1,678 research outputs found
Global behaviour of radially symmetric solutions stable at infinity for gradient systems
This paper is concerned with radially symmetric solutions of systems of the
form where space variable and and
state-parameter are multidimensional, and the potential is coercive at
infinity. For such systems, under generic assumptions on the potential, the
asymptotic behaviour of solutions "stable at infinity", that is approaching a
spatially homogeneous equilibrium when approaches , is
investigated. It is proved that every such solutions approaches a stacked
family of radially symmetric bistable fronts travelling to infinity. This
behaviour is similar to the one of bistable solutions for gradient systems in
one unbounded spatial dimension, described in a companion paper. It is expected
(but unfortunately not proved at this stage) that behind these travelling
fronts the solution again behaves as in the one-dimensional case (that is, the
time derivative approaches zero and the solution approaches a pattern of
stationary solutions).Comment: 52 pages, 14 figures. arXiv admin note: substantial text overlap with
arXiv:1703.01221. text overlap with arXiv:1604.0200
Radial terrace solutions and propagation profile of multistable reaction-diffusion equations over
We study the propagation profile of the solution to the nonlinear
diffusion problem ,
, where is of multistable type:
, , , where is a positive constant, and
may have finitely many nondegenerate zeros in the interval . The class
of initial functions includes in particular those which are nonnegative
and decay to 0 at infinity. We show that, if converges to as
in , then the long-time dynamical
behavior of is determined by the one dimensional propagating terraces
introduced by Ducrot, Giletti and Matano [DGM]. For example, we will show that
in such a case, in any given direction , converges to a pair of one dimensional propagating terraces, one moving in
the direction of , and the other is its reflection moving in the
opposite direction .
Our approach relies on the introduction of the notion "radial terrace
solution", by which we mean a special solution of such that, as , converges to the corresponding one
dimensional propagating terrace of [DGM]. We show that such radial terrace
solutions exist in our setting, and the general solution can be well
approximated by a suitablly shifted radial terrace solution . These
will enable us to obtain better convergence result for .
We stress that is a high dimensional solution without any symmetry.
Our results indicate that the one dimensional propagating terrace is a rather
fundamental concept; it provides the basic structure and ingredients for the
long-time profile of solutions in all space dimensions
Comprehensive Border Bases for Zero Dimensional Parametric Polynomial Ideals
In this paper, we extend the idea of comprehensive Gr\"{o}bner bases given by
Weispfenning (1992) to border bases for zero dimensional parametric polynomial
ideals. For this, we introduce a notion of comprehensive border bases and
border system, and prove their existence even in the cases where they do not
correspond to any term order. We further present algorithms to compute
comprehensive border bases and border system. Finally, we study the relation
between comprehensive Gr\"{o}bner bases and comprehensive border bases w.r.t. a
term order and give an algorithm to compute such comprehensive border bases
from comprehensive Gr\"{o}bner bases.Comment: 15 pages, 8 sections and 3 algorithm
Global relaxation of bistable solutions for gradient systems in one unbounded spatial dimension
This paper is concerned with spatially extended gradient systems of the form
where spatial domain is the
whole real line, state-parameter is multidimensional, denotes
a fixed diffusion matrix, and the potential is coercive at infinity.
"Bistable" solutions, that is solutions close at both ends of space to stable
homogeneous equilibria, are considered. For a solution of this kind, it is
proved that, if the homogeneous equilibria approached at both ends belong to
the same level set of the potential and if an appropriate (localized in space)
energy remains bounded from below when time increases, then the solution
approaches, when time approaches infinity, a pattern of stationary solutions
homoclinic or heteroclinic to homogeneous equilibria. This result provides a
step towards a complete description of the global behaviour of all bistable
solutions that is pursued in a companion paper. Some consequences are derived,
and applications to some examples are given.Comment: 69 pages, 15 figure
Local existence and uniqueness in the largest critical space for a surface growth model
We show the existence and uniqueness of solutions (either local or global for
small data) for an equation arising in different aspects of surface growth.
Following the work of Koch and Tataru we consider spaces critical with respect
to scaling and we prove our results in the largest possible critical space such
that weak solutions are defined. The uniqueness of global weak solutions
remains unfortunately open, unless the initial conditions are sufficiently
small.Comment: 17 page
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