Published online by Cambridge University Press: 08 May 2014
Let $X$ be a smooth proper curve over a finite field of characteristic
$p$ . We prove a product formula for
$p$ -adic epsilon factors of arithmetic
$\mathscr{D}$ -modules on
$X$ . In particular we deduce the analogous formula for overconvergent
$F$ -isocrystals, which was conjectured previously. The
$p$ -adic product formula is a counterpart in rigid cohomology of the Deligne–Laumon formula for epsilon factors in
$\ell$ -adic étale cohomology (for
$\ell \neq p$ ). One of the main tools in the proof of this
$p$ -adic formula is a theorem of regular stationary phase for arithmetic
$\mathscr{D}$ -modules that we prove by microlocal techniques.