Résumé : We show that over any uncountable field of characteristic different from two, a very general hypersurface of dimension $n > 2$ and degree at least $log_2 (n) + 2$ is not stably rational. This significantly improves earlier results of Kollár and Totaro. As a byproduct of our proof, we obtain new counterexamples to the integral Hodge conjecture, answering a question of Voisin and Colliot-Thélène – Voisin.

Mots-Clés : hypersurfaces; rationality problem; stable rationality; integral Hodge conjecture; unramified cohomology