Results for "Marc G. Bellemare"

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Off-Policy Deep Reinforcement Learning by Bootstrapping the Covariate ShiftJan 27 2019In this paper we revisit the method of off-policy corrections for reinforcement learning (COP-TD) pioneered by Hallak et al. (2017). Under this method, online updates to the value function are reweighted to avoid divergence issues typical of off-policy ... More
A Distributional Perspective on Reinforcement LearningJul 21 2017In this paper we argue for the fundamental importance of the value distribution: the distribution of the random return received by a reinforcement learning agent. This is in contrast to the common approach to reinforcement learning which models the expectation ... More
Count-Based Exploration with the Successor RepresentationJul 31 2018Jan 25 2019In this paper we introduce a simple approach for exploration in reinforcement learning (RL) that allows us to develop theoretically justified algorithms in the tabular case but that is also extendable to settings where function approximation is required. ... More
A Comparative Analysis of Expected and Distributional Reinforcement LearningJan 30 2019Since their introduction a year ago, distributional approaches to reinforcement learning (distributional RL) have produced strong results relative to the standard approach which models expected values (expected RL). However, aside from convergence guarantees, ... More
Q($λ$) with Off-Policy CorrectionsFeb 16 2016Aug 11 2016We propose and analyze an alternate approach to off-policy multi-step temporal difference learning, in which off-policy returns are corrected with the current Q-function in terms of rewards, rather than with the target policy in terms of transition probabilities. ... More
Distributional Reinforcement Learning with Quantile RegressionOct 27 2017In reinforcement learning an agent interacts with the environment by taking actions and observing the next state and reward. When sampled probabilistically, these state transitions, rewards, and actions can all induce randomness in the observed long-term ... More
Safe and Efficient Off-Policy Reinforcement LearningJun 08 2016In this work, we take a fresh look at some old and new algorithms for off-policy, return-based reinforcement learning. Expressing these in a common form, we derive a novel algorithm, Retrace($\lambda$), with three desired properties: (1) low variance; ... More
The Arcade Learning Environment: An Evaluation Platform for General AgentsJul 19 2012Jun 21 2013In this article we introduce the Arcade Learning Environment (ALE): both a challenge problem and a platform and methodology for evaluating the development of general, domain-independent AI technology. ALE provides an interface to hundreds of Atari 2600 ... More
Approximate Exploration through State AbstractionAug 29 2018Jan 24 2019Although exploration in reinforcement learning is well understood from a theoretical point of view, provably correct methods remain impractical. In this paper we study the interplay between exploration and approximation, what we call approximate exploration. ... More
Safe and Efficient Off-Policy Reinforcement LearningJun 08 2016Nov 07 2016In this work, we take a fresh look at some old and new algorithms for off-policy, return-based reinforcement learning. Expressing these in a common form, we derive a novel algorithm, Retrace($\lambda$), with three desired properties: (1) it has low variance; ... More
Unifying Count-Based Exploration and Intrinsic MotivationJun 06 2016We consider an agent's uncertainty about its environment and the problem of generalizing this uncertainty across observations. Specifically, we focus on the problem of exploration in non-tabular reinforcement learning. Drawing inspiration from the intrinsic ... More
Revisiting the Arcade Learning Environment: Evaluation Protocols and Open Problems for General AgentsSep 18 2017Dec 01 2017The Arcade Learning Environment (ALE) is an evaluation platform that poses the challenge of building AI agents with general competency across dozens of Atari 2600 games. It supports a variety of different problem settings and it has been receiving increasing ... More
Shaping the Narrative Arc: An Information-Theoretic Approach to Collaborative DialogueJan 31 2019We consider the problem of designing an artificial agent capable of interacting with humans in collaborative dialogue to produce creative, engaging narratives. In this task, the goal is to establish universe details, and to collaborate on an interesting ... More
Increasing the Action Gap: New Operators for Reinforcement LearningDec 15 2015This paper introduces new optimality-preserving operators on Q-functions. We first describe an operator for tabular representations, the consistent Bellman operator, which incorporates a notion of local policy consistency. We show that this local consistency ... More
An Analysis of Categorical Distributional Reinforcement LearningFeb 22 2018Distributional approaches to value-based reinforcement learning model the entire distribution of returns, rather than just their expected values, and have recently been shown to yield state-of-the-art empirical performance. This was demonstrated by the ... More
