  Given a torus action on a compact space X, a fundamental result of Borel and
Atiyah-Segal asserts that the equivariant cohomology of X is concentrated in
the fixed locus X^T, up to inverting enough Chern classes. We prove an analogue
for algebraic varieties over an arbitrary field. In fact, we deduce this from a
categorification at the level of equivariant derived categories and even
equivariant stable motivic homotopy categories, which also gives concentration
at the level of Voevodsky motives and for homotopy K-theory.
