Results for "Kris M. Kitani"

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Generative Hybrid Representations for Activity Forecasting with No-Regret LearningApr 12 2019Automatically reasoning about future human behaviors is a difficult problem with significant practical applications to assistive systems. Part of this difficulty stems from learning systems' inability to represent all kinds of behaviors. Some behaviors, ... More
Forecasting Interactive Dynamics of Pedestrians with Fictitious PlayApr 05 2016Mar 28 2017We develop predictive models of pedestrian dynamics by encoding the coupled nature of multi-pedestrian interaction using game theory, and deep learning-based visual analysis to estimate person-specific behavior parameters. Building predictive models for ... More
First-Person Activity Forecasting with Online Inverse Reinforcement LearningDec 22 2016Aug 06 2017We address the problem of incrementally modeling and forecasting long-term goals of a first-person camera wearer: what the user will do, where they will go, and what goal they seek. In contrast to prior work in trajectory forecasting, our algorithm, DARKO, ... More
Learning Action Maps of Large Environments via First-Person VisionMay 05 2016When people observe and interact with physical spaces, they are able to associate functionality to regions in the environment. Our goal is to automate dense functional understanding of large spaces by leveraging sparse activity demonstrations recorded ... More
Going Deeper into First-Person Activity RecognitionMay 12 2016We bring together ideas from recent work on feature design for egocentric action recognition under one framework by exploring the use of deep convolutional neural networks (CNN). Recent work has shown that features such as hand appearance, object attributes, ... More
Inverse Reinforcement Learning with Conditional Choice ProbabilitiesSep 22 2017We make an important connection to existing results in econometrics to describe an alternative formulation of inverse reinforcement learning (IRL). In particular, we describe an algorithm using Conditional Choice Probabilities (CCP), which are maximum ... More
Ego-Surfing: Person Localization in First-Person Videos Using Ego-Motion SignaturesJun 15 2016Nov 29 2017We envision a future time when wearable cameras are worn by the masses and recording first-person point-of-view videos of everyday life. While these cameras can enable new assistive technologies and novel research challenges, they also raise serious privacy ... More
VADRA: Visual Adversarial Domain Randomization and AugmentationDec 03 2018We address the issue of learning from synthetic domain randomized data effectively. While previous works have showcased domain randomization as an effective learning approach, it lacks in challenging the learner and wastes valuable compute on generating ... More
Deep Supervised Hashing with Triplet LabelsDec 12 2016Hashing is one of the most popular and powerful approximate nearest neighbor search techniques for large-scale image retrieval. Most traditional hashing methods first represent images as off-the-shelf visual features and then produce hashing codes in ... More
Ego-Surfing First-Person VideosJun 15 2016We envision a future time when wearable cameras are worn by the masses, recording first-person point-of-view (POV) videos of everyday life. While these cameras can enable new assistive technologies and novel research challenges, they also raise serious ... More
Learnable Embedding Space for Efficient Neural Architecture CompressionFeb 01 2019We propose a method to incrementally learn an embedding space over the domain of network architectures, to enable the careful selection of architectures for evaluation during compressed architecture search. Given a teacher network, we search for a compressed ... More
Domain Randomization for Scene-Specific Car Detection and Pose EstimationNov 14 2018We address the issue of domain gap when making use of synthetic data to train a scene-specific object detector and pose estimator. While previous works have shown that the constraints of learning a scene-specific model can be leveraged to create geometrically ... More
Error Correction Maximization for Deep Image HashingAug 06 2018We propose to use the concept of the Hamming bound to derive the optimal criteria for learning hash codes with a deep network. In particular, when the number of binary hash codes (typically the number of image categories) and code length are known, it ... More
