Brauer relations, isogenies and parities of ranks

Abstract: The present paper illustrates the utility of Brauer relations, Galois covers of curves and the theory of regulator constants in the context of studying isogenies between Jacobians and their relevance to the parity conjecture. This framework presents a unified approach, enabling the reconstruction of a diverse array of classical isogenies and the derivation of local expressions for Selmer rank parities, drawing from an extensive body of existing literature. These include the local expressions found in the works of Mazur--Rubin (dihedral extensions), Coates--Fukaya--Kato--Sujatha ($p^g$ isogenies), Kramer--Tunnell (quadratic twists of elliptic curves), Dokchitser--Maistret (Richelot isogenies), and Docking (prym construction).