Compress and ControlNov 19 2014This paper describes a new information-theoretic policy evaluation technique for reinforcement learning. This technique converts any compression or density model into a corresponding estimate of value. Under appropriate stationarity and ergodicity conditions, ... More
An Introduction to Deep Reinforcement LearningNov 30 2018Dec 03 2018Deep reinforcement learning is the combination of reinforcement learning (RL) and deep learning. This field of research has been able to solve a wide range of complex decision-making tasks that were previously out of reach for a machine. Thus, deep RL ... More
The Value Function Polytope in Reinforcement LearningJan 31 2019Feb 15 2019We establish geometric and topological properties of the space of value functions in finite state-action Markov decision processes. Our main contribution is the characterization of the nature of its shape: a general polytope (Aigner et al., 2010). To ... More
The Value Function Polytope in Reinforcement LearningJan 31 2019We establish geometric and topological properties of the space of value functions in finite state-action Markov decision processes. Our main contribution is the characterization of the nature of its shape: a general polytope (Aigner et al., 2010). To ... More
Distributional reinforcement learning with linear function approximationFeb 08 2019Despite many algorithmic advances, our theoretical understanding of practical distributional reinforcement learning methods remains limited. One exception is Rowland et al. (2018)'s analysis of the C51 algorithm in terms of the Cram\'er distance, but ... More
Dopamine: A Research Framework for Deep Reinforcement LearningDec 14 2018Deep reinforcement learning (deep RL) research has grown significantly in recent years. A number of software offerings now exist that provide stable, comprehensive implementations for benchmarking. At the same time, recent deep RL research has become ... More
Unifying Count-Based Exploration and Intrinsic MotivationJun 06 2016Nov 07 2016We consider an agent's uncertainty about its environment and the problem of generalizing this uncertainty across observations. Specifically, we focus on the problem of exploration in non-tabular reinforcement learning. Drawing inspiration from the intrinsic ... More
A Geometric Perspective on Optimal Representations for Reinforcement LearningJan 31 2019This paper proposes a new approach to representation learning based on geometric properties of the space of value functions. We study a two-part approximation of the value function: a nonlinear map from states to vectors, or representation, followed by ... More
The Hanabi Challenge: A New Frontier for AI ResearchFeb 01 2019From the early days of computing, games have been important testbeds for studying how well machines can do sophisticated decision making. In recent years, machine learning has made dramatic advances with artificial agents reaching superhuman performance ... More
The Barbados 2018 List of Open Issues in Continual LearningNov 16 2018We want to make progress toward artificial general intelligence, namely general-purpose agents that autonomously learn how to competently act in complex environments. The purpose of this report is to sketch a research outline, share some of the most important ... More
An Atari Model Zoo for Analyzing, Visualizing, and Comparing Deep Reinforcement Learning AgentsDec 17 2018Much human and computational effort has aimed to improve how deep reinforcement learning algorithms perform on benchmarks such as the Atari Learning Environment. Comparatively less effort has focused on understanding what has been learned by such methods, ... More
Asymptotic-numerical study of supersensitivity for generalized Burgers equationsAug 11 1999This article addresses some asymptotic and numerical issues related to the solution of Burgers' equation, $-\epsilon u_{xx} + u_t + u u_x = 0$ on $(-1,1)$, subject to the boundary conditions $u(-1) = 1 + \delta$, $u(1) = -1$, and its generalization to ... More
Cross-Covariance Functions for Multivariate GeostatisticsJul 29 2015Continuously indexed datasets with multiple variables have become ubiquitous in the geophysical, ecological, environmental and climate sciences, and pose substantial analysis challenges to scientists and statisticians. For many years, scientists developed ... More
Non-Stationary Dependence Structures for Spatial ExtremesNov 12 2014Feb 19 2016Max-stable processes are natural models for spatial extremes because they provide suitable asymptotic approximations to the distribution of maxima of random fields. In the recent past, several parametric families of stationary max-stable models have been ... More
A Copula-Based Linear Model of Coregionalization for Non-Gaussian Multivariate Spatial DataMar 12 2016We propose a new copula model for replicated multivariate spatial data. Unlike classical models that assume multivariate normality of the data, the proposed copula is based on the assumption that some factors exist that affect the joint spatial dependence ... More
Rejoinder of ``Cross-Covariance Functions for Multivariate Geostatistics''Jul 30 2015Rejoinder of ``Cross-Covariance Functions for Multivariate Geostatistics'' by Genton and Kleiber [arXiv:1507.08017].
