Results for "Jason M. Allred"

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Stimulating STDP to Exploit Locality for Lifelong Learning without Catastrophic ForgettingFeb 08 2019Stochastic gradient descent requires that training samples be drawn from a uniformly random distribution of the data. For a deployed system that must learn online from an uncontrolled and unknown environment, the ordering of input samples often fails ... More
Electron doped Ca10(Pt3As8)(Fe2As2)5 and Ca10(Pt4As8)(Fe2As2)5 - High Tc superconductors with skutterudite intermediary layersJun 10 2011It has been argued that the very high transition temperatures of the highest Tc cuprate superconductors are facilitated by enhanced CuO2 plane coupling through the (Bi,Tl,Hg)-O intermediary layers. Whether enhanced coupling through intermediary layers ... More
Investigating the response of loop plasma to nanoflare heating using RADYN simulationsApr 16 2018We present the results of 1D hydrodynamic simulations of coronal loops which are subject to nanoflares, caused by either in-situ thermal heating, or non-thermal electrons (NTE) beams. The synthesized intensity and Doppler shifts can be directly compared ... More
From Radio to X-ray: The Quiescent Atmosphere of the dMe Flare Star EV LacertaeApr 11 2006We report on multi-wavelength observations spanning radio to X-ray wavelengths of the M dwarf flare star, EV Lacertae, probing the characteristics of the outer atmospheric plasma from the upper chromosphere to the corona. We detect the star at a wavelength ... More
Brownmillerite Ca2Co2O5: Synthesis, Stability, and Re-entrant Single-Crystal-to-Single-Crystal Structural TransitionsNov 20 2014Ca2Co2O5 in the brownmillerite form was synthesized using a high-pressure optical-image floating zone furnace, and single crystals with dimensions up to 1.4x0.8x0.5 mm3 were obtained. At room temperature, Ca2Co2O5 crystallizes as a fully ordered brownmillerite ... More
ASP: Learning to Forget with Adaptive Synaptic Plasticity in Spiking Neural NetworksMar 22 2017Jun 08 2018A fundamental feature of learning in animals is the "ability to forget" that allows an organism to perceive, model and make decisions from disparate streams of information and adapt to changing environments. Against this backdrop, we present a novel unsupervised ... More
Complete Analysis of a Random Forest ModelMay 07 2018Sep 21 2018Random forests have become an important tool for improving accuracy in regression problems since their popularization by [Breiman, 2001] and others. In this paper, we revisit a random forest model originally proposed by [Breiman, 2004] and later studied ... More
Best Split Nodes for Regression TreesJun 24 2019Decision trees with binary splits are popularly constructed using Classification and Regression Trees (CART) methodology. For regression models, at each node of the tree, the data is divided into two daughter nodes according to a split point that maximizes ... More
Best Split Nodes for Regression TreesJun 24 2019Jul 15 2019Decision trees with binary splits are popularly constructed using Classification and Regression Trees (CART) methodology. For regression models, this approach recursively divides the data into two near-homogenous daughter nodes according to a split point ... More
Bulk Intergrowth of a Topological Insulator with a Room Temperature FerromagnetFeb 22 2012We demonstrate that the layered room temperature ferromagnet Fe7Se8 and the topological insulator Bi2Se3 form crystallographically oriented bulk composite intergrowth crystals. The morphology of the intergrowth in real space and reciprocal space is described. ... More
Coincident structural and magnetic order in BaFe$_2$(As$_{1-x}$)P$_x$)$_2$ revealed by high-resolution neutron diffractionOct 09 2014We present neutron diffraction analysis of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ over a wide temperature (10 to 300 K) and compositional ($0.11 \leq x \leq 0.79$) range, including the normal state, the magnetically ordered state, and the superconducting state. ... More
Charge ordering and ferrimagnetism in the strongly correlated $β$-V$_2$PO$_5$ single crystalDec 28 2017A combined study of transport, thermodynamic, neutron diffraction, nuclear magnetic resonance measurements and first principles calculation were performed for $\beta$-V$_2$PO$_5$ single crystal. It was shown to be a semiconductor with a band gap of 0.48 ... More
