Results for "Noah J. Planavsky"

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The remote detectability of Earth's biosphere through time and the importance of UV capability for characterizing habitable exoplanetsMar 13 2019Thousands of planets beyond our solar system have been discovered to date, dozens of which are rocky in composition and are orbiting within the circumstellar habitable zone of their host star. The next frontier in life detection beyond our solar system ... More
The Super-Earth Opportunity - Search for Habitable Exoplanets in the 2020sMar 12 2019The recent discovery of a staggering diversity of planets beyond the Solar System has brought with it a greatly expanded search space for habitable worlds. The Kepler exoplanet survey has revealed that most planets in our interstellar neighborhood are ... More
Generalizations of a Curious Family of MSTD Sets Hidden By Interior BlocksAug 16 2018A set $A$ is MSTD (more-sum-than-difference) or sum-dominant if $|A+A|>|A-A|$ and is RSD (restricted-sum dominant) if $|A\hat{+}A|>|A-A|$, where $A\hat{+}A$ is the sumset of $A$ without a number added to itself. We study an interesting family of MSTD ... More
Quantum mechanical evolution towards thermal equilibriumDec 12 2008The circumstances under which a system reaches thermal equilibrium, and how to derive this from basic dynamical laws, has been a major question from the very beginning of thermodynamics and statistical mechanics. Despite considerable progress, it remains ... More
Mass-structure of weighted real treesJan 08 2018Rooted, weighted continuum random trees are used to describe limits of sequences of random discrete trees. Formally, they are random quadruples $(\mathcal{T},d,r,p)$, where $(\mathcal{T},d)$ is a tree-like metric space, $r\in\mathcal{T}$ is a distinguished ... More
The Liouville phenomenon in the deformation problem of coisotropicsMay 16 2008The work of Oh and Park ([OP]) on the deformation problem of coisotropic submanifolds opened the possibility of studying a large and interesting class of foliations with some explicit geometric tools. These tools assemble into the structure of an L-infinity ... More
The largest $(k, \ell)$-sum-free sets in compact abelian groupsJan 10 2019Jan 15 2019A subset $A$ of a finite abelian group is called $(k,\ell)$-sum-free if $kA \cap \ell A=\emptyset.$ In this paper, we extend this concept to compact abelian groups and study the question of how large a measurable $(k,\ell)$-sum-free set can be. For integers ... More
Generating Giant Spin Currents Using Nodal Topological SuperconductorsOct 12 2015Oct 22 2015In this work, we show that a giant spin current can be injected into a nodal topological superconductor, using a normal paramagnetic lead, through a large number of zero energy Majorana fermions at the superconductor edge. The giant spin current is caused ... More
Equilibration time scales of physically relevant observablesSep 18 2015Aug 28 2017We address the problem of understanding from first principles the conditions under which a quantum system equilibrates rapidly with respect to a concrete observable. On the one hand previously known general upper bounds on the time scales of equilibration ... More
Chern numbers hiding in time-of-flight imagesMay 16 2011Jan 06 2012We present a technique for detecting topological invariants -- Chern numbers -- from time-of-flight images of ultra-cold atoms. We show that the Chern numbers of integer quantum Hall states of lattice fermions leave their fingerprints in the atoms' momentum ... More
Radiatively induced symmetry breaking and the conformally coupled magnetic monopole in AdS spaceOct 29 2013We implement quantum corrections for a magnetic monopole in a classically conformally invariant theory containing gravity. This yields the trace (conformal) anomaly and introduces a length scale in a natural fashion via the process of renormalization. ... More
Projective linear configurations via non-reductive actionsJan 03 2014We study the iterated blow-up X of projective space along an arbitrary collection of linear subspaces. By replacing the universal torsor with an $\mathbb{A}^1$-homotopy equivalent model, built from $\mathbb{A}^1$-fiber bundles not just algebraic line ... More
The cone of type A, level one conformal blocks divisorsMay 16 2011May 17 2011We prove that the type A, level one, conformal blocks divisors on $\bar{M}_{0,n}$ span a finitely generated, full-dimensional subcone of the nef cone. Each such divisor induces a morphism from $\bar{M}_{0,n}$, and we identify its image as a GIT quotient ... More
A time-distance trade-off for GDD with preprocessing---Instantiating the DLW heuristicFeb 22 2019Feb 25 2019For $0 \leq \alpha \leq 1/2$, we show an algorithm that does the following. Given appropriate preprocessing $P(\mathcal{L})$ consisting of $N_\alpha := 2^{O(n^{1-2\alpha} + \log n)}$ vectors in some lattice $\mathcal{L} \subset \mathbb{R}^n$ and a target ... More
