Diophantine Conditions and Global Properties for Systems of Vector Fields in Tori and Spheres
摘要
In this note, we explore global properties for systems of first-order differential operators, with a focus on zero-order perturbations of constant-coefficient vector fields defined on products of tori and three-dimensional spheres. By analyzing the behavior of the symbol of the system, we establish necessary and sufficient conditions for achieving global hypoellipticity, global analytic hypoellipticity and global solvability.