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Zeros of irreducible characters lying in a normal subgroupFeb 08 2019Let $N$ be a normal subgroup of a finite group $G$. An element $g\in G$ such that $\chi(g)=0$ for some irreducible character $\chi$ of $G$ is called a vanishing element of $G$. The aim of this paper is to analyse the influence of the $\pi$-elements in ... More

Prime power indices in factorised groupsMay 02 2017Let the group $G = AB$ be the product of the subgroups $A$ and $B$. We determine some structural properties of $G$ when the $p$-elements in $A\cup B$ have prime power indices in $G$, for some prime $p$. More generally, we also consider the case that all ... More

Products of groups and class sizes of $π$-elementsDec 21 2018We provide structural criteria for some finite factorised groups $G = AB$ when the conjugacy class sizes in $G$ of certain $\pi$-elements in $A\cup B$ are either $\pi$-numbers or $\pi'$-numbers, for a set of primes $\pi$. In particular, we extend for ... More

Square-free class sizes in products of groupsMar 24 2017We obtain some structural properties of a factorised group $G = AB$, given that the conjugacy class sizes of certain elements in $A\cup B$ are not divisible by $p^2$, for some prime $p$. The case when $G = AB$ is a mutually permutable product is especially ... More

On zeros of irreducible characters lying in a normal subgroupFeb 08 2019Feb 13 2019Let $N$ be a normal subgroup of a finite group $G$. An element $g\in G$ such that $\chi(g)=0$ for some irreducible character $\chi$ of $G$ is called a vanishing element of $G$. The aim of this paper is to analyse the influence of the $\pi$-elements in ... More

Zeros of irreducible characters in factorised groupsMar 01 2018An element $g$ of a finite group $G$ is said to be vanishing in $G$ if there exists an irreducible character $\chi$ of $G$ such that $\chi(g)=0$; in this case, $g$ is also called a zero of $G$. The aim of this paper is to obtain structural properties ... More

On zeros of irreducible characters lying in a normal subgroupFeb 08 2019Jul 28 2019Let $N$ be a normal subgroup of a finite group $G$. In this paper, we consider the elements $g$ of $N$ such that $\chi(g)\neq 0$ for all irreducible characters $\chi$ of $G$. Such an element is said to be non-vanishing in $G$. Let $p$ be a prime. If all ... More

Entanglement of boundary conditions giving rise to spontaneous symmetry breaking in quantum mechanicsFeb 15 2019We study spontaneous symmetry breaking in one dimensional quantum mechanical problems in terms of two-point boundary problems which lead to singular potentials containing Dirac delta functions and its derivatives. We search for broken-symmetry bound states. ... More

Periodic thin-film interference filters as one-dimensional photonic crystalsAug 11 2000Oct 10 2000We review photonic band gap related properties of a simple periodic system of thin dielectric layers. Properties associated with forbidden and allowed bands of such one-dimensional photonic crystals are presented. A revision of forbidden bands properties ... More

Unveiling causal activity of complex networksMar 17 2016Jul 29 2016We introduce a novel tool for analyzing complex network dynamics, allowing for cascades of causally-related events, which we call causal webs (c-webs), to be separated from other non-causally-related events. This tool shows that traditionally-conceived ... More

Fluctuations in fluids in thermal nonequilibrium states below the convective Rayleigh-Benard instabilitySep 13 2001Starting from the linearized fluctuating Boussinesq equations we derive an expression for the structure factor of fluids in stationary convection-free thermal nonequilibrium states, taking into account both gravity and finite-size effects. It is demonstrated ... More

Unveiling causal activity of complex networksMar 17 2016Aug 27 2017We introduce a novel tool for analyzing complex network dynamics, allowing for cascades of causally-related events, which we call causal webs (c-webs), to be separated from other non-causally-related events. This tool shows that traditionally-conceived ... More

Hydrodynamic Fluctuations in Laminar Fluid Flow. II. Fluctuating Squire EquationJun 19 2012We use fluctuating hydrodynamics to evaluate the enhancement of thermally excited fluctuations in laminar fluid flow using plane Couette flow as a representative example. In a previous publication [J. Stat. Phys. vol. 144 (2011) p. 774] we derived the ... More

A distance scale of planetary nebulae based on mid-infrared dataAug 11 2011Some of the most successful statistical methods for obtaining distances of planetary nebulae (PNe) are based on their apparent sizes and radio emission intensities. These methods have the advantage of being "extinction-free" and are especially suited ... More

Statistical mechanics of dissipative systemsApr 06 2002We propose a generalization of classical statistical mechanics which describes the behavior of dissipative systems placed in contact with a heat bath. In contrast to conventional statistical mechanics, which assigns probabilities to the states of the ... More

The central charge in three dimensional anti-de Sitter spaceJun 11 1998This paper collects the various ways of computing the central charge $c=3l/2G$ arising in 3d asymptotically anti-de Sitter spaces, in the Chern-Simons formulation. Their similarities and differences are displayed.