A new inequality for the von Neumann entropyJun 22 2004Strong subadditivity of von Neumann entropy, proved in 1973 by Lieb and Ruskai, is a cornerstone of quantum coding theory. All other known inequalities for entropies of quantum systems may be derived from it. Here we prove a new inequality for the von ... More
Modular interpretation of a non-reductive Chow quotientSep 11 2015Sep 17 2017The space of n distinct points and a disjoint parameterized hyperplane in projective d-space up to projectivity---equivalently, configurations of n distinct points in affine d-space up to translation and homothety---has a beautiful compactification introduced ... More
Principal component analysis of IUE galaxy spectraFeb 12 2004We analyse the UV spectral energy distribution of a sample of normal galaxies listed in the IUE-INES Guide No. 2-Normal Galaxies (Formiggini & Brosch, 2000) using a Principal Component Analysis. The sample consists of the IUE-SW spectra of the central ... More
Path Intergals and Perturbative Expansions for Non-Compact Symmetric SpacesFeb 05 1992We show how to construct path integrals for quantum mechanical systems where the space of configurations is a general non-compact symmetric space. Associated with this path integral is a perturbation theory which respects the global structure of the system. ... More
On the local pairing behavior of critical points and roots of random polynomialsOct 16 2018Feb 05 2019We study the pairing between zeros and critical points of the polynomial $p_n(z) = \prod_{j=1}^n(z-X_j)$, whose roots $X_1, \ldots, X_n$ are complex-valued random variables. Under a regularity assumption, we show that if the roots are independent and ... More
Pairing between zeros and critical points of random polynomials with independent rootsOct 19 2016Jul 28 2017Let $p_n$ be a random, degree $n$ polynomial whose roots are chosen independently according to the probability measure $\mu$ on the complex plane. For a deterministic point $\xi$ lying outside the support of $\mu$, we show that almost surely the polynomial ... More
The Arecibo Legacy Fast ALFA Survey: VI. Second HI Source Catalog of the Virgo Cluster RegionJun 19 2008We present the third installment of HI sources extracted from the Arecibo Legacy Fast ALFA extragalactic survey. This dataset continues the work of the Virgo ALFALFA catalog. The catalogs and spectra published here consist of data obtained during the ... More
"You are no Jack Kennedy": On Media Selection of Highlights from Presidential DebatesFeb 23 2018Political speeches and debates play an important role in shaping the images of politicians, and the public often relies on media outlets to select bits of political communication from a large pool of utterances. It is an important research question to ... More
Friendships, Rivalries, and Trysts: Characterizing Relations between Ideas in TextsApr 25 2017Jul 16 2017Understanding how ideas relate to each other is a fundamental question in many domains, ranging from intellectual history to public communication. Because ideas are naturally embedded in texts, we propose the first framework to systematically characterize ... More
Impacts of Quantum Chemistry Calculations on Exoplanetary Science, Planetary Astronomy, and AstrophysicsApr 15 2019Several of NASA missions (TESS, JWST, WFIRST, etc.) and mission concepts (LUVOIR, HabEx, and OST) emphasize the exploration and characterization of exoplanets, and the study of the interstellar medium. We anticipate that a much broader set of chemical ... More
GIT Compactifications of M_{0,n} and FlipsDec 01 2011Feb 05 2016We use geometric invariant theory (GIT) to construct a large class of compactifications of the moduli space M_{0,n}. These compactifications include many previously known examples, as well as many new ones. As a consequence of our GIT approach, we exhibit ... More
A Developer-Friendly Library for Smart Home IoT Privacy-Preserving Traffic ObfuscationAug 22 2018The number and variety of Internet-connected devices have grown enormously in the past few years, presenting new challenges to security and privacy. Research has shown that network adversaries can use traffic rate metadata from consumer IoT devices to ... More
Closing the Blinds: Four Strategies for Protecting Smart Home Privacy from Network ObserversMay 18 2017The growing market for smart home IoT devices promises new conveniences for consumers while presenting novel challenges for preserving privacy within the home. Specifically, Internet service providers or neighborhood WiFi eavesdroppers can measure Internet ... More
Identifiability and testability in GRT with Individual DifferencesJun 17 2016Jul 29 2016Silbert and Thomas (2013) showed that failures of decisional separability are not, in general, identifiable in fully parameterized $2 \times 2$ Gaussian GRT models. A recent extension of $2 \times 2$ GRT models (GRTwIND) was developed to solve this problem ... More
