The existence of the well-known Jacquet–Langlands correspondence was established by
Jacquet and Langlands via the trace formula method in 1970. An explicit construction
of such a correspondence was obtained by Shimizu via theta series in 1972. In
this paper, we extend the automorphic descent method of Ginzburg–Rallis–Soudry
to a new setting. As a consequence, we recover the classical Jacquet–Langlands correspondence
for PGL(2) via a new explicit construction.
Motivated by the work of Candelas, de la Ossa and Rodriguez-Villegas , we study the relations between Hasse-Witt matrices and period integrals of Calabi-Yau hypersurfaces in both toric varieties and partial flag varieties. We prove a conjecture by Vlasenko  on higher Hasse-Witt matrices for toric hypersurfaces following Katz's method of local expansion [14, 15]. The higher Hasse-Witt matrices also have close relation with period integrals. The proof gives a way to pass from Katz's congruence relations in terms of expansion coefficients  to Dwork's congruence relations  about periods.