Discussion of "Breakdown and groups" by P. L. Davies and U. GatherAug 25 2005Discussion of ``Breakdown and groups'' by P. L. Davies and U. Gather [math.ST/0508497]
Interdependent networks: the fragility of controlSep 26 2013Recent work in the area of interdependent networks has focused on interactions between two systems of the same type. However, an important and ubiquitous class of systems are those involving monitoring and control, an example of interdependence between ... More
Transport on coupled spatial networksMay 12 2012Sep 28 2012Transport processes on spatial networks are representative of a broad class of real world systems which, rather than being independent, are typically interdependent. We propose a measure of utility to capture key features that arise when such systems ... More
Efficient Maximum Approximated Likelihood Inference for Tukey's g-and-h DistributionJun 02 2015Tukey's $g$-and-$h$ distribution has been a powerful tool for data exploration and modeling since its introduction. However, two long standing challenges associated with this distribution family have remained unsolved until this day: how to find an optimal ... More
Diminishing functionals for nonclassical entropy solutions selected by kinetic relationsDec 21 2008We consider nonclassical entropy solutions to scalar conservation laws with concave-convex flux functions, whose set of left- and right-hand admissible states across undercompressive shocks is selected by a kinetic function \phi. We introduce a new definition ... More
Odd-Parity Bipolar Spherical HarmonicsSep 13 2011Nov 18 2011Bipolar spherical harmonics (BiPoSHs) provide a general formalism for quantifying departures in the cosmic microwave background (CMB) from statistical isotropy (SI) and from Gaussianity. However, prior work has focused only on BiPoSHs with even parity. ... More
Revisiting the method of characteristics via a convex hull algorithmSep 01 2014We revisit the method of characteristics for shock wave solutions to nonlinear hyperbolic problems and we describe a novel numerical algorithm - the convex hull algorithm (CHA) - in order to compute, both, entropy dissipative solutions (satisfying all ... More
An algorithm (CoDeFi) for the curse of dimensionality in financeJun 30 2016We present a new algorithm (CoDeFi) to tackle the Curse Of Dimensionality In Finance and deal with a broad class of partial differential equations including the Kolmogorov equations as, for instance, the Black and Scholes equations. As a main feature, ... More
Bayesian linear regression with skew-symmetric error distributions with applications to survival analysisJan 10 2016We study Bayesian linear regression models with skew-symmetric scale mixtures of normal error distributions. These kinds of models can be used to capture departures from the usual assumption of normality of the errors in terms of heavy tails and asymmetry. ... More
On the asymptotic joint distribution of sample space--time covariance estimatorsMar 14 2008We study the asymptotic joint distribution of sample space--time covariance estimators of strictly stationary random fields. We do this without any marginal or joint distributional assumptions other than mild moment and mixing conditions. We consider ... More
An algorithm (CoDeFi) for overcoming the curse of dimensionality in mathematical financeJun 30 2016Oct 06 2016We present an algorithm (CoDeFi) which overcomes the curse of dimensionality (CoD) in scientific computations and, especially, in mathematical finance (Fi). Our method applies a broad class of partial differential equations such as Kolmogorov-type equations ... More
Physical properties of a very diffuse HI structure at high Galactic latitudeFeb 28 2007The main goal of this analysis is to present a new method to estimate the physical properties of diffuse cloud of atomic hydrogen observed at high Galactic latitude. This method, based on a comparison of the observations with fractional Brownian motion ... More
Factor Copula Models for Replicated Spatial DataNov 10 2015Jul 10 2016We propose a new copula model that can be used with replicated spatial data. Unlike the multivariate normal copula, the proposed copula is based on the assumption that a common factor exists and affects the joint dependence of all measurements of the ... More
Diagonal Likelihood Ratio Test for Equality of Mean Vectors in High-Dimensional DataOct 27 2017Sep 24 2018We propose a likelihood ratio test framework for testing normal mean vectors in high-dimensional data under two common scenarios: the one-sample test and the two-sample test with equal covariance matrices. We derive the test statistics under the assumption ... More
A Multi-Resolution Spatial Model for Large Datasets Based on the Skew-t DistributionDec 06 2017Large, non-Gaussian spatial datasets pose a considerable modeling challenge as the dependence structure implied by the model needs to be captured at different scales, while retaining feasible inference. Skew-normal and skew-t distributions have only recently ... More
Lexical Functions and Machine TranslationOct 20 1994This paper discusses the lexicographical concept of lexical functions and their potential exploitation in the development of a machine translation lexicon designed to handle collocations.
