Results for "Fernando A. Oliveira"

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On the existence of an upper critical dimension for systems within the KPZ universality classFeb 21 2015In this work we extend the etching model to $d+1$ dimensions. This permits us to investigate its exponents behaviour on higher dimensions, to try to verify the existence of an upper critical dimension for the KPZ equations, with our results sugesting ... More
Critical behavior of noise-induced phase synchronizationJun 26 2016In this article, we present a systematic study of the critical behavior of phase oscillators with multiplicative noise from a thermodynamic equilibrium approach. We have already presented the thermodynamics of phase noise oscillators and mapped out in ... More
Normal Stress Distribution of Rough Surfaces in ContactMay 01 2000We study numerically the stress distribution on the interface between two thick elastic media bounded by interfaces that include spatially correlated asperities. The interface roughness is described using the self-affine topography that is observed over ... More
C2 densely the 2-sphere has an elliptic closed geodesicNov 29 2003We prove that a riemannian metric on the 2-sphere or the projective plane can be C2-approximated by a smooth metric whose geodesic flow has an elliptic closed geodesic.
On the Transitivity of Invariant Manifolds of Conservative FlowsFeb 28 2015Mar 05 2015The main result of this work is the fact that for volume preserving flows, $C^r$-generically, the closure of an invariant manifold is a chain transitive set. We also develop a flow box and local perturbation techniques which excel by their simplicity. ... More
Spatio-temporal conjecture for diffusionFeb 01 2005We present here a conjecture about the equivalence between the noise density of states of a system governed by a generalized Langevin equation and the fluctuation in the energy density of states in a Hamiltonian system. We present evidence of this for ... More
Complexity perspectives: an anomalous diffusion approachAug 13 2009Aug 14 2009The science of complexity is far from being fully understood and even its foundations are not well established. On the other hand, during the last decade, the random motion of particles or waves - the so-called diffusion - has been known better. In this ... More
On the Transitivity of Invariant Manifolds of Conservative FlowsFeb 28 2015Dec 08 2016The main result of this work is the following: for volume preserving flows on compact manifolds with the $C^r$ topology, $1 \leqq r \leqq \infty$ , the closure of every invariant manifold of periodic orbits and singularities is a chain transitive set. ... More
Thermodynamic and dynamic anomalies in a one dimensional lattice model of liquid waterSep 23 2010We investigate the occurrence of waterlike thermodynamic and dynamic anomalous behavior in a one dimensional lattice gas model. The system thermodynamics is obtained using the transfer matrix technique and anomalies on density and thermodynamic response ... More
Residual entropy and waterlike anomalies in the repulsive one dimensional lattice gasMar 10 2015The thermodynamic and kinetics of the one dimensional lattice gas with repulsive interaction is investigated using transfer matrix technique and Monte Carlo simulations. This simple model is shown to exhibit waterlike anomalies in density, thermal expansion ... More
Mixing, ergodicity and slow relaxation phenomenaOct 10 2006Oct 20 2006Investigations on diffusion in systems with memory [I.V.L. Costa, R. Morgado, M.V.B.T. Lima, F.A. Oliveira, Europhys. Lett. 63 (2003) 173] have established a hierarchical connection between mixing, ergodicity, and the fluctuation-dissipation theorem (FDT). ... More
Nonergodic Brownian Dynamics and the Fluctuation-Dissipation TheoremMay 03 2006Nonergodic Brownian motion is elucidated within the framework of the generalized Langevin equation. For thermal noise yielding either a vanishing or a divergent zero-frequency friction strength, the non-Markovian Browninan dynamics exhibits a riveting, ... More
Khinchin theorem and anomalous diffusionOct 31 2008Dec 10 2008A recent paper [M. H. Lee, Phys. Rev. Lett. 98, 190601 (2007)] has called attention to the fact that irreversibility is a broader concept than ergodicity, and that therefore the Khinchin theorem [A. I. Khinchin, Mathematical Foundations of Statistical ... More
Anomalous law of coolingDec 15 2014Mar 04 2015We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergo a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton's ... More
Violation of the fluctuation-dissipation theorem for fast superdiffusionApr 11 2003We study anomalous diffusion for one-dimensional systems described by a generalized Langevin equation. We show that superdiffusion can be classified in normal superdiffusion and fast superdiffusion. For fast superdiffusion, we prove that the Fluctuation-Dissipation ... More
