Title: Nonlinear stability for the Maxwell--Born--Infeld system on a Schwarzschild background,
Abstract: In this paper we prove small data global existence for solutions to the
Maxwell--Born--Infeld (MBI) system on a fixed Schwarzschild background. This
system has appeared in the context of string theory and can be seen as a
nonlinear model problem for the stability of the background metric itself, due
to its tensorial and quasilinear nature. The MBI system models nonlinear
electromagnetism and does not display birefringence. The key element in our
proof lies in the observation that there exists a first-order differential
transformation which brings solutions of the spin $\pm 1$ Teukolsky equations,
satisfied by the extreme components of the field, into solutions of a "good"
equation (the Fackerell--Ipser Equation). This strategy was established in [F.
Pasqualotto, The spin $\pm 1$ Teukolsky equations and the Maxwell system on
Schwarzschild, Preprint 2016, arXiv:1612.07244] for the linear Maxwell field on
Schwarzschild. We show that analogous Fackerell--Ipser equations hold for the
MBI system on a fixed Schwarzschild background, which are however nonlinearly
coupled. To essentially decouple these right hand sides, we setup a bootstrap
argument. We use the $r^p$ method of Dafermos and Rodnianski in [M. Dafermos
and I. Rodnianski, A new physical-space approach to decay for the wave equation
with applications to black hole spacetimes, in XVIth International Congress on
Mathematical Physics, Pavel Exner ed., Prague 2009 pp. 421-433, 2009,
arXiv:0910.4957] in order to deduce decay of some null components, and we infer
decay for the remaining quantities by integrating the MBI system as transport
equations.