NMR Quantum Logic Gates for Homonuclear Spin SystemsJul 01 1999If NMR systems are to be used as practical quantum computers, the number of coupled spins will need to be so large that it is not feasible to rely on purely heteronuclear spin systems. The implementation of a quantum logic gate imposes certain constraints ... More
Synchronization Behavior in a Novel Phase ModelMar 24 2019Localized traveling-wave solutions to a nonlinear Schrodinger equation were recently shown to be a consequence of Fourier mode synchronization. The reduced dynamics describing mode interaction take the form of a phase model with novel ternary coupling. ... More
A Blockwise Descent Algorithm for Group-penalized Multiresponse and Multinomial RegressionNov 26 2013In this paper we purpose a blockwise descent algorithm for group-penalized multiresponse regression. Using a quasi-newton framework we extend this to group-penalized multinomial regression. We give a publicly available implementation for these in R, and ... More
Layer-structured 3D Scene Inference via View SynthesisJul 26 2018We present an approach to infer a layer-structured 3D representation of a scene from a single input image. This allows us to infer not only the depth of the visible pixels, but also to capture the texture and depth for content in the scene that is not ... More
Spatially Extended Tests of a Neural Network Parametrization Trained by Coarse-grainingApr 06 2019General circulation models (GCMs) typically have a grid size of 25--200 km. Parametrizations are used to represent diabatic processes such as radiative transfer and cloud microphysics and account for sub-grid-scale motions and variability. Unlike traditional ... More
Redesigning a junior-level electronics course to support engagement in scientific practicesJul 14 2015Building on successful work on studying and transforming our senior-level Advanced Lab course, we have transformed our junior-level Electronics course to engage students in a variety of authentic scientific practices, including constructing, testing, ... More
Optimal Control with Noisy TimeDec 31 2013This paper examines stochastic optimal control problems in which the state is perfectly known, but the controller's measure of time is a stochastic process derived from a strictly increasing L\'evy process. We provide dynamic programming results for continuous-time ... More
The Propagation of Quantum Information Through a Spin SystemDec 16 2003It has been recently suggested that the dynamics of a quantum spin system may provide a natural mechanism for transporting quantum information. We show that one dimensional rings of qubits with fixed (time-independent) interactions, constant around the ... More
Unsupervised Learning of Depth and Ego-Motion from VideoApr 25 2017Aug 01 2017We present an unsupervised learning framework for the task of monocular depth and camera motion estimation from unstructured video sequences. We achieve this by simultaneously training depth and camera pose estimation networks using the task of view synthesis ... More
Aldous diffusion I: a projective system of continuum $k$-tree evolutionsSep 20 2018The Aldous diffusion is a conjectured Markov process on the space of real trees that is the continuum analogue of discrete Markov chains on binary trees. We construct this conjectured process via a consistent system of stationary evolutions of binary ... More
Uniform control of local times of spectrally positive stable processesSep 21 2016We establish two results about local times of spectrally positive stable processes. The first is a general approximation result, uniform in space and on compact time intervals, in a model where each jump of the stable process may be marked by a random ... More
Evidence for frequency-dependent extracellular impedance from the transfer function between extracellular and intracellular potentialsAug 22 2009May 17 2010We examine the properties of the transfer function F_T = V_m / V_{LFP} between the intracellular membrane potential (V_m) and the local field potential (V_{LFP}) in cerebral cortex. We first show theoretically that, in the subthreshold regime, the frequency ... More
Chorus: Differential Privacy via Query RewritingSep 20 2018Sep 23 2018We present Chorus, a system with a novel architecture for providing differential privacy for statistical SQL queries. The key to our approach is to embed a differential privacy mechanism into the query before execution so the query automatically enforces ... More
The Quantum Entropy Cone of Stabiliser StatesFeb 21 2013Jul 02 2013We investigate the universal linear inequalities that hold for the von Neumann entropies in a multi-party system, prepared in a stabiliser state. We demonstrate here that entropy vectors for stabiliser states satisfy, in addition to the classic inequalities, ... More