Anomalous diffusion: A basic mechanism for the evolution of inhomogeneous systemsFeb 08 2019In this article we review classical and recent results in anomalous diffusion and provide mechanisms useful for the study of the fundamentals of certain processes, mainly in condensed matter physics, chemistry and biology. Emphasis will be given to some ... More
Computing upper bounds for the packing density of congruent copies of a convex bodyAug 22 2013Jul 06 2016In this paper we prove a theorem that provides an upper bound for the density of packings of congruent copies of a given convex body in $\mathbb{R}^n$; this theorem is a generalization of the linear programming bound for sphere packings. We illustrate ... More
Fourier analysis, linear programming, and densities of distance avoiding sets in R^nAug 13 2008Dec 02 2008In this paper we derive new upper bounds for the densities of measurable sets in R^n which avoid a finite set of prescribed distances. The new bounds come from the solution of a linear programming problem. We apply this method to obtain new upper bounds ... More
Pattern transitions in a nonlocal logistic map for populationsJan 26 2016Sep 14 2016In this work, we study the pattern solutions of doubly nonlocal logistic map that include spatial kernels in both growth and competition terms. We show that this map includes as a particular case the nonlocal Fisher-Kolmogorov equation, and we demonstrate ... More
A quantitative version of Steinhaus' theorem for compact, connected, rank-one symmetric spacesMay 04 2010Jan 10 2013Let $d_1$, $d_2$, ... be a sequence of positive numbers that converges to zero. A generalization of Steinhaus' theorem due to Weil implies that, if a subset of a homogeneous Riemannian manifold has no pair of points at distances $d_1$, $d_2$, ... from ... More
Mathematical optimization for packing problemsMar 05 2014Nov 15 2015During the last few years several new results on packing problems were obtained using a blend of tools from semidefinite optimization, polynomial optimization, and harmonic analysis. We survey some of these results and the techniques involved, concentrating ... More
Tight Bounds for the Entanglement of Formation of Gaussian StatesOct 22 2013Jan 31 2014We establish tight upper and lower bounds for the Entanglement of Formation of an arbitrary two-mode Gaussian state employing necessary properties of Gaussian channels. Both bounds are strictly given by the Entanglement of Formation of symmetric Gaussian ... More
Upper bounds for packings of spheres of several radiiJun 12 2012We give theorems that can be used to upper bound the densities of packings of different spherical caps in the unit sphere and of translates of different convex bodies in Euclidean space. These theorems extend the linear programming bounds for packings ... More
The zero-inflated promotion cure rate regression model applied to fraud propensity in bank loan applicationsOct 01 2015In this paper we extend the promotion cure rate model proposed by Chen et al (1999), by incorporating excess of zeros in the modelling. Despite allowing to relate the covariates to the fraction of cure, the current approach, which is based on a biological ... More
The zero-inflated cure rate regression model: Applications to fraud detection in bank loan portfoliosSep 17 2015Sep 19 2015In this paper, we introduce a methodology based on the zero-inflated cure rate model to detect fraudsters in bank loan applications. In fact, our approach enables us to accommodate three different types of loan applicants, i.e., fraudsters, those who ... More
Improving the semidefinite programming bound for the kissing number by exploiting polynomial symmetrySep 16 2016The kissing number of $\mathbb{R}^n$ is the maximum number of pairwise-nonoverlapping unit spheres that can simultaneously touch a central unit sphere. Mittelmann and Vallentin (2010), based on the semidefinite programming bound of Bachoc and Vallentin ... More
Grothendieck inequalities for semidefinite programs with rank constraintNov 08 2010May 04 2012Grothendieck inequalities are fundamental inequalities which are frequently used in many areas of mathematics and computer science. They can be interpreted as upper bounds for the integrality gap between two optimization problems: a difficult semidefinite ... More
A variational problem associated to a hyperbolic Caffarelli--Kohn--Nirenberg inequalityNov 16 2017We prove a Caffarelli--Kohn--Nirenberg inequality in the hyperbolic space. For a semilinear elliptic equation involving the associated weighted Laplace--Beltrami operator, we establish variationally the existence of positive radial solutions in the subcritical ... More
Accuracy of generalized gradient approximation functionals for density functional perturbation theory calculationsSep 18 2013We assess the validity of various exchange-correlation functionals for computing the structural, vibrational, dielectric, and thermodynamical properties of materials in the framework of density-functional perturbation theory (DFPT). We consider five generalized-gradient ... More
