We investigate existence and nonexistence of action ground states and nodal
action ground states for the nonlinear Schrödinger equation on noncompact
metric graphs with mixed homogeneous Kirchhoff and Dirichlet boundary
conditions. We first obtain abstract sufficient conditions for existence, typical of
problems with lack of compactness, in terms of “levels at infinity” for the
action functional associated with the problems. Then we analyze in detail
two relevant classes of graphs. For noncompact graphs with at least one
half-line, we detect purely topological sharp conditions preventing the existence
of ground states or of nodal ground states. We also investigate analogous
conditions of metrical nature. The negative results are complemented by several
sufficient conditions to ensure existence, either of topological or metrical
nature, or a combination of the two. For graphs with infinitely many edges,
all bounded, we focus on periodic graphs and infinite trees. In these cases,
our results completely describe the phenomenology. Furthermore, we study
nodal domains and nodal sets of nodal ground states and we show that
the situation on graphs can be totally different from that on domains of
.
Keywords
nonlinear Schrödinger, ground states, nodal solutions,
least action, constrained minimization
Université Polytechnique
Hauts-de-France
INSA Hauts-de-France
CERAMATHS - Laboratoire de Matériaux Céramiques et de
Mathématiques
F-59313 Valenciennes
France
Département de Mathématiques
Université de Mons
Mons
Belgium
Université Polytechnique
Hauts-de-France
INSA Hauts-de-France
CERAMATHS - Laboratoire de Matériaux Céramiques et de
Mathématiques
F-59313 Valenciennes
France
Department of Mathematics
Brown University
Providence, RI
United States
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