John Christian Ottem (UiO) – Very general quartic sixfolds are not stably rational

We prove that a very general quartic sixfold admits no decomposition of the diagonal, and in particular is not stably rational. The proof uses specialization to an explicit quartic sixfold birational to a quadric bundle of the type considered by Colliot-Thélène and Ojanguren. We also prove stable irrationality for very general six-dimensional intersections of four quadrics.