Modified Theories of Gravity: Traversable WormholesJul 13 2011This MSc thesis is divided in to two parts. The first, covers the foundations of theories of gravitation, and, the second incorporates original work on the subject of the existence of traversable wormholes in $f(R)$ modified theories of gravity. A short ... More
Superconducting instability of a non-magnetic metallic band in an antiferromagnetic backgroundAug 30 2013It is shown that a non-magnetic metallic band in the presence of an antiferromagnetic background coupled only by the exchange interaction develops a superconducting instability similar to the one described by BCS theory plus additional terms that strongly ... More
A Conforming Primal-Dual Mixed Formulation for the 2D Multiscale Porous Media Flow ProblemJan 04 2017Oct 02 2018In this paper a new primal-dual mixed finite element method is introduced, aimed to model multiscale problems with several geometric subregions in the domain of interest. In each of these regions porous media fluid flow takes place, but governed by physical ... More
Notes on the nonlinear dependence of a multiscale coupled system with respect to the interfaceDec 25 2013Mar 15 2014This work studies the dependence of the solution with respect to interface geometric perturbations in a multiscaled coupled Darcy flow system in direct variational formulation. A set of admissible perturbation functions and a sense of convergence are ... More
Systematic reduction of sign errors in many-body problems: generalization of self-healing diffusion Monte Carlo to excited statesJun 24 2009Aug 16 2009A recently developed self-healing diffusion Monte Carlo algorithm [PRB 79, 195117] is extended to the calculation of excited states. The formalism is based on an excited-state fixed-node approximation and the mixed estimator of the excited-state probability ... More
On the Construction of Geometric Parameters for Preferential Fluid Flow Information in Fissured MediaFeb 19 2014For a fissured medium, we analyze the impact that the geometry of the cracks, has in the phenomenon of preferential fluid flow. Using finite volume meshes we analyze the mechanical energy dissipation due to gravity, curvature of the surface and friction ... More
On the Homogenization of Geological Fissured Systems With Curved non-periodic CracksDec 14 2013We analyze the steady fluid flow in a porous medium containing a network of thin fissures i.e. width $\mathcal{O}(\epsilon)$, where all the cracks are generated by the rigid translation of a continuous piecewise $C^{1}$ functions in a fixed direction. ... More
On pointed Hopf algebras associated to unmixed conjugacy classes in S_nAug 28 2006Let s in S_n be a product of disjoint cycles of the same length, C the conjugacy class of s and rho an irreducible representation of the isotropy group of s. We prove that either the Nichols algebra B(C, rho) is infinite-dimensional, or the braiding of ... More
There is no anomaly in the nonlocality of two entangled qutritsApr 07 2015Sep 04 2015There is no doubt about the fact that entanglement and nonlocality are distinct resources. It is acknowledged that a clear illustration of this point is the difference between maximally entangled states and states that maximally violate a Bell inequality. ... More
Robust Output Regulation of Linear Passive Systems with Multivalued Upper Semicontinuous ControlsDec 05 2014The use of multivalued controls derived from a special maximal monotone operator are studied in this note. Starting with a strictly passive linear system (with possible parametric uncertainty and external disturbances) a multivalued control law is derived, ... More
Canonical formulation of Poincare BFCG theory and its quantizationSep 12 2014Mar 29 2015We find the canonical formulation of the Poincare BFCG theory in terms of the spatial 2-connection and its canonically conjugate momenta. We show that the Poincare BFCG action is dynamically equivalent to the BF action for the Poincare group and we find ... More
New criteria for cluster identification in continuum systemsOct 24 2001Oct 25 2001Two new criteria, that involve the microscopic dynamics of the system, are proposed for the identification of clusters in continuum systems. The first one considers a residence time in the definition of the bond between pairs of particles, whereas the ... More
Localized orientational order chaperons the nucleation of Rotator phases in hard polyhedral particlesNov 11 2013The nucleation kinetics of the rotator phase in hard cuboctahedra, truncated octahedra, and rhombic dodecahedra is simulated via a combination of Forward Flux Sampling and Umbrella Sampling. For comparable degree of supersaturation, the polyhedra are ... More
Generalizing the self-healing diffusion Monte Carlo approach to finite temperature: a path for the optimization of low-energy many-body basesSep 18 2013A statistical method is derived for the calculation of thermodynamic properties of many-body systems at low temperatures. This method is based on the self-healing diffusion Monte Carlo method for complex functions [F. A. Reboredo J. Chem. Phys. 136, 204101 ... More