The Donation-Payment Gift Card Concept: how to give twice with one cardOct 09 2005Standard economic theory, starting with Adam Smith's invisible hand, holds that those who trade for their own selfish motives of maximizing their private preferences may contribute more to the public wealth than those who claim altruistic motives. Under ... More

Ellerman bombs and UV bursts: transient events in chromospheric current sheetsApr 25 2019Ellerman bombs (EBs) and UV bursts are both brightenings related to flux emergence regions and specifically to magnetic flux of opposite polarity that meet in the photosphere. These two reconnection-related phenomena, nominally formed far apart, occasionally ... More

Scalar field quantization on the 2+1 dimensional black hole backgroundOct 04 1993Nov 09 1993The quantization of a massless conformally coupled scalar field on the 2+1 dimensional Anti de Sitter black hole background is presented. The Green's function is calculated, using the fact that the black hole is Anti de Sitter space with points identified, ... More

An Analysis of the Quasicontinuum MethodMar 22 2001The aim of this paper is to present a streamlined and fully three-dimensional version of the quasicontinuum (QC) theory of Tadmor et al. and to analyze its accuracy and convergence characteristics. Specifically, we assess the effect of the summation rules ... More

Calculation of the specific heat in ultra-thin free-standing silicon membranesNov 12 2012The specific heat of ultra-thin free-standing membranes is calculated using the elastic continuum model. We first obtain the dispersion relations of the discrete set of acoustic modes in the system. The specific heat is then calculated by summing over ... More

Efficient fluorescence quenching in electrochemically exfoliated graphene decorated with gold nanoparticlesMay 23 2016High surface area graphene sheets were obtained by electrochemical exfoliation of graphite in an acid media under constant potential conditions. Filtration and centrifugation processes played an important role in order to obtain stable dispersions in ... More

On a List of Ordinary Differential Equations ProblemsAug 31 2018This evocative essay focuses on the mathematical activities witnessed by the author along 1962-64 at IMPA. The list of research problems proposed in September 1962 by Mauricio Peixoto at the Seminar on the Qualitative Theory of Differential Equations ... More

Physical origin of nonequilibrium fluctuation-induced forces in fluidsNov 12 2015Jan 13 2016Long-range thermal fluctuations appear in fluids in nonequilibrium states leading to fluctuation-induced Casimir-like forces. Two distinct mechanisms have been identified for the origin of the long-range nonequilibrium fluctuations in fluids subjected ... More

Shear-induced Casimir forces in liquid layersApr 17 2018Jan 24 2019In stationary nonequilibrium states a coupling between hydrodynamic modes causes thermal fluctuations to become long ranged inducing nonequilibrium Casimir forces or pressures. Here we consider nonequilibrium Casimir pressures induced in liquids by a ... More

Nonequilibrium fluctuation-induced Casimir pressures in liquid mixturesJan 14 2016In this article we derive expressions for Casimir-like pressures induced by nonequilibrium concentration fluctuations in liquid mixtures. The results are then applied to liquid mixtures in which the concentration gradient results from a temperature gradient ... More

Fluctuation-induced pressures in fluids in thermal nonequilibrium steady statesJan 07 2014Feb 17 2014Correlations in fluids in nonequilibrium steady states are long ranged. Hence, finite-size effects have important consequences in the nonequilibrium thermodynamics of fluids. One consequence is that nonequilibrium temperature fluctuations induce nonequilibrium ... More

Reliable Dispatch of Renewable Generation via Charging of Dynamic PEV PopulationsMay 24 2018The inherent storage of plug-in electric vehicles is likely to foster the integration of intermittent generation from renewable energy sources into existing power systems. In the present paper, we propose a three-stage scheme to the end of achieving dispatchability ... More

