Euler systems for $\mathrm{GSp}(4)$ over imaginary quadratic fields

Abstract

We construct an Euler system attached to general-type cohomological cuspidal automorphic representations of $\mathrm{GSp}(4)$ twisted by a Groessencharacter of an imaginary quadratic field. We then use this to bound strict Selmer groups under standard hypotheses. In addition, our approach gives a way of extending the $\mathrm{GSp}(4)\times\mathrm{GL}(2)$ Euler system of Hsu-Jin-Sakamoto to a motivic statement which also covers certain small weights omitted in op$.$cit.