New assessment on the nonlocality of correlation boxesMay 15 2016Correlation boxes are hypothetical systems capable of producing the maximal algebraic violation of Bell inequalities, beyond the quantum bound and without superluminal signaling. The fact that these systems show stronger correlations than those presented ... More
Bell states and entanglement dynamics on two coupled quantum moleculesMar 03 2015Mar 06 2015This work provides a complete description of entanglement properties between electrons inside coupled quantum molecules, nanoestructures which consist of two quantum dots. Each electron can tunnel between the two quantum dots inside the molecule, being ... More
A New Version of Dirac's AEther and Its Cosmological ApplicationsDec 27 2002We propose a new formulation for the AEther of Dirac based on a lagrangian approach. We analyse how the presence of a particular self-interaction term in the lagrangian lead us to a description of the aether as being a medium with conductivity which is ... More
Spin-Orbit Coupling in Diamond and Zincblende HeterostructuresJul 12 2004Spin splittings in III-V materials and heterostructures are of interest because of potential applications, mainly in spintronic devices. A necessary condition for the existence of these spin splittings is the absence of inversion symmetry. In bulk zincblende ... More
Evolution of Collective Behaviors for a Real Swarm of Aquatic Surface RobotsNov 10 2015Feb 02 2016Swarm robotics is a promising approach for the coordination of large numbers of robots. While previous studies have shown that evolutionary robotics techniques can be applied to obtain robust and efficient self-organized behaviors for robot swarms, most ... More
Lower bounds for measurable chromatic numbersJan 07 2008Jul 17 2009The Lovasz theta function provides a lower bound for the chromatic number of finite graphs based on the solution of a semidefinite program. In this paper we generalize it so that it gives a lower bound for the measurable chromatic number of distance graphs ... More
Better bounds for planar sets avoiding unit distancesDec 31 2014Oct 26 2015A $1$-avoiding set is a subset of $\mathbb{R}^n$ that does not contain pairs of points at distance $1$. Let $m_1(\mathbb{R}^n)$ denote the maximum fraction of $\mathbb{R}^n$ that can be covered by a measurable $1$-avoiding set. We prove two results. First, ... More
Flag Algebras: A First GlanceJul 16 2016The theory of flag algebras, introduced by Razborov in 2007, has opened the way to a systematic approach to the development of computer-assisted proofs in extremal combinatorics. It makes it possible to derive bounds for parameters in extremal combinatorics ... More
Experimental investigation of the softening-stiffening response of tensegrity prisms under compressive loadingJun 04 2014Jun 21 2014The present paper is concerned with the formulation of new assembly methods of bi-material tensegrity prisms, and the experimental characterization of the compressive response of such structures. The presented assembly techniques are easy to implement, ... More
Mass and Extremals Associated with the Hardy-Schrödinger Operator on Hyperbolic SpaceOct 03 2017Apr 05 2018We consider the Hardy-Schr\"odinger operator $ -\Delta_{\mathbb{B}^n}-\gamma{V_2}$ on the Poincar\'e ball model of the Hyperbolic space ${\mathbb{B}^n}$ ($n \geq 3$). Here $V_2$ is a well chosen radially symmetric potential, which behaves like the Hardy ... More
Surface and bulk properties of ballistic deposition models with bond breakingAug 08 2012Feb 17 2013We introduce a new class of growth models, with a surface restructuring mechanism in which impinging particles may dislodge suspended particles, previously aggregated on the same column in the deposit. The flux of these particles is controlled through ... More
On the generation of bipartite grids with controlled regularity for 2-D and 3-D simply connected domainsDec 25 2013We present a procedure to generate bipartite grids for simply connected domains in 2-D and 3-D of prescribed size and controlled regularity elements. The mesh elements $K$ of the triangulation satisfy $\zeta_{K} \leq C$ where $\zeta_{K}$ is the regularity ... More
On the Implementation and Assessment of several Divide & Conquer Matheuristic Strategies for the solution of the Knapsack ProblemJan 04 2019We introduce and asses a Divide \& Conquer heuristic method, aimed to solve large instances of the Knapsack Problem. The method subdivides a large problem in two smaller ones (or recursive iterations of the same principle), to lower down the global computational ... More
Open string with a background B-field as the first order mechanics and noncommutativityOct 19 2001To study noncommutativity properties of the open string with constant B-field we construct a mechanical action which reproduces classical dynamics of the string sector under consideration. It allows one to apply the Dirac quantization procedure for constrained ... More
