383 research outputs found
Activity Identification and Local Linear Convergence of Douglas--Rachford/ADMM under Partial Smoothness
Convex optimization has become ubiquitous in most quantitative disciplines of
science, including variational image processing. Proximal splitting algorithms
are becoming popular to solve such structured convex optimization problems.
Within this class of algorithms, Douglas--Rachford (DR) and alternating
direction method of multipliers (ADMM) are designed to minimize the sum of two
proper lower semi-continuous convex functions whose proximity operators are
easy to compute. The goal of this work is to understand the local convergence
behaviour of DR (resp. ADMM) when the involved functions (resp. their
Legendre-Fenchel conjugates) are moreover partly smooth. More precisely, when
both of the two functions (resp. their conjugates) are partly smooth relative
to their respective manifolds, we show that DR (resp. ADMM) identifies these
manifolds in finite time. Moreover, when these manifolds are affine or linear,
we prove that DR/ADMM is locally linearly convergent. When and are
locally polyhedral, we show that the optimal convergence radius is given in
terms of the cosine of the Friedrichs angle between the tangent spaces of the
identified manifolds. This is illustrated by several concrete examples and
supported by numerical experiments.Comment: 17 pages, 1 figure, published in the proceedings of the Fifth
International Conference on Scale Space and Variational Methods in Computer
Visio
Constant-angle surfaces in liquid crystals
We discuss some properties of surfaces in R3 whose unit normal has constant angle with an assigned direction field. The constant angle condition can be rewritten as an Hamilton-Jacobi equation correlating the surface and the direction field. We focus on examples motivated by the physics of interfaces in liquid crystals and of layered fluids, and discuss the properties of the constant-angle surfaces when the direction field is singular along a line (disclination) or at a point (hedgehog defect
On the dynamics of WKB wave functions whose phase are weak KAM solutions of H-J equation
In the framework of toroidal Pseudodifferential operators on the flat torus
we begin by proving the closure under
composition for the class of Weyl operators with
simbols . Subsequently, we
consider when where and we exhibit the toroidal version of the
equation for the Wigner transform of the solution of the Schr\"odinger
equation. Moreover, we prove the convergence (in a weak sense) of the Wigner
transform of the solution of the Schr\"odinger equation to the solution of the
Liouville equation on written in the measure sense.
These results are applied to the study of some WKB type wave functions in the
Sobolev space with phase functions in the class
of Lipschitz continuous weak KAM solutions (of positive and negative type) of
the Hamilton-Jacobi equation for with , and to the study of the
backward and forward time propagation of the related Wigner measures supported
on the graph of
Wong-Zakai approximation of solutions to reflecting stochastic differential equations on domains in Euclidean spaces II
The strong convergence of Wong-Zakai approximations of the solution to the
reflecting stochastic differential equations was studied in [2]. We continue
the study and prove the strong convergence under weaker assumptions on the
domain.Comment: To appear in "Stochastic Analysis and Applications 2014-In Honour of
Terry Lyons", Springer Proceedings in Mathematics and Statistic
Weighted Sobolev spaces of radially symmetric functions
We prove dilation invariant inequalities involving radial functions,
poliharmonic operators and weights that are powers of the distance from the
origin. Then we discuss the existence of extremals and in some cases we compute
the best constants.Comment: 38 page
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