Counting Motifs with Graph SamplingFeb 21 2018Applied researchers often construct a network from a random sample of nodes in order to infer properties of the parent network. Two of the most widely used sampling schemes are subgraph sampling, where we sample each vertex independently with probability ... More
Estimating the Number of Connected Components in a Graph via Subgraph SamplingJan 12 2018Jun 15 2019Learning properties of large graphs from samples has been an important problem in statistical network analysis since the early work of Goodman \cite{Goodman1949} and Frank \cite{Frank1978}. We revisit a problem formulated by Frank \cite{Frank1978} of ... More
Shell Model of BaTiO3 Derived from Ab-initio Total Energy CalculationsSep 07 2013A shell model for ferroelectric perovskites fitted to results of first-principles density functional theory (DFT) calculations is strongly affected by approximations made in the exchange-correlation functional within DFT, and in general not as accurate ... More
A 3D Model of AR 11726 Heated by NanoflaresJul 02 2018The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) and the Hinode/ EUV Imaging Spectrometer (EIS) observed AR 11726 on 2013 April 23. We present intensity images in numerous atomic lines constructed from these observations. These lines are ... More
Double-Q spin-density wave in iron arsenide superconductorsMay 22 2015Elucidating the nature of the magnetic ground state of iron-based superconductors is of paramount importance in unveiling the mechanism behind their high temperature superconductivity. Until recently, it was thought that superconductivity emerges only ... More
Detailed magnetic and structural analysis mapping a robust magnetic C4 dome in Sr1-xNaxFe2As2Jan 21 2016The recently discovered $C_4$ tetragonal magnetic phase in hole-doped members of the iron-based superconductors provides new insights into the origin of unconventional superconductivity. Previously observed in Ba$_{1-x}A_x$Fe$_2$As$_2$ (with $A =$ K, ... More
Halpha line profile asymmetries and the chromospheric flare velocity fieldOct 07 2015The asymmetries observed in the line profiles of solar flares can provide important diagnostics of the properties and dynamics of the flaring atmosphere. In this paper the evolution of the Halpha and Ca II 8542 {\AA} lines are studied using high spatial, ... More
Structural, Magnetic, and Superconducting Properties of Ba1-xNaxFe2As2Sep 30 2013We report the results of a systematic investigation of the phase diagram of the iron-based superconductor system, Ba1-xNaxFe2As2, from x = 0.1 to x = 1.0 using high resolution neutron and x-ray diffraction and magnetization measurements. We find that ... More
Single-Shot Terahertz Time-Domain Spectroscopy in Pulsed High Magnetic FieldsAug 29 2016We have developed a single-shot terahertz time-domain spectrometer to perform optical pump/terahertz probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective ... More
Single-Shot Terahertz Time-Domain Spectroscopy in Pulsed High Magnetic FieldsAug 29 2016Oct 12 2016We have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective ... More
Atom interferometric gravitational wave detection using heterodyne laser linksJan 27 2015We propose a scheme based on a heterodyne laser link that allows for long baseline gravitational wave detection using atom interferometry. While the baseline length in previous atom-based proposals is constrained by the need for a reference laser to remain ... More
Local Structure Controlling the Glass Transition in a Prototype Metal-Metalloid GlassJan 21 2019We use a structure analysis technique that quantifies cluster geometries using machine learning to identify a bicapped square antiprism (BSAP) as the nearest-neighbor cluster involved in the glass transition in Pd82Si18, a prototype metal-metalloid metallic ... More
Minimax Lower Bounds for Ridge Combinations Including Neural NetsFeb 09 2017Estimation of functions of $ d $ variables is considered using ridge combinations of the form $ \textstyle\sum_{k=1}^m c_{1,k} \phi(\textstyle\sum_{j=1}^d c_{0,j,k}x_j-b_k) $ where the activation function $ \phi $ is a function with bounded value and ... More
