Simple factor dressing and the López–Ros deformation of minimal surfaces in Euclidean 3-space

The aim of this paper is to investigate a new link between integrable systems and minimal surface theory. The dressing operation uses the associated family of flat connections of a harmonic map to construct new harmonic maps. Since a minimal surface in 3-space is a Willmore surface, its conformal Gauss map is harmonic and a dressing on the conformal Gauss map can be defined. We study the induced transformation on minimal surfaces in the simplest case, the simple factor dressing, and show that the well-known López–Ros deformation of minimal surfaces is a special case of this transformation. We express the simple factor dressing and the López–Ros deformation explicitly in terms of the minimal surface and its conjugate surface. In particular, we can control periods and end behaviour of the simple factor dressing. This allows to construct new examples of doubly-periodic minimal surfaces arising as simple factor dressings of Scherk’s first surface.

     

A note on subdifferentials of pointwise suprema

The paper suggests a new approach to calculation of subdifferentials of suprema of convex functions without any qualification conditions which essentially relies on the Hirriart-Urruty–Phelps formula for subdifferentials of sums of convex l.s.c. functions (also supplied with a simple new proof). The approach in particular provides for a simpler way to (a certain generalization of) the most recent and so far most general formulas of Hantoute–López–Zalinescu and López–Volle.     

Convergence of Padé approximants of Stieltjes-type meromorphic functions and the relative asymptotics of orthogonal polynomials on the real line

We obtain results on the convergence of Padé approximants of Stieltjes-type meromorphic functions and the relative asymptotics of orthogonal polynomials on unbounded intervals. These theorems extend some results given by Guillermo López in this direction substituting the Carleman condition in his theorems by the determination of the corresponding moment problem.     

New Formulas for the Fenchel Subdifferential of the Conjugate Function

Following (López and Volle, J Convex Anal 17, 2010) we provide new formulas for the Fenchel subdifferential of the conjugate of functions defined on locally convex spaces. In particular, this allows deriving expressions for the minimizers set of the lower semicontinuous convex hull of such functions. These formulas are written by means of primal objects related to the subdifferential of the initial function, namely a new enlargement of the Fenchel subdifferential operator.     

On the convergence analysis of the gradient-CQ algorithms for the split feasibility problem

Numerical Algorithms - In this work, based on the gradient method and the relaxed CQ algorithm introduced by López et al. (Inverse Probl. 28, 085004, 2012), we introduce two gradient-CQ...     

Outer limits of subdifferentials for min–max type functions

Abstract

We generalize the outer subdifferential construction suggested by Cánovas, Henrion, López and Parra for max type functions to pointwise minima of regular Lipschitz functions. We also answer an open question about the relation between the outer subdifferential of the support of a regular function and the end set of its subdifferential posed by Li, Meng and Yang.     

Minimizability of developable Riemannian foliations

Let (M,F){(M,\mathcal{F})} be a closed manifold with a Riemannian foliation. We show that the secondary characteristic classes of the Molino’s commuting sheaf of (M,F){(M,\mathcal{F})} vanish if (M,F){(M,\mathcal{F})} is developable and π ₁ M is of polynomial growth. By theorems of álvarez López in (álvarez López, Ann. Global Anal. Geom., 10:179–194, 1992) and (álvarez López, Ann. Pol. Math., 64:253–265, 1996), our result implies that (M,F){(M,\mathcal{F})} is minimizable under the same conditions. As a corollary, we show that (M,F){(M,\mathcal{F})} is minimizable if F{\mathcal{F}} is of codimension 2 and π ₁ M is of polynomial growth.     

Jump tail dependence in Lévy copula models

This paper investigates the dependence of extreme jumps in multivariate Lévy processes. We introduce a measure called jump tail dependence, defined as the probability of observing a large jump in one component of a process given a concurrent large jump in another component. We show that this measure is determined by the Lévy copula alone and that it is independent of marginal Lévy processes. We derive a consistent nonparametric estimator for jump tail dependence and establish its asymptotic distribution. Regarding the economic relevance of the measure, a simulation study illustrates that jump tail dependence has a substantial impact on financial portfolio distributions and optimal portfolio weights.     

A Note on the Paper “Linear Complementarity Problems Over Symmetric Cones: Characterization of Qb-Transformations and Existence Results”

In this note, we correct a mistake in the paper (López et al., J Optim Theory Appl 159(3):741–768, 2013).     

Non-Kähler manifolds and GIT-quotients

Bosio generalized the construction by López de Medrano-Verjovsky- Meersseman (LVM) of a family of non-algebraic compact complex manifolds of any dimension. We describe how to construct the generalized family from certain Geometric Invariant Theory (GIT) quotients. We show that Bosio’s generalization parallels exactly the extension from Mumford’s GIT to the more general GIT developed by Białynicki-Birula and Świȩcicka. This point of view yields new results on the geometry of LVM and Bosio’s manifolds.     

