Crystals and Chern classes

The goal of this paper is to study the Chern classes of coherent sheaves (and more generally perfect complexes) that admit crystal structures in the setting of crystalline cohomology and more generally relative prismatic cohomology. In the former theory, we show that the Chern classes vanish on the nose; in the latter theory, we show the classes are torsion with uniformly bounded exponents determined by suitable Bernoulli numbers. We also formulate some questions about syntomic Chern classes of such sheaves.