An Adaptive Finite Element Approach to Atomic-Scale Mechanics - The Quasicontinuum MethodOct 02 1997Mixed atomistic and continuum methods offer the possibility of carrying out simulations of material properties at both larger length scales and longer times than direct atomistic calculations. The quasi-continuum method links atomistic and continuum models ... More

Nonequilibrium Casimir pressures in liquids under shearJul 27 2019In stationary nonequilibrium states coupling between hydrodynamic modes causes thermal fluctuations to become long ranged inducing nonequilibrium Casimir pressures. Here we consider nonequilibrium Casimir pressures induced in liquids by a velocity gradient. ... More

Dynamics of fluctuations in a fluid below the onset of Rayleigh-Bénard convectionSep 30 2003We present experimental data and their theoretical interpretation for the decay rates of temperature fluctuations in a thin layer of a fluid heated from below and confined between parallel horizontal plates. The measurements were made with the mean temperature ... More

Non-equilibrium Casimir-like Forces in Liquid MixturesMar 12 2015Jun 19 2015In this Letter we consider a liquid mixture confined between two thermally conducting walls subjected to a stationary temperature gradient. While in a one-component liquid non-equilibrium fluctuation forces appear inside the liquid layer only, non-equilibrium ... More

Quasi-Critical Brain Dynamics on a Non-Equilibrium Widom LineMay 23 2014Dec 06 2014Is the brain really operating at a critical point? We study the non-equilibrium properties of a neural network which models the dynamics of the neocortex and argue for optimal quasi-critical dynamics on the Widom line where the correlation length is maximal. ... More

On the motion under focal attraction in a rotating mediumJan 29 2008New results are established here on the phase portraits and bifurcations of the kinematic model in a system of ODE's, first presented by H.K. Wilson in his 1971 book, and by him attributed to L. Markus (unpublished). A new, self-sufficient, study which ... More

Mathematical EncountersMar 24 2018Jul 29 2018This evocative essay focuses on mathematical activities witnessed by the author along 1962-64 at IMPA. The list of research problems proposed in September 1962 by Mauricio Peixoto at the Seminar on the Qualitative Theory of Differential Equations is pointed ... More

Quasicontinuum Models of Interfacial Structure and DeformationJul 09 1997Microscopic models of the interaction between grain boundaries (GBs) and both dislocations and cracks are of importance in understanding the role of microstructure in altering the mechanical properties of a material. A recently developed mixed atomistic ... More

Historical Comments on Monge's Ellipsoid and the Configuration of Lines of Curvature on Surfaces Immersed in ${\mathbb R}^3$Nov 18 2004This is an essay on the historical landmarks leading to the study of principal configurations on surfaces, their structural stability and further generalizations. Here it is pointed out that in the work of Monge, 1796, are found elements of the qualitative ... More

Non-equilibrium concentration fluctuations in binary liquids with realistic boundary conditionsMay 06 2015Sep 18 2015Because of the spatially long-ranged nature of spontaneous fluctuations in thermal non-equilibrium systems, they are affected by boundary conditions for the fluctuating hydrodynamic variables. In this paper we consider a liquid mixture between two rigid ... More

Giant Casimir effect in fluids in non-equilibrium steady statesFeb 19 2013Jun 12 2013In this letter we consider the fluctuation induced force exerted between two plates separated by a distance $L$ in a fluid with a temperature gradient. We predict that, for a range of distances $L$, this non-equilibrium force is anomalously large compared ... More

On the intensity contrast of solar photospheric faculae and network elementsJun 29 2002Sunspots, faculae and the magnetic network contribute to solar irradiance variations. The contribution due to faculae and the network is of basic importance, but suffers from considerable uncertainty. We determine the contrasts of active region faculae ... More

Definition of frame-invariant Soret coefficients for ternary mixturesOct 25 2018Jan 07 2019The definition of the Soret coefficient of a binary mixture includes a concentration prefactor, $x(1-x)$ when mol fraction $x$ is used, or $w(1-w)$ when mass fraction $w$ is used. In this paper the physical reasons behind this choice are reviewed, emphasizing ... More

Covariant path integrals and black holesOct 08 1997The thermal nature of the propagator in a collapsed black-hole spacetime is shown to follow from the non-trivial topology of the configuration space in tortoise coordinates by using the path integral formalism.