Birth of attracting compact invariant submanifolds diffeomorphic to moment-angle manifolds in generic families of dynamics

All the compact intersections of quadrics known as moment-angle manifolds appear as attractors in generalized Hopf bifurcations. To cite this article: M. Chaperon, S. López De Medrano, C. R. Acad. Sci. Paris, Ser. I 346 (2008).     

Homogeneous quaternionic Kähler structures of linear type

A classification of homogeneous quaternionic Kähler structures by real tensors is given and related to Fino's representation theoretic decomposition. A relationship between the modules whose dimension grows linearly and quaternionic hyperbolic space is found. To cite this article: M. Castrillón López et al., C. R. Acad. Sci. Paris, Ser. I 338 (2004).     

The sand-pile model and Tutte polynomials

A new explicit bijection between spanning trees and recurrent configurations of the sand-pile model is given. This mapping is such that the difference between the number of grains on a configuration and the external activity of the associate tree is the number of edges of the graph. It gives a bijective proof of a result of Merino López expressing the generating function of recurrent configurations as an evaluation of the Tutte polynomial.     

Stationarity and Regularity of Infinite Collections of Sets. Applications to Infinitely Constrained Optimization

This article continues the investigation of stationarity and regularity properties of infinite collections of sets in a Banach space started in Kruger and López (J.?Optim. Theory Appl. 154(2), 2012), and is mainly focused on the application of the stationarity criteria to infinitely constrained optimization problems. We consider several settings of optimization problems which involve (explicitly or implicitly) infinite collections of sets and deduce for them necessary conditions characterizing stationarity in terms of dual space elements??normals and/or subdifferentials.     

On the Hopf bifurcation for flows

Under fairly general hypotheses, we prove the existence of the families of periodic orbits obtained by Hopf bifurcation, with emphasis on their smoothness. A Banach version of a theorem of Lyapounov is obtained as a corollary. The proofs are complete, simple and original. To cite this article: M. Chaperon, S. López de Medrano, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

A primal–dual operation on sets linked with closed convex relaxation processes

We give some properties and uses of a primal–dual operation on sets that appear in the closed convex relaxation process (Hiriart-Urruty et al. in Rev. Mat. Iberoam. 27(2):449–474, 2011; López and Volle in J. Conv. Anal. 17(3–4):1057–1075, 2010). Applications are provided concerning a class of relaxed minimization problems in the frame of the so called B-regularization theory. Special attention is paid to the case when the initial problem admits optimal solutions under compactness assumptions.     

On the area of constant mean curvature discs and annuli with circular boundaries

It is still an open question whether a constant mean curvature (CMC) disc which is bounded by a circle is necessarily a spherical cap or a flat disc. The authors together with López [1] recently showed that the only stable CMC discs which are bounded by a circle are spherical caps. In this paper we derive lower bounds for the area of constant mean curvature discs and annuli with circular boundaries in 3-dimensional space forms. Received November 8, 1999; in final form January 18, 2000 / Published online March 12, 2001     

Halpern Iteration in CAT（k） Spaces

In this paper we show that an iterative sequence generated by the Halpern algorithm converges to a fixed point in the case of complete CAT(κ) spaces. Similar results for Hadamard manifolds were obtained in [Li, C., López, G., Martín-Márquez, V.: Iterative algorithms for nonexpansive mappings on Hadamard manifolds. Taiwanese J. Math., 14, 541–559 (2010)], but we study a much more general case. Moreover, we discuss the Halpern iteration procedure for set-valued mappings.     

Generalized hypergeometric,digamma and trigamma distributions

Summary In this paper we introduce and study new probability distributions named “digamma” and “trigamma” defined on the set of all positive integers. They are obtained as limits of the zero-truncated Type B3 generalized hypergeometric distributions (inverse Pólya-Eggenberger or negative binomial beta distributions), and also by compounding the logarithmic series distributions. The family of digamma distributions has the logarithmic series as a limit and the trigamma as another limit. The trigamma distributions are very close to the zeta (Zipf) distributions. Thus, our new distributions are useful as substitutes of the logarithmic series when the observed frequency data have such a long tail that cannot be fitted by the latter distributions. In the beginning sections we summarize properties of the Type B3 generalized hypergeometric distributions. It is emphasized that the distributions are obtained by compounding a Poisson distribution by “gamma product-ratio” distributions.     

Generalized viscosity implicit rules for solving quasi-inclusion problems of accretive operators in Banach spaces

The generalized viscosity implicit rules for solving quasi-inclusion problems of accretive operators in Banach spaces are established. The strong convergence theorems of the rules to a solution of quasi-inclusion problems of accretive operators are proved under certain assumptions imposed on the sequences of parameters. The results presented in this paper extend and improve the main results of Refs. (Moudafi, J Math Anal Appl. 2000;241:46–55; Xu et al., Fixed Point Theory Appl. 2015;2015:41; López et al., Abstr Appl Anal. 2012;2012; Cholamjiak, Numer Algor. DOI:10.1007/s11075-015-0030-6.). Moreover, some applications to monotone variational inequalities, convex minimization problem and convexly constrained linear inverse problem are presented.