Contextual Visual SimilarityDec 08 2016Measuring visual similarity is critical for image understanding. But what makes two images similar? Most existing work on visual similarity assumes that images are similar because they contain the same object instance or category. However, the reason ... More
Monocular 3D Object Detection with Pseudo-LiDAR Point CloudMar 23 2019Monocular 3D scene understanding tasks, such as object size estimation, heading angle estimation and 3D localization, is challenging. Successful modern day methods for 3D scene understanding require the use of a 3D sensor such as a depth camera, a stereo ... More
Privacy-Preserving Visual Learning Using Doubly Permuted Homomorphic EncryptionApr 07 2017Jul 28 2017We propose a privacy-preserving framework for learning visual classifiers by leveraging distributed private image data. This framework is designed to aggregate multiple classifiers updated locally using private data and to ensure that no private information ... More
Monocular 3D Object Detection with Pseudo-LiDAR Point CloudMar 23 2019Mar 31 2019Monocular 3D scene understanding tasks, such as object size estimation, heading angle estimation and 3D localization, is challenging. Successful modern day methods for 3D scene understanding require the use of a 3D sensor such as a depth camera, a stereo ... More
N2N Learning: Network to Network Compression via Policy Gradient Reinforcement LearningSep 18 2017Dec 17 2017While bigger and deeper neural network architectures continue to advance the state-of-the-art for many computer vision tasks, real-world adoption of these networks is impeded by hardware and speed constraints. Conventional model compression methods attempt ... More
Gesture-based Bootstrapping for Egocentric Hand SegmentationDec 09 2016Jun 11 2018Accurately identifying hands in images is a key sub-task for human activity understanding with wearable first-person point-of-view cameras. Traditional hand segmentation approaches rely on a large corpus of manually labeled data to generate robust hand ... More
Future Near-Collision Prediction from Monocular Video: Feasibility, Dataset, and ChallengesMar 21 2019We explore the possibility of using a single monocular camera to forecast the time to collision between a suitcase-shaped robot being pushed by its user and other nearby pedestrians. We develop a purely image-based deep learning approach that directly ... More
In Teacher We Trust: Learning Compressed Models for Pedestrian DetectionDec 01 2016Deep convolutional neural networks continue to advance the state-of-the-art in many domains as they grow bigger and more complex. It has been observed that many of the parameters of a large network are redundant, allowing for the possibility of learning ... More
ADA: A Game-Theoretic Perspective on Data Augmentation for Object DetectionOct 21 2017Dec 12 2017The use of random perturbations of ground truth data, such as random translation or scaling of bounding boxes, is a common heuristic used for data augmentation that has been shown to prevent overfitting and improve generalization. Since the design of ... More
Directed-Info GAIL: Learning Hierarchical Policies from Unsegmented Demonstrations using Directed InformationSep 29 2018Mar 12 2019The use of imitation learning to learn a single policy for a complex task that has multiple modes or hierarchical structure can be challenging. In fact, previous work has shown that when the modes are known, learning separate policies for each mode or ... More
Directed-Info GAIL: Learning Hierarchical Policies from Unsegmented Demonstrations using Directed InformationSep 29 2018The use of imitation learning to learn a single policy for a complex task that has multiple modes or hierarchical structure can be challenging. In fact, previous work has shown that when the modes are known, learning separate policies for each mode or ... More
Learning Neural Parsers with Deterministic Differentiable Imitation LearningJun 20 2018Sep 19 2018We explore the problem of learning to decompose spatial tasks into segments, as exemplified by the problem of a painting robot covering a large object. Inspired by the ability of classical decision tree algorithms to construct structured partitions of ... More
Efficient K-Shot Learning with Regularized Deep NetworksOct 06 2017Feature representations from pre-trained deep neural networks have been known to exhibit excellent generalization and utility across a variety of related tasks. Fine-tuning is by far the simplest and most widely used approach that seeks to exploit and ... More