Applying Probabilistic Programming to Affective ComputingMar 15 2019Affective Computing is a rapidly growing field spurred by advancements in artificial intelligence, but often, held back by the inability to translate psychological theories of emotion into tractable computational models. To address this, we propose a ... More
Greedy, Joint Syntactic-Semantic Parsing with Stack LSTMsJun 29 2016We present a transition-based parser that jointly produces syntactic and semantic dependencies. It learns a representation of the entire algorithm state, using stack long short-term memories. Our greedy inference algorithm has linear time, including feature ... More
Pinning and Depinning: from periodic to chaotic and random mediaSep 12 2018We study propagation of dissipative structures in inhomogeneous media with a focus on pinning and depinning transitions. We model spatial complexity in the medium as generated by dynamical systems. We are thus able to capture transitions from periodic ... More
Inoculation by Fine-Tuning: A Method for Analyzing Challenge DatasetsApr 04 2019Several datasets have recently been constructed to expose brittleness in models trained on existing benchmarks. While model performance on these challenge datasets is significantly lower compared to the original benchmark, it is unclear what particular ... More
Diffusions on a space of interval partitions with Poisson-Dirichlet stationary distributionsSep 21 2016Mar 21 2017We construct a pair of related diffusions on a space of interval partitions of the unit interval $[0,1]$ that are stationary with the Poisson-Dirichlet laws with parameters (1/2,0) and (1/2,1/2) respectively. These are two particular cases of a general ... More
Decoupling edge versus bulk conductance in the trivial regime of an InAs/GaSb double quantum well using Corbino ring geometryMay 16 2016A Corbino ring geometry is utilized to analyze edge and bulk conductance of InAs/GaSb quantum well structures. We show that edge conductance exists in the trivial regime of this theoretically-predicted topological system with a temperature insensitive ... More
Sustaining Educational Reforms in Introductory PhysicsMay 02 2008While it is well known which curricular practices can improve student performance on measures of conceptual understanding, the sustaining of these practices and the role of faculty members in implementing these practices are less well understood. We present ... More
Quantum speedup of the Travelling Salesman Problem for bounded-degree graphsDec 19 2016The Travelling Salesman Problem is one of the most famous problems in graph theory. However, little is currently known about the extent to which quantum computers could speed up algorithms for the problem. In this paper, we prove a quadratic quantum speedup ... More
Studying Expert Practices to Create Learning Goals for Electronics LabsJul 11 2014Laboratory courses for upper-division undergraduates often involve sophisticated equipment, relatively small class sizes, and extended hands-on projects. These courses present distinct challenges and opportunities for the physics education research community ... More
Keeping the Smart Home Private with Smart(er) IoT Traffic ShapingDec 03 2018The proliferation of smart home Internet of Things (IoT) devices presents unprecedented challenges for preserving privacy within the home. In this paper, we demonstrate that a passive network observer (e.g., an Internet service provider) can infer private ... More
Deep Feature Interpolation for Image Content ChangesNov 16 2016Jun 19 2017We propose Deep Feature Interpolation (DFI), a new data-driven baseline for automatic high-resolution image transformation. As the name suggests, it relies only on simple linear interpolation of deep convolutional features from pre-trained convnets. We ... More
Closed sets of non-local correlationsAug 11 2009Oct 15 2009We introduce a fundamental concept -- closed sets of correlations -- for studying non-local correlations. We argue that sets of correlations corresponding to information-theoretic principles, or more generally to consistent physical theories, must be ... More
Annotation Artifacts in Natural Language Inference DataMar 06 2018Apr 16 2018Large-scale datasets for natural language inference are created by presenting crowd workers with a sentence (premise), and asking them to generate three new sentences (hypotheses) that it entails, contradicts, or is logically neutral with respect to. ... More
Joint Mapping and Calibration via Differentiable Sensor FusionNov 21 2018Dec 20 2018We leverage automatic differentiation (AD) and probabilistic programming to develop an end-to-end optimization algorithm for batch triangulation of a large number of unknown objects. Given noisy detections extracted from noisily geo-located street level ... More
