Weil restriction, normal bundles and motivic Thom spaces

Abstract

Recent developments in motivic homotopy theory, particularly the construction of norm functors by Bachmann and Hoyois, have revealed deep connections between algebraic geometry and homotopy-theoretic structures. In this paper, we investigate certain geometric aspects of norm functors through the Weil restriction of schemes, which underlies these constructions. We show that Weil restriction preserves vector bundles and extend existing results concerning normal bundles. We then relate the Weil restriction to norm functors and, using a result of Bachmann and Hoyois, establish its compatibility with motivic Thom spaces. Finally, in the setting of motivic cohomology with rational coefficients, we prove that the Weil restriction map agrees with the norm map induced by a norm functor and that it preserves Thom classes.

Author list updated by mutual agreement. The manuscript has been substantially revised; an incorrect construction in the previous version has been replaced and several proofs have been rewritten