Eta Carinae's Declining Outflow Seen in the UV, 2002-2015Apr 19 2018Existing HST UV data offer many previously neglected clues to eta Car's behavior since 2000. Here we examine a subset of observations with diverse results. (1) The star's rapid change of state is confirmed by major changes in UV absorption lines, circumstellar ... More
A Game-Theoretic Approach to Multi-Pedestrian Activity ForecastingApr 05 2016May 09 2016We develop predictive models of pedestrian dynamics by encoding the coupled nature of multi-pedestrian interaction using game theory, and deep learning-based visual analysis to estimate person-specific behavior parameters. Building predictive models for ... More
Human-Interactive Subgoal Supervision for Efficient Inverse Reinforcement LearningJun 22 2018Humans are able to understand and perform complex tasks by strategically structuring the tasks into incremental steps or subgoals. For a robot attempting to learn to perform a sequential task with critical subgoal states, such states can provide a natural ... More
HARMONIC: A Multimodal Dataset of Assistive Human-Robot CollaborationJul 30 2018We present HARMONIC, a large multi-modal dataset of human interactions in a shared autonomy setting. The dataset provides human, robot, and environment data streams from twenty-four people engaged in an assistive eating task with a 6 degree-of-freedom ... More
GroundNet: Segmentation-Aware Monocular Ground Plane Estimation with Geometric ConsistencyNov 17 2018We focus on the problem of estimating the orientation of the ground plane with respect to a mobile monocular camera platform (e.g., ground robot, wearable camera, assistive robotic platform). To address this problem, we formulate the ground plane estimation ... More
Understanding hand-object manipulation by modeling the contextual relationship between actions, grasp types and object attributesJul 22 2018This paper proposes a novel method for understanding daily hand-object manipulation by developing computer vision-based techniques. Specifically, we focus on recognizing hand grasp types, object attributes and manipulation actions within an unified framework ... More
Modeling Social Group Communication with Multi-Agent Imitation LearningMar 04 2019In crowded social scenarios with a myriad of external stimuli, human brains exhibit a natural ability to filter out irrelevant information and narrowly focus their attention. In the midst of multiple groups of people, humans use such sensory gating to ... More
Personalized Dynamics Models for Adaptive Assistive Navigation SystemsApr 11 2018Oct 08 2018Consider an assistive system that guides visually impaired users through speech and haptic feedback to their destination. Existing robotic and ubiquitous navigation technologies (e.g., portable, ground, or wearable systems) often operate in a generic, ... More
Luminous and Variable Stars in M31 and M33 V. The Upper HR DiagramJul 06 2017We present HR Diagrams for the massive star populations in M31 and M33 including several different types of emission-line stars: the confirmed Luminous Blue Variables (LBVs), candidate LBVs, B[e] supergiants and the warm hypergiants. We estimate their ... More
Predictive-State Decoders: Encoding the Future into Recurrent NetworksSep 25 2017Recurrent neural networks (RNNs) are a vital modeling technique that rely on internal states learned indirectly by optimization of a supervised, unsupervised, or reinforcement training loss. RNNs are used to model dynamic processes that are characterized ... More
Rotational Rectification Network: Enabling Pedestrian Detection for Mobile VisionJun 19 2017Sep 12 2017Across a majority of pedestrian detection datasets, it is typically assumed that pedestrians will be standing upright with respect to the image coordinate system. This assumption, however, is not always valid for many vision-equipped mobile platforms ... More
Softer-NMS: Rethinking Bounding Box Regression for Accurate Object DetectionSep 23 2018Non-maximum suppression (NMS) is essential for state-of-the-art object detectors to localize object from a set of candidate locations. However, accurate candidate location sometimes is not associated with a high classification score, which leads to object ... More