Finite-sample risk bounds for maximum likelihood estimation with arbitrary penaltiesDec 29 2017The MDL two-part coding $ \textit{index of resolvability} $ provides a finite-sample upper bound on the statistical risk of penalized likelihood estimators over countable models. However, the bound does not apply to unpenalized maximum likelihood estimation ... More
Fermi surface topology and low-lying electronic structure of a new iron-based superconductor Ca10(Pt3As8)(Fe2As2)5Oct 21 2011We report a first study of low energy electronic structure and Fermi surface topology for the recently discovered iron-based superconductor Ca10(Pt3As8)(Fe2As2)5 (the 10-3-8 phase, with Tc = 8K), via angle-resolved photoemission spectroscopy (ARPES). ... More
A Consistent Effective Theory of Long-Wavelength Cosmological PerturbationsOct 10 2013Nov 06 2013Effective field theory provides a perturbative framework to study the evolution of cosmological large-scale structure. We investigate the underpinnings of this approach, and suggest new ways to compute correlation functions of cosmological observables. ... More
Density distributions and depth in flocksFeb 21 2019Recent experimental evidence suggests that interactions in flocks of birds do not involve a characteristic length scale. Bird flocks have also been revealed to have an inhomogeneous density distribution, with the density of birds near the border greater ... More
On the Minimum Ropelength of Knots and LinksMar 30 2001Mar 01 2002The ropelength of a knot is the quotient of its length and its thickness, the radius of the largest embedded normal tube around the knot. We prove existence and regularity for ropelength minimizers in any knot or link type; these are $C^{1,1}$ curves, ... More
Risk Bounds for High-dimensional Ridge Function Combinations Including Neural NetworksJul 05 2016Oct 29 2018Let $ f^{\star} $ be a function on $ \mathbb{R}^d $ with an assumption of a spectral norm $ v_{f^{\star}} $. For various noise settings, we show that $ \mathbb{E}\|\hat{f} - f^{\star} \|^2 \leq \left(v^4_{f^{\star}}\frac{\log d}{n}\right)^{1/3} $, where ... More
Statistical Guarantees for Estimating the Centers of a Two-component Gaussian Mixture by EMAug 07 2016Recently, a general method for analyzing the statistical accuracy of the EM algorithm has been developed and applied to some simple latent variable models [Balakrishnan et al. 2016]. In that method, the basin of attraction for valid initialization is ... More
Hubble Space Telescope Far Ultraviolet Spectroscopy of the Dwarf Nova VW Hyi in SuperoutburstMar 02 2007We obtained three consecutive HST spectroscopic observations of a single superoutburst of the dwarf nova VW Hydri. The spectra cover the beginning, middle, and end of the superoutburst. All of the spectra are dominated by strong absorption lines due to ... More
Information Security Plan for Flight Simulator ApplicationsNov 07 2011The Department of Defense has a need for an identity management system that uses two factor authentications to ensure that only the correct individuals get access to their top secret flight simulator program. Currently the Department of Defense does not ... More
The structure of hypersonic shock waves using Navier-Stokes equations modified to include mass diffusionJun 01 2007Howard Brenner has recently proposed modifications to the Navier-Stokes equations that relate to a diffusion of fluid volume that would be significant for flows with high density gradients. In a previous paper (Greenshields & Reese, 2007), we found these ... More
A volume-based hydrodynamic approach to sound wave propagation in a monatomic gasJul 17 2009Jul 31 2009We investigate sound wave propagation in a monatomic gas using a volume-based hydrodynamic model. In Physica A vol 387(24) (2008) pp6079-6094, a microscopic volume-based kinetic approach was proposed by analyzing molecular spatial distributions; this ... More
On prime non-primitive von Neumann regular algebrasMar 21 2011Let $E$ be any directed graph, and $K$ any field. We classify those graphs $E$ for which the Leavitt path algebra $L_K(E)$ is primitive. As a consequence, we obtain classes of examples of von Neumann regular prime rings which are not primitive.