Probing Majorana Flat Bands in Nodal $d_{x^2-y^2}$-wave Superconductors with Rashba Spin-Orbit CouplingMay 28 2013We show that Majorana fermions associated with Majorana flat bands emerge as zero energy modes on the [110] edge of single layer or multilayer nodal superconductors with $d_{x^2-y^2}$-wave pairing and Rashba spin-orbit coupling. Moreover, as long as the ... More
Nonlinear manifestations of photon acceleration in time-dependent metasurfaces: tunable broadband harmonics generationOct 19 2017Jan 13 2019Time-dependent nonlinear media, such as rapidly generated plasmas produced via laser ionization of gases, can increase the energy of individual laser photons and generate tunable high-order harmonic pulses. This phenomenon, known as photon acceleration, ... More
Estimation of cell lineage trees by maximum-likelihood phylogeneticsMar 29 2019CRISPR technology has enabled large-scale cell lineage tracing for complex multicellular organisms by mutating synthetic genomic barcodes during organismal development. However, these sophisticated biological tools currently use ad-hoc and outmoded computational ... More
Casimir Force at a Knife's EdgeOct 24 2009Jul 06 2010The Casimir force has been computed exactly for only a few simple geometries, such as infinite plates, cylinders, and spheres. We show that a parabolic cylinder, for which analytic solutions to the Helmholtz equation are available, is another case where ... More
Electromagnetic Casimir Forces of Parabolic Cylinder and Knife-Edge GeometriesMar 30 2011An exact calculation of electromagnetic scattering from a perfectly conducting parabolic cylinder is employed to compute Casimir forces in several configurations. These include interactions between a parabolic cylinder and a plane, two parabolic cylinders, ... More
Ising Superconductivity and Majorana Fermions in Transition Metal DichalcogenidesOct 21 2015Apr 12 2016In monolayer transition metal dichalcogenides (TMDs), electrons in opposite $K$ valleys are subject to opposite effective Zeeman fields, which are referred to as Ising spin-orbit coupling (SOC) fields. The Ising SOC, originated from in-plane mirror symmetry ... More
An extremal problem on crossing vectorsMay 08 2012Aug 19 2014For positive integers $w$ and $k$, two vectors $A$ and $B$ from $\mathbb{Z}^w$ are called $k$-crossing if there are two coordinates $i$ and $j$ such that $A[i]-B[i]\geq k$ and $B[j]-A[j]\geq k$. What is the maximum size of a family of pairwise $1$-crossing ... More
Pushing the Boundaries of View Extrapolation with Multiplane ImagesMay 01 2019We explore the problem of view synthesis from a narrow baseline pair of images, and focus on generating high-quality view extrapolations with plausible disocclusions. Our method builds upon prior work in predicting a multiplane image (MPI), which represents ... More
A Framework for Transforming Departmental Culture to Support Educational InnovationDec 09 2014Aug 29 2015This paper provides a research-based framework for promoting institutional change in higher education. To date, most educational change efforts have focused on relatively narrow subsets of the university system (e.g., faculty teaching practices or administrative ... More
Amorphous topological insulators constructed from random point setsDec 29 2016Oct 09 2018The discovery that the band structure of electronic insulators may be topologically non-trivial has unveiled distinct phases of electronic matter with novel properties. Recently, mechanical lattices have been found to have similarly rich structure in ... More
Dynamic Social Balance and Convergent Appraisals via Homophily and Influence MechanismsOct 26 2017Feb 05 2019Social balance theory describes allowable and forbidden configurations of the topologies of signed directed social appraisal networks. In this paper, we propose two discrete-time dynamical systems that explain how an appraisal network \textcolor{blue}{converges ... More
Polar Ring Galaxies in the Galaxy ZooFeb 22 2012Mar 08 2012We report observations of 16 candidate polar ring galaxies (PRGs) identified by the Galaxy Zoo project in the Sloan Digital Sky Survey (SDSS) database. Deep images of five galaxies are available in the SDSS Stripe82 database, while to reach similar depth ... More
On the speed of fluctuations around thermodynamic equilibriumJul 07 2009We study the speed of fluctuation of a quantum system around its thermodynamic equilibrium state, and show that the speed will be extremely small for almost all times in typical thermodynamic cases. The setting considered here is that of a quantum system ... More
Continual Prediction from EHR Data for Inpatient Acute Kidney InjuryFeb 26 2019Acute kidney injury (AKI) commonly occurs in hospitalized patients and can lead to serious medical complications. In order to optimally predict AKI before it develops at any time during a hospital stay, we present a novel framework in which AKI is continually ... More