Comment on "Logarithmic Oscillators: Ideal Hamiltonian Thermostats" [arXiv 1203.5968]Jun 01 2012Jan 29 2013Campisi, Zhan, Talkner and H\"anggi have recently proposed a novel Hamiltonian thermostat which they claim may be used both in simulations and experiments [arXiv:1203.5968v4]. We show, however, that this is not possible due to the length and time scales ... More
A Multi-Resolution Spatio-Temporal Model for Brain Activation and Connectivity in fMRI DataFeb 07 2016Jun 15 2016Functional Magnetic Resonance Imaging (fMRI) is a primary modality for studying brain activity. Modeling spatial dependence of imaging data at different scales is one of the main challenges of contemporary neuroimaging, and it could allow for accurate ... More
Bayesian Modeling of Air Pollution Extremes Using Nested Multivariate Max-Stable ProcessesMar 18 2018Capturing the potentially strong dependence among the peak concentrations of multiple air pollutants across a spatial region is crucial for assessing the related public health risks. In order to investigate the multivariate spatial dependence properties ... More
The connectivity at infinity of a manifold and $L^{q,p}$-Sobolev inequalitiesJul 11 2010May 16 2013The purpose of this paper is to give a self-contained proof that a complete manifold with more than one end never supports an $L^{q,p}$-Sobolev inequality ($2 \leq p$, $q\leq p^{*}$), provided the negative part of its Ricci tensor is small (in a suitable ... More
Asymptotic analysis of the Guyer-Krumhansl-Stefan model for nanoscale solidificationApr 17 2018Nanoscale solidification is becoming increasingly relevant in applications involving ultra-fast freezing processes and nanotechnology. However, thermal transport on the nanoscale is driven by infrequent collisions between thermal energy carriers known ... More
Modelling ultra-fast nanoparticle melting with the Maxwell-Cattaneo equationJun 06 2018Nov 13 2018The role of thermal relaxation in nanoparticle melting is studied using a mathematical model based on the Maxwell--Cattaneo equation for heat conduction. The model is formulated in terms of a two-phase Stefan problem. We consider the cases of the temperature ... More
Mineral bridges in nacre revisitedJul 20 2012We confirm with high-resolution techniques the existence of mineral bridges between superposed nacre tablets. In the towered nacre of both gastropods and the cephalopod Nautilus there are large bridges aligned along the tower axes, corresponding to gaps ... More
Gravitational-wave phasing for low-eccentricity inspiralling compact binaries to 3PN orderMay 01 2016Jun 29 2016[abridged] Although gravitational radiation causes inspiralling compact binaries to circularize, a variety of astrophysical scenarios suggest that binaries might have small but nonnegligible orbital eccentricities when they enter the low-frequency bands ... More
Stripes in Doped Antiferromagnets: Single-Particle Spectral WeightMay 26 2000Sep 20 2000Recent photoemission (ARPES) experiments on cuprate superconductors provide important guidelines for a theory of electronic excitations in the stripe phase. Using a cluster perturbation theory, where short-distance effects are accounted for by exact cluster ... More
Reconstructing dynamical networks via feature rankingFeb 11 2019Empirical data on real complex systems are becoming increasingly available. Parallel to this is the need for new methods of reconstructing (inferring) the topology of networks from time-resolved observations of their node-dynamics. The methods based on ... More
Evolution of the stripe phase as a function of doping from a theoretical analysis of angle-resolved photoemission dataMar 01 2001Mar 20 2001By comparing single-particle spectral functions of t-J and Hubbard models with recent angle-resolved photoemission (ARPES) results for LSCO and Nd-LSCO, we can decide where holes go as a function of doping, and more specifically, which type of stripe ... More
The Velocity Field from Type Ia Supernovae Matches the Gravity Field from Galaxy SurveysJul 24 1997We compare the peculiar velocities of nearby SNe Ia with those predicted by the gravity fields of full sky galaxy catalogs. The method provides a powerful test of the gravitational instability paradigm and strong constraints on the density parameter beta ... More
Rippled nanocarbons from periodic arrangements of reordered bivacancies in graphene or SWCNTsJan 20 2012We report on various nanocarbons formed from a unique structural pattern containing two pentagons, three hexagons and two heptagons, resulting from local rearrange- ments around a divacancy in pristine graphene or nanotubes. This defect can be inserted ... More