Thermal radiation in non-static curved spacetimes: quantum mechanical path integrals and configuration space topologyJul 21 1997Jun 19 1998A quantum mechanical path integral derivation is given of a thermal propagator in non-static Gui spacetime. The thermal nature of the propagator is understood in terms of homotopically non-trivial paths in the configuration space appropriate to tortoise ... More

Geological modeling using a recursive convolutional neural networks approachApr 27 2019Resource models are constrained by the extent of geological units that often depend on the lithology, alteration and mineralization. A three dimensional model of these geological units must be built from scarce information coming from drillholes and limited ... More

Coarse-Graining and Renormalization of Atomistic Binding Relations and Universal Macroscopic Cohesive BehaviorMay 24 2001We present two approaches for coarse-graining interplanar potentials and determining the corresponding macroscopic cohesive laws based on energy relaxation and the renormalization group. We analyze the cohesive behavior of a large---but finite---number ... More

An Exactly Solvable Phase-Field Theory of Dislocation Dynamics, Strain Hardening and Hysteresis in Ductile Single CrystalsSep 25 2001An exactly solvable phase-field theory of dislocation dynamics, strain hardening and hysteresis in ductile single crystals is developed. The theory accounts for: an arbitrary number and arrangement of dislocation lines over a slip plane; the long-range ... More

Magneto-transport in Disordered Graphene: from Weak Localization to Strong LocalizationMar 05 2010We present a magneto-transport study of graphene samples into which a mild disorder was introduced by exposure to ozone. Unlike the conductivity of pristine graphene, the conductivity of graphene samples exposed to ozone becomes very sensitive to temperature: ... More

Spectra of the Gurtin-Pipkin type equations with the kernel, depending on the parameterMar 18 2014In this paper, we study asymptotic behavior of the spectrum of the abstract Gurtin-Pipkin integro-differential equation with the kernel, depending on the parameter. The coefficients of this equation are unbounded and the main part is an abstract hyperbolic ... More

Correct solvability of hyperbolic Volterra equations with kernels depending on the parameterDec 02 2014We study the correct solvability of an abstract functional differential equations in Hilbert space, which includes integro-differential equations describing evolution of thermal phenomena, heat transfer in materials with memory or sound propagation in ... More

Chaos in the Y-chromosome evolution?Dec 01 2016The Y-chromosome degeneration is still an intriguing mechanism and comprises the very origin of sex. We present a coupled version of the well known logistic map and the logistic equation describing the evolution of XY chromosomes. Although chaos was found ... More

Probing M subdwarf metallicity with an esdK5+esdM5.5 binaryJul 28 2015We present a spectral analysis of the binary G 224-58 AB that consists of the coolest M extreme subdwarf (esdM5.5) and a brighter primary (esdK5). This binary may serve as a benchmark for metallicity measurement calibrations and as a test-bed for atmospheric ... More

Light Scattering from Nonequilibrium Concentration Fluctuations in a Polymer solutionFeb 24 2000We have performed light-scattering measurements in dilute and semidilute polymer solutions of polystyrene in toluene when subjected to stationary temperature gradients. Five solutions with concentrations below and one solution with a concentration above ... More

Thermal conductivity of disordered porous membranesOct 02 2018We report measurements and Monte Carlo simulations of thermal conductivity of porous 100nm- thick silicon membranes, in which size, shape and position of the pores were varied randomly. Measurements using 2-laser Raman thermometry on both plain membrane ... More

A Line-free Method of Monopoles for 3D Dislocation DynamicsJun 08 2018We develop an approximation scheme for three-dimensional dislocation dynamics in which the dislocation line density is concentrated at points, or monopoles. Every monopole carries a Burgers vector and an element of line. The monopoles move according to ... More

Probing the electron-phonon coupling in ozone-doped graphene by Raman spectroscopyMay 13 2010We have investigated the effects of ozone treatment on graphene by Raman scattering. Sequential ozone short-exposure cycles resulted in increasing the $p$ doping levels as inferred from the blue shift of the 2$D$ and $G$ peak frequencies, without introducing ... More

Superconducting properties of corner-shaped Al microstripsJan 11 2013Jan 17 2013The electrical transport properties of corner-shaped Al superconducting microstrips have been investigated. We demonstrate that the sharp turns lead to asymmetric vortex dynamics, allowing for easier penetration from the inner concave angle than from ... More