Model-Based Reasoning in the Upper-Division Physics Laboratory: Framework and Initial ResultsOct 03 2014Feb 23 2015We review and extend existing frameworks on modeling to develop a new framework that describes model-based reasoning in upper-division physics labs. Constructing and using models are core scientific practices that have gained significant attention within ... More
No quantum advantage for nonlocal computationOct 12 2006We investigate the problem of "nonlocal" computation, in which separated parties must compute a function with nonlocally encoded inputs and output, such that each party individually learns nothing, yet together they compute the correct function output. ... More
Products of Weighted Logic ProgramsJun 15 2010Weighted logic programming, a generalization of bottom-up logic programming, is a well-suited framework for specifying dynamic programming algorithms. In this setting, proofs correspond to the algorithm's output space, such as a path through a graph or ... More
Rapid spatial equilibration of a particle in a boxJun 11 2015Jun 29 2015We study the equilibration behaviour of a quantum particle in a one-dimensional box, with respect to a coarse grained position measurement (whether it lies in a certain spatial window or not). We show that equilibration in this context indeed takes place ... More
Infinite Families of Partitions into MSTD SubsetsAug 16 2018A set $A$ is MSTD (more-sum-than-difference) if $|A+A|>|A-A|$. Though MSTD sets are rare, Martin and O'Bryant proved that there exists a positive constant lower bound for the proportion of MSTD subsets of $\{1,2,\ldots ,r\}$ as $r\rightarrow\infty$. Asada ... More
An epistemology and expectations survey about experimental physics: Development and initial resultsOct 03 2013May 02 2014In response to national calls to better align physics laboratory courses with the way physicists engage in research, we have developed an epistemology and expectations survey to assess how students perceive the nature of physics experiments in the contexts ... More
Incorporating learning goals about modeling into an upper-division physics laboratory experimentJan 18 2013Nov 14 2013Implementing a laboratory activity involves a complex interplay among learning goals, available resources, feedback about the existing course, best practices for teaching, and an overall philosophy about teaching labs. Building on our previous work, which ... More
Development and Validation of the Colorado Learning Attitudes about Science Survey for Experimental PhysicsJul 10 2012As part of a comprehensive effort to transform our undergraduate physics laboratories and evaluate the impacts of these efforts, we have developed the Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS). The E-CLASS assesses ... More
The Process of Transforming an Advanced Lab Course: Goals, Curriculum, and AssessmentsJul 09 2012A thoughtful approach to designing and improving labs, particularly at the advanced level, is critical for the effective preparation of physics majors for professional work in industry or graduate school. With that in mind, physics education researchers ... More
Development and results from a survey on students views of experiments in lab classes and researchJul 22 2013The Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS) was developed as a broadly applicable assessment tool for undergraduate physics lab courses. At the beginning and end of the semester, the E-CLASS assesses students ... More
SAT Modulo Monotonic TheoriesMay 31 2014We define the concept of a monotonic theory and show how to build efficient SMT (SAT Modulo Theory) solvers, including effective theory propagation and clause learning, for such theories. We present examples showing that monotonic theories arise from ... More
Prospect for UV observations from the MoonOct 13 2014Space astronomy in the last 40 years has largely been done from spacecraft in low Earth orbit (LEO) for which the technology is proven and delivery mechanisms are readily available. However, new opportunities are arising with the surge in commercial aerospace ... More
Developing Mobility and Traffic Visualization Applications for Connected VehiclesNov 25 2018This technical report is a catalog of two applications that have been enhanced and developed to augment vehicular networking research. The first application is already described in our previous work [21], while the second one is a desktop application ... More
UV sky surveysJul 26 1998I review the development of UV and EUV astronomy, covering the spectral range from 5 to 300 nm, with emphasis on sky surveys for discrete sources. I discuss studies which resulted in lists of sources observed by imaging and deliberately omit most spectroscopic ... More
Modeling and Particle Tracking through Longitudinal Gradient Bending MagnetsOct 26 2015This report documents the development of a versatile model for longitudinal gradient bending magnets (LGB's) and its implementation in particle tracking simulations. The model presented below may be used to represent an arbitrary magnetic field profile, ... More