Non-Gaussianity from Self-Ordering Scalar FieldsMar 02 2010The Universe may harbor relics of the post-inflationary epoch in the form of a network of self-ordered scalar fields. Such fossils, while consistent with current cosmological data at trace levels, may leave too weak an imprint on the cosmic microwave ... More
Interrelation of Superconducting and Antiferromagnetic Gaps in High-Tc Compounds: a Test Case for a Microscopic TheoryAug 12 1999Recent angle resolved photoemission (ARPES) data, which found evidence for a d-wave-like modulation of the antiferromagnetic gap, suggest an intimate interrelation between the antiferromagnetic insulator and the superconductor with its d-wave gap. This ... More
A Non-Gaussian Spatio-Temporal Model for Daily Wind Speeds Based on a Multivariate Skew-t DistributionMar 13 2017Feb 13 2019Facing increasing domestic energy consumption from population growth and industrialization, Saudi Arabia is aiming to reduce its reliance on fossil fuels and to broaden its energy mix by expanding investment in renewable energy sources, including wind ... More
Incorporating geostrophic wind information for improved space-time short-term wind speed forecastingDec 05 2014Accurate short-term wind speed forecasting is needed for the rapid development and efficient operation of wind energy resources. This is, however, a very challenging problem. Although on the large scale, the wind speed is related to atmospheric pressure, ... More
Likelihood estimators for multivariate extremesNov 13 2014Jun 16 2015The main approach to inference for multivariate extremes consists in approximating the joint upper tail of the observations by a parametric family arising in the limit for extreme events. The latter may be expressed in terms of componentwise maxima, high ... More
Interrelation of Superconducting and Antiferromagnetic Gaps in High-Tc Compounds: a Test Case for the SO(5) TheoryDec 09 1999Jul 17 2000Recent angle resolved photoemission data, which found evidence for a d-wave-like modulation of the antiferromagnetic gap, suggest an intimate interrelation between the antiferromagnetic insulator and the superconductor with its d-wave gap. It is shown ... More
Superconducting Pb stripline resonators in parallel magnetic field and their application for microwave spectroscopyMay 13 2016Oct 10 2016Planar superconducting microwave resonators are key elements in a variety of technical applications and also act as sensitive probes for microwave spectroscopy of various materials of interest. Here superconducting Pb is a suitable material as a basis ... More
Non-local energetics of random heterogeneous latticesMar 16 2010Nov 09 2010In this paper, we study the mechanics of statistically non-uniform two-phase elastic discrete structures. In particular, following the methodology proposed in (Luciano and Willis, Journal of the Mechanics and Physics of Solids 53, 1505-1522, 2005), energetic ... More
Dark-Matter Decays and Self-Gravitating HalosMar 01 2010May 26 2010We consider models in which a dark-matter particle decays to a slightly less massive daughter particle and a noninteracting massless particle. The decay gives the daughter particle a small velocity kick. Self-gravitating dark-matter halos that have a ... More
Fabrication of High Aspect Ratio Micro-Penning-Malmberg Gold Plated Silicon Trap ArraysJul 09 2013Acquiring a portable high density charged particles trap might consist of an array of micro-Penning-Malmberg traps (microtraps) with substantially lower end barriers potential than conventional Penning-Malmberg traps [1]. We report on the progress of ... More
Dark energy from the string axiverseSep 01 2014Sep 22 2014String theories suggest the existence of a plethora of axion-like fields with masses spread over a huge number of decades. Here we show that these ideas lend themselves to a model of quintessence with no super-Planckian field excursions and in which all ... More
Multi-Level Restricted Maximum Likelihood Covariance Estimation and Kriging for Large Non-Gridded Spatial DatasetsApr 01 2015Mar 28 2016We develop a multi-level restricted Gaussian maximum likelihood method for estimating the covariance function parameters and computing the best unbiased predictor. Our approach produces a new set of multi-level contrasts where the deterministic parameters ... More
Functional Outlier Detection and Taxonomy by Sequential TransformationsAug 16 2018Functional data analysis can be seriously impaired by abnormal observations, which can be classified as either magnitude or shape outliers based on their way of deviating from the bulk of data. Identifying magnitude outliers is relatively easy, while ... More