Anomalous flux avalanche morphology in a a-MoGe superconducting film with a square antidot lattice - experiment and simulationSep 12 2011We have employed magneto-optical imaging to visualize the occurrence of flux avalanches in a superconducting film of a-MoGe. The specimen was decorated with square antidots arranged in a square lattice. We observed avalanches with the anomalous habit ... More

A Constrained Sequential-Lamination Algorithm for the Simulation of Sub-Grid Microstructure in Martensitic MaterialsFeb 28 2002Oct 16 2002We present a practical algorithm for partially relaxing multiwell energy densities such as pertain to materials undergoing martensitic phase transitions. The algorithm is based on sequential lamination, but the evolution of the microstructure during a ... More

Boundary dynamics and the statistical mechanics of the 2+1 dimensional black holeFeb 11 1998Feb 04 1999We calculate the density of states of the 2+1 dimensional BTZ black hole in the micro- and grand-canonical ensembles. Our starting point is the relation between 2+1 dimensional quantum gravity and quantised Chern-Simons theory. In the micro-canonical ... More

Lovász theta type norms and Operator SystemsDec 22 2014To each graph on $n$ vertices there is an associated subspace of the $n \times n$ matrices called the operator system of the graph. We prove that two graphs are isomorphic if and only if their corresponding operator systems are unitally completely order ... More

Study of Pairing Correlations in the Attractive Hubbard Model on Chains, Ladders, and SquaresDec 07 1999We report the results of zero temperature quantum Monte Carlo simulations and zero temperature mean-field calculations of the attractive Hubbard model on chains, ladders, and square lattices. We investigated the predictability of the BCS approximation, ... More

Navigability of temporal networks in hyperbolic spaceSep 08 2017Information routing is one of the main tasks in many complex networks with a communication function. Maps produced by embedding the networks in hyperbolic space can assist this task enabling the implementation of efficient navigation strategies. However, ... More

A bilayer Double Semion Model with Symmetry-Enriched Topological OrderApr 29 2016Sep 14 2016We construct a new model of two-dimensional quantum spin systems that combines intrinsic topo- logical orders and a global symmetry called flavour symmetry. It is referred as the bilayer Doubled Semion model (bDS) and is an instance of symmetry-enriched ... More

Confinement Effects in AntiferromagnetsApr 11 2000Phase equilibrium in confined Ising antiferromagnets was studied as a function of the coupling (v) and a magnetic field (h) at the surfaces, in the presence of an external field H. The ground state properties were calculated exactly for symmetric boundary ... More

Zero Temperature Phases of the Electron GasOct 09 1998The stability of different phases of the three-dimensional non-relativistic electron gas is analyzed using stochastic methods. With decreasing density, we observe a {\it continuous} transition from the paramagnetic to the ferromagnetic fluid, with an ... More

On the Characterization of $τ_{(n)}$-AtomsMay 07 2019In 2011, Anderson and Frazier define the concept of $\tau_{(n)}$-factorization, where $\tau_{(n)}$ is a restriction of the modulo $n$ equivalence relation. These relations have been worked mostly for small values of $n$. However, it is sometimes difficult ... More

A general approach to the assessment of uncertainty in volumes by using the multi-Gaussian modelJul 18 2019The goal of this research is to derive an approach to assess uncertainty in an arbitrary volume conditioned by sampling data, without using geostatistical simulation. We have accomplished this goal by deriving an numerical tool suitable for any probabilistic ... More

Correlated Wave-Functions and the Absence of Long Range Order in Numerical Studies of the Hubbard ModelSep 02 1998We present a formulation of the Constrained Path Monte Carlo (CPMC) method for fermions that uses trial wave-functions that include many-body effects. This new formulation allows us to implement a whole family of generalized mean-field states as constraints. ... More

Re-evaluation of Neutron-4He Elastic Scattering Data near 20 MeVApr 10 2011Oct 02 2012Measured differential elastic scattering cross sections of 17.71-, 20.97-, and 23.72-MeV neutrons from liquid helium-4 were re-evaluated and corrected for sample size and multiple scattering effects by means of a Monte Carlo technique implemented in a ... More

A Micromechanical Model of Hardening, Rate Sensitivity and Thermal Softening in BCC Single CrystalsMar 13 2001The present paper is concerned with the development of a micromechanical model of the hardening, rate-sensitivity and thermal softening of bcc crystals. In formulating the model we specifically consider the following unit processes: double-kink formation ... More