Using the Galileoscope in astronomical observationsJan 28 2015This project aims to attract school students and teachers from the state education system from Ca\c{c}apava do Sul - RS to Sciences and specially to Astronomy. We made astronomical observations using a Galileoscope choosing the Moon as a primary target. ... More
On the Suitability of PLC Pulses for Power Line Fault Sensing via Time-Domain ReflectometryJan 23 2019This work discusses the suitability of typical power line communication (PLC) pulses for fault sensing in power lines via pulse-compression time-domain reflectometry (TDR). For this purpose, we first carefully outline a TDR system operating over a power ... More
A highly optimized flow-correlation attackOct 17 2013Deciding that two network flows are essentially the same is an important problem in intrusion detection and in tracing anonymous connections. A stepping stone or an anonymity network may try to prevent flow correlation by adding chaff traffic, splitting ... More
Predictions Based on the Clustering of Heterogeneous Functions via Shape and Subject-Specific CovariatesMay 11 2015We consider a study of players employed by teams who are members of the National Basketball Association where units of observation are functional curves that are realizations of production measurements taken through the course of one's career. The observed ... More
Directly accessible entangling gates for capacitively coupled singlet-triplet qubitsSep 22 2014Jan 09 2015The recent experimental advances in capacitively coupled singlet-triplet qubits, particularly the demonstration of entanglement, opens the question of what type of entangling gates the system's Hamiltonian can produce directly via a single square pulse. ... More
Linking Correlated Network Flows through Packet Timing: a Game-Theoretic ApproachJul 11 2013Deciding that two network flows are essentially the same is an important problem in intrusion detection or in tracing anonymous connections. A stepping stone or an anonymity network may try to prevent flow correlation by delaying the packets, introducing ... More
Fluid flow on 3D triangulated fissures: conservative piece-wise constant velocity fields and associated transport processesNov 28 2016For a fissured medium with uncertainty in the knowledge of fractures' geometry, a conservative tangential flow field is constructed, which is consistent with the physics of stationary fluid flow in porous media and an interpolated geometry of the cracks. ... More
Estimation of genetic diversity in viral populations from next generation sequencing data with extremely deep coverageMay 08 2014Apr 24 2015In this paper we propose a method and discuss its computational implementation as an integrated tool for the analysis of viral genetic diversity on data generated by high-throughput sequencing. Most methods for viral diversity estimation proposed so far ... More
A semiclassical trace formula for the canonical partition function of one dimensional systemsJul 20 2006Sep 05 2006We present a semiclassical trace formula for the canonical partition function of arbitrary one-dimensional systems. The approximation is obtained via the stationary exponent method applied to the phase-space integration of the density operator in the ... More
Biot-Savart-like law in electrostaticsNov 07 2000The Biot-Savart law is a well-known and powerful theoretical tool used to calculate magnetic fields due to currents in magnetostatics. We extend the range of applicability and the formal structure of the Biot-Savart law to electrostatics by deriving a ... More
Susceptibility of a two-level atom near an isotropic photonic band edge: transparency and band edge profile reconstructionMar 14 2015We discuss the necessary conditions for a two-level system in the presence of an isotropic band edge to be transparent to a probe laser field. The two-level atom is transparent whenever it is coupled to a reservoir constituted of two parts - a flat and ... More
Wormhole geometries in f(R) modified theories of gravitySep 30 2009Oct 20 2009In this work, we construct traversable wormhole geometries in the context of f(R) modified theories of gravity. We impose that the matter threading the wormhole satisfies the energy conditions, so that it is the effective stress-energy tensor containing ... More
Dynamical Lower Bounds for 1D Dirac OperatorsAug 07 2007Quantum dynamical lower bounds for continuous and discrete one-dimensional Dirac operators are established in terms of transfer matrices. Then such results are applied to various models, including the Bernoulli-Dirac one and, in contrast to the discrete ... More
Dissipative Stern-Gerlach recombination experimentJan 11 2006The possibility of obtaining the initial pure state in a usual Stern-Gerlach experiment through the recombination of the two emerging beams is investigated. We have extended the previous work of Englert, Schwinger and Scully \cite{ISG1} including the ... More