The rate of growth of the minimum clique size of graphs of given order and chromatic numberOct 01 2012Feb 03 2014Let $Q(n,c)$ denote the minimum clique number over graphs with $n$ vertices and chromatic number $c$. We determine the rate of growth of of the sequence ${Q(n,\lceil rn \rceil)}_{n=1}^\infty$ for any fixed $0<r\leq 1$. We also give a better upper bound ... More
Mapping the Asymmetric Thick Disk: III. The Kinematics and Interaction with the Galactic BarDec 07 2010In the first two papers of this series, Larsen et al (2010a,b) describe our faint CCD survey in the inner Galaxy and map the over-density of Thick Disk stars in Quadrant I (Q1) to 5 kpc or more along the line of sight. The regions showing the strongest ... More
Visual Compiler: Synthesizing a Scene-Specific Pedestrian Detector and Pose EstimatorDec 15 2016We introduce the concept of a Visual Compiler that generates a scene specific pedestrian detector and pose estimator without any pedestrian observations. Given a single image and auxiliary scene information in the form of camera parameters and geometric ... More
Pattern Matching and Discourse Processing in Information Extraction from Japanese TextAug 01 1994Information extraction is the task of automatically picking up information of interest from an unconstrained text. Information of interest is usually extracted in two steps. First, sentence level processing locates relevant pieces of information scattered ... More
Fast UAV Trajectory Optimization using Bilevel Optimization with Analytical GradientsNov 27 2018This paper presents an efficient optimization framework that solves trajectory optimization problems efficiently by decoupling state variables from timing variables, thereby decomposing a challenging nonlinear programming (NLP) problem into two easier ... More
A Scalable Data Science Platform for Healthcare and Precision Medicine ResearchAug 14 2018Objective: To (1) demonstrate the implementation of a data science platform built on open-source technology within a large, academic healthcare system and (2) describe two computational healthcare applications built on such a platform. Materials and Methods: ... More
A Second Order Godunov Method for Multidimensional Relativistic MagnetohydrodynamicsJan 18 2011We describe a new Godunov algorithm for relativistic magnetohydrodynamics (RMHD) that combines a simple, unsplit second order accurate integrator with the constrained transport (CT) method for enforcing the solenoidal constraint on the magnetic field. ... More
Emergence of a 2d macro-spin liquid in a highly frustrated 3d quantum magnetFeb 18 2016The classical Ising model on the frustrated 3d swedenborgite lattice has disordered spin liquid ground states for all ratios of inter- and intra-planar couplings. Quantum fluctuations due to a transverse field give rise to several exotic quantum phenomena. ... More
The Spin-Resolved Atomic Velocity Distribution and 21-cm Line Profile of Dark-Age GasMay 02 2006The 21-cm hyperfine line of atomic hydrogen (HI) is a promising probe of the cosmic dark ages. In past treatments of 21-cm radiation it was assumed the hyperfine level populations of HI could be characterized by a velocity-independent ``spin temperature'' ... More
The Minimum Regularized Covariance Determinant estimatorJan 24 2017Dec 01 2018The Minimum Covariance Determinant (MCD) approach robustly estimates the location and scatter matrix using the subset of given size with lowest sample covariance determinant. Its main drawback is that it cannot be applied when the dimension exceeds the ... More
Pristine Dwarf-Galaxy Survey I: A detailed photometric and spectroscopic study of the very metal-poor Draco II satelliteJul 27 2018Aug 06 2018We present a detailed study of the faint Milky Way satellite Draco II (Dra II) from deep CFHT/MegaCam broadband $g$ and $i$ photometry and narrow-band metallicity-sensitive CaHK observations, along with follow-up Keck II/DEIMOS multi-object spectroscopy. ... More
The R-Process Alliance: Spectroscopic Follow-up of Low-Metallicity Star Candidates from the Best & Brightest SurveyNov 26 2018We present results from an observing campaign to identify low-metallicity stars in the Best & Brightest Survey. From medium-resolution (R ~ 1, 200 - 2, 000) spectroscopy of 857 candidates, we estimate the stellar atmospheric parameters (Teff, log g, and ... More
LBVs and Statistical InferenceAug 05 2016Smith and Tombleson (2015) asserted that statistical tests disprove the standard view of LBVs, and proposed a far more complex scenario to replace it. But Humphreys et al. (2016) showed that Smith and Tombleson's Magellanic "LBV" sample was a mixture ... More