Approximation by Combinations of ReLU and Squared ReLU Ridge Functions with $ \ell^1 $ and $ \ell^0 $ ControlsJul 26 2016May 23 2018We establish $ L^{\infty} $ and $ L^2 $ error bounds for functions of many variables that are approximated by linear combinations of ReLU (rectified linear unit) and squared ReLU ridge functions with $ \ell^1 $ and $ \ell^0 $ controls on their inner and ... More
Magnetically-Driven Suppression of Nematic Order in an Iron-Based SuperconductorMar 11 2013Feb 17 2015A theory of superconductivity in the iron-based materials requires an understanding of the phase diagram of the normal state. In these compounds, superconductivity emerges when stripe spin density wave (SDW) order is suppressed by doping, pressure or ... More
Extreme Sensitivity of Superconductivity to Stoichiometry in FeSe (Fe1+dSe)Nov 11 2008Feb 02 2009The recently discovered iron arsenide superconductors, which display superconducting transition temperatures as high as 55 K, appear to share a number of general features with high-Tc cuprates, including proximity to a magnetically ordered state and robustness ... More
Lyapunov Exponent of Rank One Matrices: Ergodic Formula and Inapproximability of the Optimal DistributionMay 18 2019The Lyapunov exponent corresponding to a set of square matrices $\mathcal{A} = \{A_1, \dots, A_n \}$ and a probability distribution $p$ over $\{1, \dots, n\}$ is $\lambda(\mathcal{A},p) := \lim_{k \to \infty} \frac{1}{k} \,\mathbb{E} \log \|A_{\sigma_k} ... More
On the uniqueness of promotion operators on tensor products of type A crystalsJun 19 2008May 05 2009The affine Dynkin diagram of type $A_n^{(1)}$ has a cyclic symmetry. The analogue of this Dynkin diagram automorphism on the level of crystals is called a promotion operator. In this paper we show that the only irreducible type $A_n$ crystals which admit ... More
Ruprecht 147: The oldest nearby open cluster as a new benchmark for stellar astrophysicsJun 27 2012Jan 05 2013Ruprecht 147 is a hitherto unappreciated open cluster that holds great promise as a standard in fundamental stellar astrophysics. We have conducted a radial velocity survey of astrometric candidates with Lick, Palomar, and MMT observatories and have identified ... More
Modelling Mg II During Solar Flares, I: Partial Frequency Redistribution, Opacity, and Coronal IrradiationAug 14 2019The Interface Region Imaging Spectrograph (IRIS) has routinely observed the flaring Mg II NUV spectrum, offering excellent diagnostic potential and a window into the location of energy deposition. A number of studies have forward modelled both the general ... More
Multi-robot Dubins Coverage with Autonomous Surface VehiclesAug 07 2018In large scale coverage operations, such as marine exploration or aerial monitoring, single robot approaches are not ideal, as they may take too long to cover a large area. In such scenarios, multi-robot approaches are preferable. Furthermore, several ... More
The Definitive Abundance of Interstellar OxygenOct 15 1997Using the Goddard High Resolution Spectrograph (GHRS) onboard HST, we have obtained high S/N echelle observations of the weak interstellar O I 1356 A absorption toward the stars Gamma Cas, Epsilon Per, Delta Ori, Epsilon Ori, 15 Mon, Tau CMa, and Gamma ... More
Light-pulse atom interferometryJun 19 2008The light-pulse atom interferometry method is reviewed. Applications of the method to inertial navigation and tests of the Equivalence Principle are discussed.
Theory of Rabi interaction between an infrared-active phonon and cavity-resonant modesDec 29 2006Jan 05 2007We present the theory of interaction between a polar vibration in a semiconductor and an electromagnetic mode of a surrounding cavity. Tuning the cavity frequency near the transverse optical phonon frequency couples the phonon-induced polarization field ... More
The graphs with all but two eigenvalues equal to $-2$ or $0$Jan 21 2016Jul 08 2016We determine all graphs for which the adjacency matrix has at most two eigenvalues (multiplicities included) not equal to $-2$, or $0$, and determine which of these graphs are determined by their adjacency spectrum.