Reliability of digitized quantum annealing and the decay of entanglementNov 01 2016Nov 10 2016We performed a banged-digital-analog simulation of a quantum annealing protocol in a two-qubit Nuclear Magnetic Resonance (NMR) quantum computer. Our experimental simulation employed up to 235 Trotter steps, with more than 2000 gates (pulses), and we ... More
Power law Kohn anomalies and the excitonic transition in grapheneFeb 25 2012Dirac electrons in graphene in the presence of Coulomb interactions of strength $\beta$ have been shown to display power law behavior with $\beta$ dependent exponents in certain correlation functions, which we call the mass susceptibilities of the system. ... More
Case-Factor Diagrams for Structured Probabilistic ModelingJul 11 2012We introduce a probabilistic formalism subsuming Markov random fields of bounded tree width and probabilistic context free grammars. Our models are based on a representation of Boolean formulas that we call case-factor diagrams (CFDs). CFDs are similar ... More
Partially hyperbolic geodesic flowsOct 05 2011Mar 11 2013We construct a category of examples of partially hyperbolic geodesic flows which are not Anosov, deforming the metric of a compact locally symmetric space of nonconstant negative curvature. Candidates for such example as the product metric and locally ... More
Optimization Problems in Correlated NetworksFeb 24 2015Jan 31 2016Solving the shortest path and the min-cut problems are key in achieving high performance and robust communication networks. Those problems have often beeny studied in deterministic and independent networks both in their original formulations as well as ... More
Index statistical properties of sparse random graphsSep 04 2015Using the replica method, we develop an analytical approach to compute the characteristic function for the probability $\mathcal{P}_N(K,\lambda)$ that a large $N \times N$ adjacency matrix of sparse random graphs has $K$ eigenvalues below a threshold ... More
Mather problem and viscosity solutions in the stationary settingMar 09 2009In this paper we discuss the Mather problem for stationary Lagrangians, that is Lagrangians $L:\Rr^n\times \Rr^n\times \Omega\to \Rr$, where $\Omega$ is a compact metric space on which $\Rr^n$ acts through an action which leaves $L$ invariant. This setting ... More
Mass Terms in Two-Higgs Doublet ModelsDec 14 2001Feb 11 2003We take a closer look at the mass terms of all renormalizable and CP conserving two-Higgs doublet models (THDM). We show how some of the dimension two parameters in the potential can be set equal to zero leading to relations among the tree-level parameters ... More
Retinal vessel segmentation based on Fully Convolutional Neural NetworksDec 18 2018Dec 19 2018The retinal vascular condition is a reliable biomarker of several ophthalmologic and cardiovascular diseases, so automatic vessel segmentation may be crucial to diagnose and monitor them. In this paper, we propose a novel method that combines the multiscale ... More
Spin Dependence of Heavy Quark FragmentationFeb 28 2007We propose that the non-perturbative fragmentation functions describing the transition from a heavy quark to a heavy meson is proportional to the square of the produced meson wave function at the origin. We analyze the effects of this proposal on the ... More
Dynamically correcting a CNOT gate for any systematic logical errorJul 15 2016We derive a set of composite pulse sequences that generate CNOT gates and correct all systematic errors within the logical subspace to arbitrary order. These sequences are applicable for any two-qubit interaction Hamiltonian, and make no assumptions about ... More
Spatial Product Partition ModelsApr 17 2015When modeling geostatistical or areal data, spatial structure is commonly accommodated via a covariance function for the former and a neighborhood structure for the latter. In both cases the resulting spatial structure is a consequence of implicit spatial ... More
Learning Attribute Representation for Human Activity RecognitionFeb 02 2018Attribute representations became relevant in image recognition and word spotting, providing support under the presence of unbalance and disjoint datasets. However, for human activity recognition using sequential data from on-body sensors, human-labeled ... More
A Discussion on the Transmission Conditions for Saturated Fluid Flow Through Porous Media With Fractal MicrostructureNov 26 2015May 29 2016We seek suitable exchange conditions for saturated fluid flow in a porous medium, where the interface of interest is a fractal microstructure embedded in the porous matrix. Two different deterministic models are introduced and rigorously analyzed. Also, ... More
Spectral and Localization Properties for the One-Dimensional Bernoulli Discrete Dirac OperatorMay 18 2005A 1D Dirac tight-binding model is considered and it is shown that its nonrelativistic limit is the 1D discrete Schr?odinger model. For random Bernoulli potentials taking two values (without correlations), for typical realizations and for all values of ... More
