3 papers
math.NT2026
The Hurwitz sum-of-squares problem depends on the base field
Chi Zhang, Haoran Zhu
We show that the Hurwitz problem for sums of squares can depend on the base field. More precisely, we construct an explicit formula of type over every field of charact…
math.RA2025
Sweedler duality for Hom-(co)algebras and Hom-(co)modules
Jiacheng Sun, Shuanhong Wang, Chi Zhang +1
We establish a dual version of infinite-dimensional Hom-algebras and Hom-modules by using the Sweedler duality construction. Additionally, linear morphisms between infinite-dimensi…
math.RT2025
Kronecker coefficients and Harrison centres of the representation ring of the symmetric group
Jia-Cheng Sun, Chi Zhang, Haoran Zhu
We present a computational approach to studying the structure of the representation ring of the symmetric group in dimension six. The Kronecker coefficients and all power formulae…