A Stochastic Generator of Global Monthly Wind Energy with Tukey $g$-and-$h$ Autoregressive ProcessesNov 10 2017Quantifying the uncertainty of wind energy potential from climate models is a very time-consuming task and requires a considerable amount of computational resources. A statistical model trained on a small set of runs can act as a stochastic approximation ... More
Likelihood Approximation With Hierarchical Matrices For Large Spatial DatasetsSep 08 2017Sep 12 2018We use available measurements to estimate the unknown parameters (variance, smoothness parameter, and covariance length) of a covariance function by maximizing the joint Gaussian log-likelihood function. To overcome cubic complexity in the linear algebra, ... More
On the Cartesian Skeleton and the Factorization of the Strong Product of DigraphsJan 20 2014The three standard products (the Cartesian, the direct and the strong product) of undirected graphs have been wellinvestigated, unique prime factor decomposition (PFD) are known and polynomial time algorithms have been established for determining the ... More
Effective thermal conductivity of rectangular nanowires based on phonon hydrodynamicsMay 31 2018Jun 03 2018A mathematical model is presented for thermal transport in nanowires with rectangular cross sections. Expressions for the effective thermal conductivity of the nanowire across a range of temperatures and cross-sectional aspect ratios are obtained by solving ... More
Mechanics of dislocation pile-ups: A unification of scaling regimesAug 28 2012This paper unravels the problem of an idealised pile-up of n infinite, equi-spaced walls of edge dislocations at equilibrium. We define a dimensionless parameter that depends on the geometric, constitutive and loading parameters of the problem, and we ... More
Evidence for X-ray emission from a large-scale filament of galaxies ?Nov 15 1999Cosmological simulations predict that a large fraction of the baryonic mass of the Universe exists as 10^5-10^7 K diffuse, X-ray emitting gas, tracing low density filament and sheet-like structures exterior to massive clusters of galaxies. If present, ... More
Spatial Blind Source SeparationDec 21 2018Recently a blind source separation model was suggested for multivariate spatial data together with an estimator based on the simultaneous diagonalization of two scatter matrices. The asymptotic properties of this estimator are derived here and a new estimator, ... More
Wind Power Persistence is Governed by SuperstatisticOct 12 2018Oct 16 2018Mitigating climate change demands a transition towards renewable electricity generation, with wind power being a particularly promising technology. Long periods either of high or of low wind therefore essentially define the necessary amount of storage ... More
Retrieving intracycle interference in angular-resolved laser-assisted photoemission from argonAug 14 2018We report on a combined experimental and theoretical study of XUV ionization of atomic argon in the presence of a near-infrared laser field. The resulting energy- and angle- resolved photoemission spectra have been described in the literature as interferences ... More
Comparison of near-interface traps in Al$_2$O$_3$/4H-SiC and Al$_2$O$_3$/SiO$_2$/4H-SiC structuresOct 03 2006Aluminum oxide (Al2O3) has been grown by atomic layer deposition on n-type 4H-SiC with and without a thin silicon dioxide (SiO2) intermediate layer. By means of Capacitance Voltage and Thermal Dielectric Relaxation Current measurements, the interface ... More
A Detailed Study of Giants and Horizontal Branch Stars in M68: Atmospheric Parameters and Chemical AbundancesMay 13 2015In this paper, we present a detailed high-resolution spectroscopic study of post main sequence stars in the Globular Cluster M68. Our sample, which covers a range of 4000 K in $T_{eff}$, and 3.5 dex in $log(g)$, is comprised of members from the red giant, ... More
Disorder, pseudospins, and backscattering in carbon nanotubesJun 04 1999We address the effects of disorder on the conducting properties of metal and semiconducting carbon nanotubes. Experimentally, the mean free path is found to be much larger in metallic tubes than in doped semiconducting tubes. We show that this result ... More
Spin splitting and even-odd effects in carbon nanotubesApr 15 1998The level spectrum of a single-walled carbon nanotube rope, studied by transport spectroscopy, shows Zeeman splitting in a magnetic field parallel to the tube axis. The pattern of splittings implies that the spin of the ground state alternates by 1/2 ... More
Proper definition and evolution of generalized transverse momentum distributionsFeb 22 2016Jun 10 2016We consider one of the most fundamental sets of hadronic matrix elements, namely the generalized transverse momentum distributions (GTMDs), and argue that their existing definitions lack proper evolution properties. By exploiting the similarity of GTMDs ... More
