algebraization process of Matsuda’s theory to study the lifting of abelian isogenies from characteristic $p$ to characteristic $0$ and show that every lift of an abelian étale cover of a local scheme is a pull-back of such a lift of an abelian isogeny.
Đỗ Minh Thắng,
Sonja Hannibal,
Arnulf Jentzen,
Non-convergence to global minimizers in data driven supervised deep learning: Adam and stochastic gradient descent optimization provably fail to converge to global minimizers in the training of deep neural networks with ReLU activation,
Journal of Mathematical Analysis and Applications, 564 (2026) 130724