Crossing the `Yellow Void' -- Spatially Resolved Spectroscopy of the Post- Red Supergiant IRC+10420 and Its Circumstellar EjectaMay 15 2002IRC +10420 is one of the extreme hypergiant stars that define the empirical upper luminosity boundary in the HR diagram. During their post--RSG evolution, these massive stars enter a temperature range (6000-9000 K) of increased dynamical instability, ... More
LBVs and Statistical InferenceAug 05 2016Nov 27 2016Smith and Tombleson (2015) asserted that statistical tests disprove the standard view of LBVs, and proposed a far more complex scenario to replace it. But Humphreys et al. (2016) showed that Smith and Tombleson's Magellanic "LBV" sample was a mixture ... More
The Effects of Rayleigh Scattering on the CMB and Cosmic StructureOct 23 2014During and after recombination, in addition to Thomson scattering with free electrons, photons also coupled to neutral hydrogen and helium atoms through Rayleigh scattering. This coupling influences both CMB anisotropies and the distribution of matter ... More
Recovery from Giant Eruptions in Very Massive StarsOct 21 2015Dec 09 2015We use a hydro-and-radiative-transfer code to explore the behavior of a very massive star (VMS) after a giant eruption -- i.e., following a supernova impostor event. Beginning with reasonable models for evolved VMSs with masses of $80~M_\odot$ and $120~M_\odot$, ... More
The Early Spectra of Eta Carinae 1892 to 1941 and the Onset of Its High Excitation Emission SpectrumJan 18 2008The observed behavior of eta Car from 1860 to 1940 has not been considered in most recent accounts, nor has it been explained in any quantitative model. We have used modern digital processing techniques to examine Harvard objective-prism spectra made ... More
The Ring of Integers in the Canonical Structures of the PlanesJul 05 2007The \emph{canonical structures of the plane} are those that result, up to isomorphism, from the rings that have the form $\mathds{R}[x]/(ax^2+bx+c)$ with $a\neq 0$.That ring is isomorphic to $\mathds{R}[\theta]$, where $\theta$ is the equivalence class ... More
How to apply multiple imputation in propensity score matching with partially observed confounders: a simulation study and practical recommendationsApr 16 2019Propensity score matching (PSM) has been widely used to mitigate confounding in observational studies, although complications arise when the covariates used to estimate the PS are only partially observed. Multiple imputation (MI) is a potential solution ... More
An R- and I-Band Photometric Variability Survey of the Cygnus OB2 AssociationSep 28 2010We present a catalog of photometrically variable stars discovered within two 21'.3 X 21'.3 fields centered on the Cygnus OB2 association. There have hitherto been no deep optical variability studies of Cyg OB2 despite it being replete with early-type ... More
Community structure detection and evaluation during the pre- and post-ictal hippocampal depth recordingsMar 14 2018May 31 2018Detecting and evaluating regions of brain under various circumstances is one of the most interesting topics in computational neuroscience. However, the majority of the studies on detecting communities of a functional connectivity network of the brain ... More
Engineering Local optimality in Quantum Monte Carlo algorithmsAug 19 2005Jul 28 2007Quantum Monte Carlo algorithms based on a world-line representation such as the worm algorithm and the directed loop algorithm are among the most powerful numerical techniques for the simulation of non-frustrated spin models and of bosonic models. Both ... More
The Chrysalis Opens? Photometry from the Eta Carinae HST Treasury Project, 2002-2006Sep 11 2006During the past decade Eta Car has brightened markedly, possibly indicating a change of state. Here we summarize photometry gathered by the Hubble Space Telescope as part of the HST Treasury Project on this object. Our data include STIS/CCD acquisition ... More
Quantum Monte Carlo Simulation of the High-Pressure Molecular-Atomic Crossover in Fluid HydrogenMar 28 2006Dec 09 2006A first-order liquid-liquid phase transition in high-pressure hydrogen between molecular and atomic fluid phases has been predicted in computer simulations using ab initio molecular dynamics approaches. However, experiments indicate that molecular dissociation ... More
