Nonlinear response and discrete breather excitation in driven micro-mechanical cantilever arrays

We explain the origin of the generation of discrete breathers (DBs) in experiments on damped and driven micromechanical cantilever arrays (M.Sato et al. Phys. Rev. Lett. {\bf 90}, 044102, 2003). Using the concept of the nonlinear response manifold (NLRM) we provide a systematic way to find the optimal parameter regime in damped and driven lattices where DBs exist. Our results show that DBs appear via a new instability of the NLRM different from the anticipated modulational instability (MI) known for conservative systems. We present several ways of exciting DBs, and compare also to experimental studies of exciting and destroying DBs in antiferromagnetic layered systems.Comment: 4 pages, 5 figure

Driven Intrinsic Localized Modes in a Coupled Pendulum Array

Intrinsic localized modes (ILMs), also called discrete breathers, are directly generated via modulational instability in an array of coupled pendulums. These ILMs can be stabilized over a range of driver frequencies and amplitudes. They are characterized by a pi-phase difference between their center and wings. At higher driver frequencies, these ILMs are observed to disintegrate via a pulsating instability, and the mechanism of this breather instability is investigated.Comment: 5 pages, 6 figure

"El pez de oro", de Gamaliel Churata, en la tradición de la literatura peruana

Este trabajo pretende ser una reflexión sobre la obra poco conocida de Gamaliel Churata (Arequipa, 1897-Lima, 1969), especialmente sobre El Pez de Oro (1957), que para algunos es «la Biblia del indigenismo» y para otros «uno de los grandes retos no asumidos de la crítica peruana», si bien el reto se está asumiendo en los últimos años en una serie de trabajos críticos que mencionamos a lo largo de estas páginas. Para evaluar esta obra, hay que observar la evolución de Churata desde la época del Boletín Titikaka (1926-30), órgano difusor del movimiento Orkopata que él mismo dirige desde 1925, hasta la publicación de El Pez de Oro en 1957. Este movimiento ha sido objeto de varios estudios, el más completo de los cuales es el de Vich; pero es necesario distinguir a partir de él la evolución de un proyecto literario que se plasma en El Pez de Oro y que gira sobre uno de los ejes más importantes de la literatura peruana, la heterogeneidad de sus materiales literario

Strain-induced interface reconstruction in epitaxial heterostructures

We investigate in the framework of Landau theory the distortion of the strain fields at the interface of two dissimilar ferroelastic oxides that undergo a structural cubic-to-tetragonal phase transition. Simple analytical solutions are derived for the dilatational and the order parameter strains that are globally valid over the whole of the heterostructure. The solutions reveal that the dilatational strain exhibits compression close to the interface which may in turn affect the electronic properties in that region.Comment: 7 pages, 5 figures, to be published in Physical Review

DivClust: Controlling Diversity in Deep Clustering

Clustering has been a major research topic in the field of machine learning, one to which Deep Learning has recently been applied with significant success. However, an aspect of clustering that is not addressed by existing deep clustering methods, is that of efficiently producing multiple, diverse partitionings for a given dataset. This is particularly important, as a diverse set of base clusterings are necessary for consensus clustering, which has been found to produce better and more robust results than relying on a single clustering. To address this gap, we propose DivClust, a diversity controlling loss that can be incorporated into existing deep clustering frameworks to produce multiple clusterings with the desired degree of diversity. We conduct experiments with multiple datasets and deep clustering frameworks and show that: a) our method effectively controls diversity across frameworks and datasets with very small additional computational cost, b) the sets of clusterings learned by DivClust include solutions that significantly outperform single-clustering baselines, and c) using an off-the-shelf consensus clustering algorithm, DivClust produces consensus clustering solutions that consistently outperform single-clustering baselines, effectively improving the performance of the base deep clustering framework.Comment: Accepted for publication in CVPR 202

q-Symmetries in DNLS-AL chains and exact solutions of quantum dimers

Dynamical symmetries of Hamiltonians quantized models of discrete non-linear Schroedinger chain (DNLS) and of Ablowitz-Ladik chain (AL) are studied. It is shown that for $n$-sites the dynamical algebra of DNLS Hamilton operator is given by the $su(n)$ algebra, while the respective symmetry for the AL case is the quantum algebra su_q(n). The q-deformation of the dynamical symmetry in the AL model is due to the non-canonical oscillator-like structure of the raising and lowering operators at each site. Invariants of motions are found in terms of Casimir central elements of su(n) and su_q(n) algebra generators, for the DNLS and QAL cases respectively. Utilizing the representation theory of the symmetry algebras we specialize to the $n=2$ quantum dimer case and formulate the eigenvalue problem of each dimer as a non-linear (q)-spin model. Analytic investigations of the ensuing three-term non-linear recurrence relations are carried out and the respective orthonormal and complete eigenvector bases are determined. The quantum manifestation of the classical self-trapping in the QDNLS-dimer and its absence in the QAL-dimer, is analysed by studying the asymptotic attraction and repulsion respectively, of the energy levels versus the strength of non-linearity. Our treatment predicts for the QDNLS-dimer, a phase-transition like behaviour in the rate of change of the logarithm of eigenenergy differences, for values of the non-linearity parameter near the classical bifurcation point.Comment: Latex, 19pp, 4 figures. Submitted for publicatio

One swallow doesn’t make a summer: reply to Kataria

In this paper we reply to Mitesh Kataria’s comment, which criticized the simulations of Maniadis, Tufano, and List (2014, Am. Econ. Rev.104(1), 277-290). We view these simulations as a means to illustrating the fact that we economists are unaware of the value of key variables that determine the credibility of our own empirical findings. Such variables include priors (i.e., the pre-study probability that a tested phenomenon is true) and the statistical power of the empirical design. Economists should not hesitate to use Bayesian tools and meta-analysis in order to quantify what we know about these variables

One swallow doesn’t make a summer: reply to Kataria

In this paper we reply to Mitesh Kataria’s comment, which criticized the simulations of Maniadis, Tufano, and List (2014, Am. Econ. Rev.104(1), 277-290). We view these simulations as a means to illustrating the fact that we economists are unaware of the value of key variables that determine the credibility of our own empirical findings. Such variables include priors (i.e., the pre-study probability that a tested phenomenon is true) and the statistical power of the empirical design. Economists should not hesitate to use Bayesian tools and meta-analysis in order to quantify what we know about these variables