Robust Recognition of Simultaneous Speech By a Mobile RobotFeb 20 2016This paper describes a system that gives a mobile robot the ability to perform automatic speech recognition with simultaneous speakers. A microphone array is used along with a real-time implementation of Geometric Source Separation and a post-filter that ... More
Ultra-Stretchable Interconnects for High-Density Stretchable ElectronicsSep 13 2017The exciting field of stretchable electronics (SE) promises numerous novel applications, particularly in-body and medical diagnostics devices. However, future advanced SE miniature devices will require high-density, extremely stretchable interconnects ... More
SR-Clustering: Semantic Regularized Clustering for Egocentric Photo Streams SegmentationDec 22 2015Oct 17 2016While wearable cameras are becoming increasingly popular, locating relevant information in large unstructured collections of egocentric images is still a tedious and time consuming processes. This paper addresses the problem of organizing egocentric photo ... More
Constraints on Decaying Dark MatterNov 22 2010We explore a dark-matter model in which there are two dark-matter species nearly degenerate in mass, with epsilon = Delta M/M << 1. The heavier particle undergoes two-body decay with a half-life tau, to the lighter dark-matter particle and a noninteracting ... More
Extracting Atoms on Demand with LasersDec 23 2004We propose a scheme that allows to coherently extract cold atoms from a reservoir in a deterministic way. The transfer is achieved by means of radiation pulses coupling two atomic states which are object to different trapping conditions. A particular ... More
ExaGeoStat: A High Performance Unified Software for Geostatistics on Manycore SystemsAug 09 2017Jun 22 2018We present ExaGeoStat, a high performance framework for geospatial statistics in climate and environment modeling. In contrast to simulation based on partial differential equations derived from first-principles modeling, ExaGeoStat employs a statistical ... More
Electronic structure based descriptor for characterizing local atomic environmentsOct 08 2018A quantitative descriptor of local atomic environments is often required for the analysis of atomistic data. Descriptors of the local atomic environment ideally provide physically and chemically intuitive insight. This requires descriptors that are low-dimensional ... More
Using Automatic Differentiation as a General Framework for Ptychographic ReconstructionFeb 08 2019Coherent diffraction imaging methods enable imaging beyond lens-imposed resolution limits. In these methods, the object can be recovered by minimizing an error metric that quantifies the difference between diffraction patterns as observed, and those calculated ... More
Multi$^{\mathbf{3}}$Net: Segmenting Flooded Buildings via Fusion of Multiresolution, Multisensor, and Multitemporal Satellite ImageryDec 05 2018We propose a novel approach for rapid segmentation of flooded buildings by fusing multiresolution, multisensor, and multitemporal satellite imagery in a convolutional neural network. Our model significantly expedites the generation of satellite imagery-based ... More
On nomenclature for, and the relative merits of, two formulations of skew distributionsFeb 21 2014Dec 03 2015We examine some distributions used extensively within the model-based clustering literature in recent years, paying special attention to} claims that have been made about their relative efficacy. Theoretical arguments are provided as well as real data ... More
Simulation studies of the behavior of positrons in a microtrap with long aspect ratioDec 31 2012Jul 09 2013The charged particles storage capacity of microtraps (micro-Penning-Malmberg traps) with large length to radius aspect ratios and radii of the order of tens of microns was explored. Simulation studies of the motions of charged particles were conducted ... More
Nebular dead zone effects on the D/H ratio in chondrites and cometsAug 02 2015Comets and chondrites show non-monotonic behaviour of their Deuterium to Hydrogen (D/H) ratio as a function of their formation location from the Sun. This is difficult to explain with a classical protoplanetary disk model that has a decreasing temperature ... More
Establishing the level of cylindrical rotation in Boxy/Peanut bulgesNov 17 2015We present SAURON integral-field observations of a sample of 12 mid to high-inclination disk galaxies, to unveil hidden bars on the basis of their kinematics, i.e., the correlation between velocity and h3 profiles, and to establish their degree of cylindrical ... More