Coherence and Entanglement in a Stern-Gerlach experimentAug 24 2006We give a simple example of the tight connection between entanglement and coherence for pure bipartite systems showing the double role played by entanglement; it allows for the creation of superpositions of macroscopic objects but at the same time makes ... More
Reliability of digitized quantum annealing and the decay of entanglementNov 01 2016We performed a banged-digital-analog simulation of a quantum annealing protocol in a two-qubit Nuclear Magnetic Resonance (NMR) quantum computer. Our experimental simulation employed up to 235 Trotter steps, with more than 2000 gates (pulses), and we ... More
Optical and magnetic excitations of metal-encapsulating Si cages: A systematic study by time-dependent density functional theorySep 23 2013Systematic study of the optical and magnetic excitations of twelve MSi$_{12}$ and four MSi$_{10}$ transition metal encapsulating Si cages has been carried out by employing real time time-dependent density functional theory. Criteria for the choice of ... More
The Penna model for biological ageing on a lattice: spatial consequences of child-careNov 22 1999We introduce a square lattice into the Penna bit-string model for biological ageing and study the evolution of the spatial distribution of the population considering different strategies of child-care. Two of the strategies are related to the movements ... More
An Unusual Antagonistic Pleiotropy in the Penna Model for Biological AgeingFeb 21 2001We combine the Penna Model for biological aging, which is based on the mutation-accumulation theory, with a sort of antagonistic pleiotropy. We show that depending on how the pleiotropy is introduced, it is possible to reproduce both the humans mortality, ... More
Dimensionalities of Weak Solutions in Hydrogenic SystemsFeb 17 2006A close inspection on the 3D hydrogen atom Hamiltonian revealed formal eigenvectors often discarded in the literature. Although not in its domain, such eigenvectors belong to the Hilbert space, and so their time evolution is well defined. They are then ... More
Self-adjoint extensions of Coulomb systems in 1,2 and 3 dimensionsJun 17 2008We study the nonrelativistic quantum Coulomb hamiltonian (i.e., inverse of distance potential) in $R^n$, n = 1, 2, 3. We characterize their self-adjoint extensions and, in the unidimensional case, present a discussion of controversies in the literature, ... More
General class of vacuum Brans-Dicke wormholesJan 06 2010Mar 22 2010Recently, traversable wormhole geometries were constructed in the context of f(R) gravity. The latter is equivalent to a Brans-Dicke theory with a coupling parameter w=0, which is apparently excluded from the narrow interval, -3/2<w<-4/3, extensively ... More
Mean-field approximations for the restricted solid-on-solid growth modelsMar 23 2008We study models for surface growth with a wetting and a roughening transition using simple and pair mean-field approximations. The simple mean-field equations are solved exactly and they predict the roughening transition and the correct growth exponents ... More
On groups with cubic polynomial conditionsJan 20 2014May 11 2015Given a finitely generated subgroup G of a ring R we provide a finite subset of G such that if each element of this set satisfies some cubic polynomial equation in one variable over the center Z of R then the subring generated by G has finite Z-rank. ... More
Force and torque of a string on a pulleyJun 19 2017Every university introductory physics course considers the problem of Atwood's machine taking into account the mass of the pulley. In the usual treatment the tensions at the two ends of the string are offhandedly taken to act on the pulley and be responsible ... More
Dynamical Delocalization for the 1D Bernoulli Discrete Dirac OperatorJan 21 2005An 1D tight-binding version of the Dirac equation is considered; after checking that it recovers the usual discrete Schr?odinger equation in the nonrelativistic limit, it is found that for two-valued Bernoulli potentials the zero mass case presents absence ... More
Interference-Nulling Time-Reversal Beamforming for mm-Wave Massive MIMO in Multi-User Frequency-Selective Indoor ChannelsJun 16 2015Jun 18 2015Millimeter wave (mm-wave) and massive MIMO have been proposed for next generation wireless systems. However, there are many open problems for the implementation of those technologies. In particular, beamforming is necessary in mm-wave systems in order ... More
A Darcy-Brinkman Model of Fractures in Porous MediaNov 16 2016For a fully-coupled Darcy-Stokes system describing the exchange of fluid and stress balance across the interface between a saturated porous medium and an open very narrow channel, the limiting problem is characterized as the width of the channel converges ... More