  Exactly solvable mirror pairs of Calabi-Yau threefolds of hypersurface type
exist in the class of Gepner models that include nondiagonal affine invariants.
Motivated by the string modular interpretation established previously for
models in this class it is natural to ask whether the arithmetic structure of
mirror pairs of varieties reflects the fact that as conformal field theories
they are isomorphic. Mirror symmetry in particular predicts that the
L-functions of the \Omega-motives of such pairs are identical. In the present
paper this prediction is confirmed by showing that the \Omega-motives of
exactly solvable mirror pairs are isomorphic. This follows as a corollary from
a more general result establishing an isomorphism between nondiagonally and
diagonally induced motives in this class of varieties. The motivic approach
formulated here circumvents the difficulty that no mirror construction of the
Hasse-Weil zeta function is known.