Intentional Design for EmpowermentAug 27 2013I argue for empowering education, adapting Marx's idea of ownership of the means of production, and discuss interactive simulations as one example of a tool in which intentional design can support student ownership of learning. I propose a model that ... More
Acyclic Colorings of Directed GraphsSep 26 2014The acyclic chromatic number of a directed graph $D$, denoted $\chi_A(D)$, is the minimum positive integer $k$ such that there exists a decomposition of the vertices of $D$ into $k$ disjoint sets, each of which induces an acyclic subgraph. For any $m ... More
The monodromy of real Bethe vectors for the Gaudin modelNov 15 2015The Bethe algebras for the Gaudin model act on the multiplicity space of tensor products of irreducible $ \mathfrak{gl}_r $-modules and have simple spectrum over real points. This fact is proved by Mukhin, Tarasov and Varchenko who also develop a relationship ... More
K-theoretic Donaldson-Thomas theory and the Hilbert scheme of points on a surfaceMay 11 2019Integrals of characteristic classes of tautological sheaves on the Hilbert scheme of points on a surface frequently arise in enumerative problems. We use the K-theoretic Donaldson-Thomas theory of certain toric Calabi-Yau threefolds to study K-theoretic ... More
Overtwisted open books from sobering arcsJul 24 2004Oct 11 2005We study open books on three manifolds which are compatible with an overtwisted contact structure. We show that the existence of certain arcs, called sobering arcs, is a sufficient condition for an open book to be overtwisted, and is necessary up to stabilization ... More
Conformal blocks and rational normal curvesDec 21 2010Jan 11 2015We prove that the Chow quotient parametrizing configurations of n points in $\mathbb{P}^d$ which generically lie on a rational normal curve is isomorphic to $\overline{M}_{0,n}$, generalizing the well-known $d = 1$ result of Kapranov. In particular, $\overline{M}_{0,n}$ ... More
Transfinite Recursion in Higher Reverse MathematicsOct 22 2013In this paper we investigate the reverse mathematics of higher-order analogues of the theory \ATRz{} within the framework of higher order reverse mathematics developed by Kohlenbach \cite{Koh01}. We define a theory \RCAzthr, a close higher-type analogue ... More
Ultraviolet Sky SurveysSep 29 1996Sep 30 1996I review the development of UV and EUV astronomy, covering the spectral range from 5 to 300 nm, with emphasis on sky surveys for discrete sources. I discuss studies which resulted in lists of sources observed by imaging. The missions are compared in terms ... More
A Fibonacci summation formula from the Verlinde formulaApr 22 2019There is a family of vector bundles over the moduli space of stable curves that, while first appearing in theoretical physics, has been an active topic of study for algebraic geometers since the 1990s. By computing the rank of the exceptional group $G_2$ ... More
A rotational approach to triple point obstructionsJul 21 2012Subfactors where the initial branching point of the principal graph is 3-valent are subject to strong constraints called triple point obstructions. Since more complicated initial branches increase the index of the subfactor, triple point obstructions ... More
The m-Degenerate Chromatic Number of a DigraphSep 26 2014Dec 04 2018The digraph chromatic number of a directed graph $D$, denoted $\chi_A(D)$, is the minimum positive integer $k$ such that there exists a partition of the vertices of $D$ into $k$ disjoint sets, each of which induces an acyclic subgraph. For any $m \geq ... More
Thinking about ArcheoastronomyMar 29 2011I discuss various aspects of archeoastronomy concentrating on physical artifacts (i.e., not including ethno-archeoastronomy) focusing on the period that ended about 2000 years ago. I present examples of artifacts interpreted as showing the interest of ... More
Quest for truly isolated galaxiesJun 23 2009I describe attempts to identify and understand the most isolated galaxies starting from my 1983 Leiden PhD thesis, continuing through a string of graduate theses on various aspects of this topic, and concluding with an up-to-date account of the difficulty ... More
The TAUVEX UV ImagerSep 30 1996I present an up-to-date description of the TAUVEX UV imager, constructed to operate on the Spectrum X-Gamma international space observatory. The projected performance and the expected scientific yield of TAUVEX are described.
Casimir Energies of Periodic Dielectric GratingsJul 17 2014Sep 23 2014Reflection of electromagnetic waves from a periodic grating can be described in terms of a discrete coupled multichannel scattering problem. By modeling the grating as a space- and frequency-dependent dielectric, it is possible to use a variable phase ... More