Quantum mechanical composition laws in reparameterization invariant systemsAug 20 1993This paper gives a brief description of the derivation of a composition law for the propagator of a relativistic particle, in a sum over histories quantization. The extension of this derivation to the problem of finding a composition law for quantum cosmology ... More

Enhancement of pinning properties of superconducting thin films by graded pinning landscapesJan 26 2013A graded distribution of pinning centers (antidots) in superconducting MoGe thin films has been investigated by magnetization and magneto-optical imaging. The pinning landscape has maximum density at the border, decreasing progressively towards the center. ... More

Supersymmetry breaking, conserved charges and stability in N=1 Super KdVNov 08 2012We analyse the non-abelian algebra and the supersymmetric cohomology associated to the local and non-local conserved charges of N=1 SKdV under Poisson brackets. We then consider the breaking of the supersymmetry and obtain an integrable model in terms ... More

A metric property of umbilic pointsMay 13 2003In the space $\mathbb U^4$ of cubic forms of surfaces, regarded as a $G$-space and endowed with a natural invariant metric, the ratio of the volumes of those representing umbilic points with negative to those with positive indexes is evaluated in terms ... More

Geometric Mean Curvature Lines on Surfaces Immersed in R3Feb 17 2003Here are studied pairs of transversal foliations with singularities, defined on the Elliptic region (where the Gaussian curvature $\mathcal K$ is positive) of an oriented surface immersed in $\mathbb R^3$. The leaves of the foliations are the lines of ... More

Lines of Curvature on Quadric Hypersurfaces of $ \mathbb{R}^4$Sep 28 2015Here are described the geometric structures of the lines of principal curvature and the partially umbilic singularities of the tridimensional non compact generic quadric hypersurfaces of ${\mathbb R}^4$. This includes the ellipsoidal hyperboloids of one ... More

Tori Embedded in S3 with Dense Asymptotic LinesOct 11 2008In this paper are given examples of tori T^2 embedded in S^3 with all their asymptotic lines dense.

Lines of Curvature on Surfaces, Historical Comments and Recent DevelopmentsDec 10 2007This survey starts with the historical landmarks leading to the study of principal configurations on surfaces, their structural stability and further generalizations. Here it is pointed out that in the work of Monge, 1796, are found elements of the qualitative ... More

Poisson structure and stability analysis of a coupled system arising from the supersymmetric breaking of Super KdVJul 29 2014The Poisson structure of a coupled system arising from a supersymmetric breaking of N=1 Super KdV equations is obtained. The supersymmetric breaking is implemented by introducing a Clifford algebra instead of a Grassmann algebra. The Poisson structure ... More

Lines of Mean Curvature on Surfaces Immersed in R3Mar 29 2004Associated to oriented surfaces immersed in R^3 here are studied pairs of transversal foliations with singularities, defined on the Elliptic region, where the Gaussian curvature K, given by the product of the principal curvatures k_1, k_2 of the immersion, ... More

Quantum Graph Homomorphisms via Operator SystemsMay 03 2015Feb 20 2016We explore the concept of a graph homomorphism through the lens of C$^*$-algebras and operator systems. We start by studying the various notions of a quantum graph homomorphism and examine how they are related to each other. We then define and study a ... More

Tunneling measurement of quantum spin oscillationsDec 03 2002Jul 01 2003We consider the problem of tunneling between two leads via a localized spin 1/2 or any other microscopic system which can be modeled by a two-level Hamiltonian. We assume that a constant magnetic field ${\bf B}_0$ acts on the spin, that electrons in the ... More

On Modular Invariance and 3D Gravitational InstantonsMar 25 1999Jun 30 1999We study the modular transformation properties of Euclidean solutions of 3D gravity whose asymptotic geometry has the topology of a torus. These solutions represent saddle points of the grand canonical partition function with an important example being ... More

Stability of solitonic solutions of Super KdV equations under Susy breaking conditionsJul 25 2012Jul 01 2013A supersymmetric breaking procedure for N=1 Super KdV, preserving the positivity of the hamiltonian as well as the existence of solitonic solutions, is implemented. The resulting integrable system is shown to have nice stability properties.

Tori Embedded in R3 with Dense Principal LinesNov 02 2008In this paper are given examples of tori T2 embedded in R3 with all their principal lines dense. These examples are obtained by stereographic projection of deformations of the Clifford torus in S3.