A High-Resolution Study of Eta Carinae's Outer EjectaJul 25 2002Eta Carinae is a very luminous and unstable evolved star. Outflowing material ejected during the star's giant eruption in 1843 surrounds it as a nebula which consists of an inner bipolar region(the Homunculus) and the Outer Ejecta. The outer ejecta is ... More
On the Social Traits of Luminous Blue VariablesMar 03 2016Apr 21 2016In a recent paper, Smith and Tombleson (2015) state that the Luminous Blue Variables (LBVs) in the Milky Way and the Magellanic Clouds are isolated; that they are not spatially associated with young O-type stars. They propose a novel explanation that ... More
High Resolution, Long - Slit Spectroscopy of VY CMa: The Evidence for Localized High Mass Loss EventsOct 16 2004High spatial and spectral resolution spectroscopy of the OH/IR supergiant VY CMa and its circumstellar ejecta reveals evidence for high mass loss events from localized regions on the star occurring over the past 1000 years. The reflected absorption lines ... More
Local Simulations of Instabilities in Relativistic Jets I: Morphology and Energetics of the Current-Driven InstabilityJan 12 2012Feb 20 2012We present the results of a numerical investigation of current-driven instability in magnetized jets. Utilizing the well-tested, relativistic magnetohydrodynamic code Athena, we construct an ensemble of local, co-moving plasma columns in which initial ... More
The Morphology of IRC +10420's Circumstellar EjectaJun 02 2010Images of the circumstellar ejecta associated with the post-red supergiant IRC +10420 show a complex ejecta with visual evidence for episodic mass loss. In this paper we describe the transverse motions of numerous knots, arcs and condensations in the ... More
Topological Analysis of High-Resolution CMB MapsMar 27 1998Mar 30 1998We report the development of numerical tools for the topological analysis of sub--degree resolution, all--sky maps. Software to be released in the HEALFAST (V0.9) package defines neighbour relationships for the HEALPIX tessellation of the sphere. We apply ... More
Mid-Cycle Changes in Eta CarinaeAug 12 2009Apr 26 2010In late 2006, ground-based photometry of $\eta$ Car plus the Homunculus showed an unexpected decrease in its integrated apparent brightness, an apparent reversal of its long-term brightening. Subsequent HST/WFPC2 photometry of the central star in the ... More
Optical Design of PICO, a Concept for a Space Mission to Probe Inflation and Cosmic OriginsAug 03 2018The Probe of Inflation and Cosmic Origins (PICO) is a probe-class mission concept currently under study by NASA. PICO will probe the physics of the Big Bang and the energy scale of inflation, constrain the sum of neutrino masses, measure the growth of ... More
Experimental Clock Calibration\\on a Crystal-Free Mote-on-a-ChipApr 17 2019The elimination of the off-chip frequency reference, typically a crystal oscillator, would bring important benefits in terms of size, price and energy efficiency to IEEE802.15.4 compliant radios and systems-on-chip. The stability of on-chip oscillators ... More
A finite element approach to self-consistent field theory calculations of multiblock polymersJul 11 2016Self-consistent field theory (SCFT) has proven to be a powerful tool for modeling equilibrium microstructures of soft materials, particularly for multiblock polymers. A very successful approach to numerically solving the SCFT set of equations is based ... More
High-excitation emission lines near eta Carinae, and its likely companion starDec 06 2009In order to study the distribution of gas and ionizing radiation around eta Car and their implications for its likely companion star, we have examined high-excitation emission lines of [Ne III], [Fe III], etc., in spectra obtained with the HST/STIS instrument ... More
Learning the Problem-Optimum Map: Analysis and Application to Global Optimization in RoboticsMay 16 2016This paper describes a data-driven framework for approximate global optimization in which precomputed solutions to a sample of problems are retrieved and adapted during online use to solve novel problems. This approach has promise for real-time applications ... More
Giant eruptions of very massive starsFeb 11 2016Giant eruptions or supernova-impostor events are far more mysterious than true supernovae. An extreme example can release as much radiative energy as a SN, ejecting several M_sun of material. These events involve continuous radiation-driven outflows rather ... More
Finite automata and relations of multiple zeta valuesMar 26 2004The theory of finite automata applies to the study on relations of multiple zeta values.
