1,831 research outputs found
A dimension-breaking phenomenon for water waves with weak surface tension
It is well known that the water-wave problem with weak surface tension has
small-amplitude line solitary-wave solutions which to leading order are
described by the nonlinear Schr\"odinger equation. The present paper contains
an existence theory for three-dimensional periodically modulated solitary-wave
solutions which have a solitary-wave profile in the direction of propagation
and are periodic in the transverse direction; they emanate from the line
solitary waves in a dimension-breaking bifurcation. In addition, it is shown
that the line solitary waves are linearly unstable to long-wavelength
transverse perturbations. The key to these results is a formulation of the
water wave problem as an evolutionary system in which the transverse horizontal
variable plays the role of time, a careful study of the purely imaginary
spectrum of the operator obtained by linearising the evolutionary system at a
line solitary wave, and an application of an infinite-dimensional version of
the classical Lyapunov centre theorem.Comment: The final publication is available at Springer via
http://dx.doi.org/10.1007/s00205-015-0941-
Two-parameter nonsmooth grazing bifurcations of limit cycles: classification and open problems
This paper proposes a strategy for the classification of codimension-two grazing bifurcations of limit cycles in piecewise smooth systems of ordinary differential equations. Such nonsmooth transitions (C-bifurcations) occur when the cycle interacts with a discontinuity boundary of phase space in a non-generic way. Several such codimension-one events have recently been identified, causing for example period-adding or sudden onset of chaos. Here, the focus is on codimension-two grazings that are local in the sense that the dynamics can be fully described by an appropriate PoincarƩ map from a neighbourhood of the grazing point (or points) of the critical cycle to itself. It is proposed that codimension-two grazing bifurcations can be divided into three distinct types: either the grazing point is degenerate, or the the grazing cycle is itself degenerate (e.g. non-hyperbolic) or we have the simultaneous occurrence of two grazing events. A careful distinction is drawn between their occurrence in systems with discontinuous states, discontinuous vector fields, or that have discontinuity in some derivative of the vector field. Examples of each kind of bifurcation are presented, mostly derived from mechanical applications. For each example, where possible, principal bifurcation curves characteristic to the codimension-two scenario are presented and general features of the dynamics discussed. Many avenues for future research are opened.
Bifurcation of Fredholm Maps I; The Index Bundle and Bifurcation
We associate to a parametrized family of nonlinear Fredholm maps
possessing a trivial branch of zeroes an {\it index of bifurcation}
which provides an algebraic measure for the number of bifurcation points from
the trivial branch. The index is derived from the index bundle of
the linearization of the family along the trivial branch by means of the
generalized -homomorphism. Using the Agranovich reduction and a
cohomological form of the Atiyah-Singer family index theorem, due to Fedosov,
we compute the bifurcation index of a multiparameter family of nonlinear
elliptic boundary value problems from the principal symbol of the linearization
along the trivial branch. In this way we obtain criteria for bifurcation of
solutions of nonlinear elliptic equations which cannot be achieved using the
classical Lyapunov-Schmidt method.Comment: 42 pages. Changes: added Lemma 2.31 and a reference + minor
corrections. To appear on TMN
Probability of local bifurcation type from a fixed point: A random matrix perspective
Results regarding probable bifurcations from fixed points are presented in
the context of general dynamical systems (real, random matrices), time-delay
dynamical systems (companion matrices), and a set of mappings known for their
properties as universal approximators (neural networks). The eigenvalue spectra
is considered both numerically and analytically using previous work of Edelman
et. al. Based upon the numerical evidence, various conjectures are presented.
The conclusion is that in many circumstances, most bifurcations from fixed
points of large dynamical systems will be due to complex eigenvalues.
Nevertheless, surprising situations are presented for which the aforementioned
conclusion is not general, e.g. real random matrices with Gaussian elements
with a large positive mean and finite variance.Comment: 21 pages, 19 figure
Parity and generalized multiplicity
Assuming that X and Y are Banach spaces and that T is a path of linear Fredholm operators with invertible endpoints, in [F-Pl] we defined a homotopy invariant "the parity of T . The parity plays a fundamental role in bifurcation problems, and in degree theory for nonlinear Fredholm-type mappings. Here we prove that, generically, the parity is a mod 2 count of the number of transversal intersections of T with the set of singular operators, that at an isolated singular point of x of T the local parity remains invariant under Lyapunov-Schmidt reduction, and that it coincides with the mod 2 reduction of any one of the various concepts of generalized multiplicity which have been defined in the context of linearized bifurcation data
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