Data mining and accelerated electronic structure theory as a tool in the search for new functional materialsAug 15 2008Data mining is a recognized predictive tool in a variety of areas ranging from bioinformatics and drug design to crystal structure prediction. In the present study, an electronic structure implementation has been combined with structural data from the ... More

Exchange-Correlation Hole in Polarized Insulators: Implications for the Microscopic Functional Theory of DielectricsSep 05 1997We present a simple and direct proof that the exchange-correlation hole, and therefore the exchange-correlation energy, in a polarized insulator is not determined by the bulk density alone. It is uniquely characterized by the density and the macroscopic ... More

Geometric randomization of real networks with prescribed degree sequenceDec 16 2018We introduce a model for the randomization of complex networks with geometric structure. The geometric randomization (GR) model assumes a homogeneous distribution of the nodes in an underlying similarity space and uses rewirings of the links to find configurations ... More

Braneworld Gravity under gravitational decouplingJul 26 2019The main objective of this work is to study in some detail the Randall-Sundrum gravity under the gravitational decoupling through the minimal geometric deformation approach (MGD-decoupling). We show a family of new black hole solutions as well as new ... More

Magnetic and electronic properties at the gamma-Al2O3/SrTiO3 interfaceJan 28 2019The magnetic and electronic nature of the gamma-Al2O3/SrTiO3 spinel/perovskite interface is explored by means of x-ray absorption spectroscopy. Polarized x-ray techniques combined with atomic multiplet calculations reveal localized magnetic moments assigned ... More

A novel high resolution contactless technique for thermal field mapping and thermal conductivity determination: Two-Laser Raman ThermometryDec 30 2013We present a novel high resolution contactless technique for thermal conductivity determination and thermal field mapping based on creating a thermal distribution of phonons using a heating laser, while a second laser probes the local temperature through ... More

Stable piecewise polynomial vector fieldsJan 04 2012Sep 19 2012Consider in R^2 the semi-planes N={y>0} and S={y<0}$ having as common boundary the straight line D={y=0}$. In N and S are defined polynomial vector fields X and Y, respectively, leading to a discontinuous piecewise polynomial vector field Z=(X,Y). This ... More

Bifurcations in a class of polycycles involving two saddle-nodes on a Mobius bandOct 10 2008In this paper we study the bifurcations of a class of polycycles, called lips, occurring in generic three-parameter smooth families of vector fields on a M\"obius band. The lips consists of a set of polycycles formed by two saddle-nodes, one attracting ... More

Full hamiltonian structure for a parametric coupled Korteweg-de Vries systemSep 08 2014We obtain the full hamiltonian structure for a parametric coupled KdV system. The coupled system arises from four different real basic lagrangians. The associated hamiltonian functionals and the corresponding Poisson structures follow from the geometry ... More

Hamiltonian structure of an operator valued extension of Super KdV equationsJul 29 2014An extension of the super Korteweg-de Vries integrable system in terms of operator valued functions is obtained. In particular the extension contains the $N=1$ Super KdV and coupled systems with functions valued on a symplectic space. We introduce a Miura ... More

The Hamiltonian structure of a coupled system derived from a supersymmetric breaking of Super KdV equationsJun 03 2013A supersymmetric breaking procedure for $N=1$ Super KdV, using a Clifford algebra, is implemented. Dirac's method for the determination of constraints is used to obtain the Hamiltonian structure, via a Lagrangian, for the resulting solitonic system of ... More

A simple method to generate exact physically acceptable anisotropic solutions in general relativityNov 03 2018By using the gravitational decoupling through the minimal geometric deformation approach (MGD-decoupling), we show a simple and powerful method to generate physically acceptable exact analytical solutions for anisotropic stellar distributions in general ... More

Codimension two Umbilic points on Surfaces Immersed in R^3Jan 11 2006In this paper is studied the behavior of lines of curvature near umbilic points that appear generically on surfaces depending on two parameters.

On the Patterns of Principal Curvature Lines around a Curve of Umbilic PointsNov 01 2004In this paper is studied the behavior of principal curvature lines near a curve of umbilic points of a smooth surface.

Harmonic Mean Curvature Lines on Surfaces Immersed in R3Feb 18 2003Consider oriented surfaces immersed in $\mathbb R^3.$ Associated to them, here are studied pairs of transversal foliations with singularities, defined on the Elliptic region, where the Gaussian curvature $\mathcal K$, given by the product of the principal ... More