QMCPACK : An open source ab initio Quantum Monte Carlo package for the electronic structure of atoms, molecules, and solidsFeb 20 2018Apr 04 2018QMCPACK is an open source quantum Monte Carlo package for ab-initio electronic structure calculations. It supports calculations of metallic and insulating solids, molecules, atoms, and some model Hamiltonians. Implemented real space quantum Monte Carlo ... More
Approximation of holomorphic mappings on 1-convex domainsMay 18 2013Nov 12 2013Let \pi :Z\to X be a holomorphic submersion of a complex manifold Z onto a complex manifold X and D\Subset X a 1-convex domain with strongly pseudoconvex boundary. We prove that under certain conditions there always exists a spray of \pi -sections over ... More
Testing Emergent Gravity with Isolated Dwarf GalaxiesJun 02 2017Verlinde (2016) has proposed a new modified theory of gravity, Emergent Gravity (EG), as an alternative to dark matter. EG reproduces the Tully-Fisher relationship with no free parameters, and agrees with the velocity curves of most massive, spiral galaxies ... More
Electrical conductivity of high-pressure liquid hydrogen by quantum Monte Carlo methodsSep 11 2009Jan 22 2010We compute the electrical conductivity for liquid hydrogen at high pressure using quantum Monte Carlo. The method uses Coupled Electron-Ion Monte Carlo to generate configurations of liquid hydrogen. For each configuration correlated sampling of electrons ... More
Trial wave functions for High-Pressure Metallic HydrogenDec 03 2007Many body trial wave functions are the key ingredient for accurate Quantum Monte Carlo estimates of total electronic energies in many electron systems. In the Coupled Electron-Ion Monte Carlo method, the accuracy of the trial function must be conjugated ... More
Turbulence In the Outer Regions of Protoplanetary Disks. II. Strong Accretion Driven by a Vertical Magnetic FieldJun 13 2013Aug 12 2013We carry out a series of local, vertically stratified shearing box simulations of protoplanetary disks that include ambipolar diffusion and a net vertical magnetic field. The ambipolar diffusion profiles we employ correspond to 30AU and 100AU in a minimum ... More
Chemical Abundances of Luminous Cool Stars in the Galactic Center from High-Resolution Infrared SpectroscopyJul 18 2007We present chemical abundances in a sample of luminous cool stars located within 30 pc of the Galactic Center. Abundances of carbon, nitrogen, oxygen, calcium, and iron were derived from high-resolution infrared spectra in the H- and K-bands. The abundance ... More
A spectroscopic event of eta Car viewed from different directions: The data and first resultsJan 28 2005We present spectroscopic observations with high spectral resolution of eta Car as seen by the SE lobe of the Homunculus nebula over the 2003.5 "spectroscopic event". The observed spectra represent the stellar spectrum emitted near the pole of the star ... More
VLT-UVES observations of the Balmer line variations of eta Carinae during the 2003 spectroscopic eventDec 17 2004We present high spectral resolution echelle observations of the Balmer line variations during the 2003.5 ``spectroscopic event'' of eta Carinae. Spectra have been recorded of both eta Carinae and the Homunculus at the FOS4 position in its SE lobe. This ... More
Critical Differences and Clues in Eta Car's 2009 EventJun 29 2011We monitored Eta Carinae with HST WFPC2 and Gemini GMOS throughout the 2009 spectroscopic event, which was expected to differ from its predecessor in 2003 (Davidson et al. 2005). Here we report major observed differences between events, and their implications. ... More
Penetrating the Homunculus -- Near-Infrared Adaptive Optics Images of Eta CarinaeMar 24 2011Near-infrared adaptive optics imaging with NICI and NaCO reveal what appears to be a three-winged or lobed pattern, the "butterfly nebula", outlined by bright Br$\gamma$ and H$_{2}$ emission and light scattered by dust. In contrast, the [Fe II] emission ... More
Phase diagram of Bose-Fermi mixtures in one-dimensional optical latticesDec 12 2005May 23 2006The ground state phase diagram of the one-dimensional Bose-Fermi Hubbard model is studied in the canonical ensemble using a quantum Monte Carlo method. We focus on the case where both species have half filling in order to maximize the pairing correlations ... More
