Abstract:
This paper proves the existence of small-amplitude globalin-time unique mild solutions to both the Landau equation including
the Coulomb potential and the Boltzmann equation without angular
cutoff. Since the well-known works (Guo, 2002) and (Gressman-Strain2011, AMUXY-2012) on the construction of classical solutions in smooth
Sobolev spaces which in particular are regular in the spatial variables,
has still remained an open problem to obtain global solutions in an $L^\infty_{x,v}$
framework, similar to that in (Guo-2010), for the Boltzmann equation
with cutoff in general bounded domains. One main difficulty arises
from the interaction between the transport operator and the velocitydiffusion-type collision operator in the non-cutoff Boltzmann and Landau equations; another major difficulty is the potential formation of
singularities for solutions to the boundary value problem. In this work
we introduce a new function space with low regularity in the spatial
variable to treat the problem in cases when the spatial domain is either
a torus, or a finite channel with boundary. For the latter case, either the
inflow boundary condition or the specular reflection boundary condition
is considered. An important property of the function space is that the
$L^\infty_T L^2_{v}$ norm, in velocity and time, of the distribution function is in the
Wiener algebra$A(\Omega)$ in the spatial variables. Besides the construction
of global solutions in these function spaces, we additionally study the
large-time behavior of solutions for both hard and soft potentials, and
we further justify the property of propagation of regularity of solutions
in the spatial variables. To the best of our knowledge these results
may be the first ones to provide an elementary understanding of the
existence theories for the Landau or non-cutoff Boltzmann equations in
the situation where the spatial domain has a physical boundary.
This is a joint work with Renjun Duan (The Chinese University of
Hong Kong), Shuangqian Liu (Jinan University) and Shota Sakamoto
(Tohoku University). |