# Reference - motives of curves

There is a really interesting comment in this question that I was unable to find a reference...

Under the "Tate conjectures, then every motive belongs to the tensor category generated by motives of curves."

This phenomenon is specific to the fields $$\mathbb F_q$$ (in this case you need the Artin motives as well) and $$\bar{\mathbb F}_q$$. Roughly, the outline is as follows.
If the Tate conjecture is true and the Frobenius action is semisimple, then the homological standard conjecture is true. Then Jannsen's Motives, numerical equivalence, and semi-simplicity implies that the category of motives with homological equivalence is semisimple. Moreover, the Tate conjecture gives a description of the simple objects in terms of the characteristic polynomial of Frobenius. Then Honda–Tate theory constructs all such characteristic polynomials inside the cohomology of an abelian variety. These are always dominated by Jacobians, so all desired Frobenius eigenvalues occur in the $$H^1$$ of a curve.
Remark. As I understand it, the same is not expected to hold over basically any other type of field. For example, it should be "easy" to write down a Hodge structure that is not in the full abelian tensor subcategory generated by the Hodge structures of weight $$1$$.