Quantifying energetics and dissipation in magnetohydrodynamic turbulenceMar 20 2013Nov 25 2013We perform a suite of two- and three-dimensional magnetohydrodynamic (MHD) simulations with the Athena code of the non-driven Kelvin-Helmholtz instability in the subsonic, weak magnetic field limit. Focusing the analysis on the non-linear turbulent regime, ... More
Strong coupling of Jahn-Teller distortion to oxygen-octahedron rotation and functional properties in epitaxially-strained orthorhombic LaMnO$_3$Jul 12 2013First-principles calculations reveal a large cooperative coupling of Jahn-Teller (JT) distortion to oxygen-octahedron rotations in perovskite LaMnO$_3$. The combination of the two distortions is responsible for stabilizing the strongly orthorhombic $A$-AFM ... More
Turbulence In the Outer Regions of Protoplanetary Disks. I. Weak Accretion with No Vertical Magnetic FluxOct 15 2012Jan 15 2013We use local numerical simulations to investigate the strength and nature of magnetohydrodynamic (MHD) turbulence in the outer regions of protoplanetary disks, where ambipolar diffusion is the dominant non-ideal MHD effect. The simulations include vertical ... More
Near-infrared counterparts of Chandra X-ray sources toward the Galactic CenterJul 20 2010The Chandra X-ray Observatory has now discovered nearly 10,000 X-ray point sources in the 2 x 0.8 degree region around the Galactic Center (Muno 2009). The sources are likely to be a population of accreting binaries in the Galactic Center, but little ... More
Global Simulations of Accretion Disks I: Convergence and Comparisons with Local ModelsJun 20 2011Grid-based magnetohydrodynamic (MHD) simulations have proven invaluable for the study of astrophysical accretion disks. However, the fact that angular momentum transport in disks is mediated by MHD turbulence (with structure down to very small scales) ... More
Luminous and Variable Stars in M31 and M33. I. The Warm Hypergiants and Post-Red Supergiant EvolutionMay 26 2013The progenitors of Type IIP supernovae have an apparent upper limit to their initial masses of about 20 solar masses, suggesting that the most massive red supergiants evolve to warmer temperatures before their terminal explosion. But very few post-red ... More
Luminous and Variable Stars in M31 and M33. II. Luminous Blue Variables, Candidate LBVs, Fe II Emission Line Stars, and Other SupergiantsJul 08 2014An increasing number of non-terminal eruptions are being found in the numerous surveys for optical transients. Very little is known about these giant eruptions, their progenitors and their evolutionary state. A greatly improved census of the likely progenitor ... More
Long-range strain correlations in 3D quiescent glass forming liquidsJun 30 2018We present a quantitative study of strain correlations in quiescent supercooled liquids and glasses. Recent two-dimensional computer simulations and experiments indicate that even supercooled liquids exhibit long-lived, long-range strain correlations. ... More
The Canada-UK Deep Submillimetre Survey VIII: Source Identifications in the 3-hour fieldDec 10 2003We present optical, near-infrared and radio observations of the 3-hour field of the Canada-UK Deep Submillimetre Survey. Of the 27 submillimetre sources in the field, nine have secure identifications with either a radio source or a near-IR source. We ... More
Units of $\mathbb{Z}C_{p^n}$Jul 19 2013Jul 22 2013Let $p$ be a prime integer and $n,i$ be positive integers such that \linebreak $S=\{-1, \ \theta, \ \mu_i=1+\theta+... + \theta^{i-1} \ \mid 1 < i < \frac{p^n}{2}, \ gcd(p^n,i)=1 \}$ generates the group of units of $\mathbb{Z}[\theta],$ where $\theta$ ... More
Secular Changes in Eta Carinae's Wind 1998-2011Dec 19 2011Feb 24 2012Stellar wind-emission features in the spectrum of eta Carinae have decreased by factors of 1.5-3 relative to the continuum within the last 10 years. We investigate a large data set from several instruments (STIS, GMOS, UVES) obtained between 1998 and ... More