The Second Hull of a Knotted CurveApr 10 2002Mar 26 2003The convex hull of a set K in space consists of points which are, in a certain sense, "surrounded" by K. When K is a closed curve, we define its higher hulls, consisting of points which are "multiply surrounded" by the curve. Our main theorem shows that ... More
Stovepiping and Malicious Software: A Critical Review of AGI ContainmentNov 08 2018Awareness of the possible impacts associated with artificial intelligence has risen in proportion to progress in the field. While there are tremendous benefits to society, many argue that there are just as many, if not more, concerns related to advanced ... More
What does my knowing your plans tell me?Oct 09 2018For robots acting in the presence of observers, we examine the information that is divulged if the observer is party to the robot's plan. Privacy constraints are specified as the stipulations on what can be inferred during plan execution. We imagine a ... More
Finding plans subject to stipulations on what information they divulgeSep 25 2018Motivated by applications where privacy is important, we consider planning problems for robots acting in the presence of an observer. We first formulate and then solve planning problems subject to stipulations on the information divulged during plan execution---the ... More
How Decoherence Affects the Probability of Slow-Roll Eternal InflationDec 15 2016May 09 2017Slow-roll inflation can become eternal if the quantum variance of the inflaton field around its slowly rolling classical trajectory is converted into a distribution of classical spacetimes inflating at different rates, and if the variance is large enough ... More
Spectral Energy Distributions of Weak Active Galactic Nuclei Associated With Low-Ionization Nuclear Emission RegionsJan 17 2010We present a compilation of spectral energy distributions of 35 weak AGNs in LINERs using recent data from the published literature. We make use of previously published compilations of data, after complementing and extending them with more recent data. ... More
Altmetrics in the wild: Using social media to explore scholarly impactMar 20 2012In growing numbers, scholars are integrating social media tools like blogs, Twitter, and Mendeley into their professional communications. The online, public nature of these tools exposes and reifies scholarly processes once hidden and ephemeral. Metrics ... More
Unambiguous separation of the inverse spin Hall and anomalous Nernst Effects within a ferromagnetic metal using the spin Seebeck effectJul 24 2014The longitudinal spin Seebeck effect is measured on the ferromagnetic insulator Fe$_3$O$_4$ with the ferromagnetic metal Co$_{0.2}$Fe$_{0.6}$B$_{0.2}$ (CoFeB) as the spin detector. By using a non-magnetic spacer material between the two materials (Ti), ... More
The graphs with all but two eigenvalues equal to $\pm 1$Oct 24 2013We determine all graphs whose adjacency matrix has at most two eigenvalues (multiplicities included) different from $\pm 1$ and decide which of these graphs are determined by their spectrum. This includes the so-called friendship graphs, which consist ... More
Secular and orbital variability of Cir X-1 observed in optical spectraSep 11 2001We have observed variations in the optical emission lines from the X-ray binary Circinus X-1. These variations may be attributed both to orbital variations and to long term secular changes in line strength. We have detected double-peaked H-alpha emission ... More
Lagrangian Relaxation for MAP Estimation in Graphical ModelsSep 28 2007We develop a general framework for MAP estimation in discrete and Gaussian graphical models using Lagrangian relaxation techniques. The key idea is to reformulate an intractable estimation problem as one defined on a more tractable graph, but subject ... More
Measurements of trap dynamics of cold OH molecules using resonance enhanced multiphoton ionizationMay 17 2017Trapping cold, chemically important molecules with electromagnetic fields is a useful technique to study small molecules and their interactions. Traps provide long interaction times that are needed to precisely examine these low density molecular samples. ... More
Constraints and tensions in testing general relativity from Planck and CFHTLenS including intrinsic alignment systematicsJan 13 2015Jun 19 2015We present constraints on testing general relativity (GR) at cosmological scales using recent data sets and assess the impact of galaxy intrinsic alignment (IA) in the CFHTLenS lensing data on those constraints. We consider CMB temperature data from Planck, ... More
A Generalized Muon Trajectory Estimation Algorithm with Energy Loss for Application to Muon TomographyJan 23 2018This work presents a generalized muon trajectory estimation (GMTE) algorithm to estimate the path of a muon in either uniform or nonuniform media. The use of cosmic ray muons in nuclear nonproliferation and safeguards verification applications has recently ... More
RRT+ : Fast Planning for High-Dimensional Configuration SpacesDec 21 2016Dec 24 2016In this paper we propose a new family of RRT based algorithms, named RRT+ , that are able to find faster solutions in high-dimensional configuration spaces compared to other existing RRT variants by finding paths in lower dimensional subspaces of the ... More
Demonstration of a Cold Atom Fountain Electron Electric Dipole Moment ExperimentFeb 01 2006Mar 14 2006A Cs fountain electron electric dipole moment (EDM) experiment using electric-field quantization is demonstrated. With magnetic fields reduced to 200 pT or less, the electric field lifts the degeneracy between hyperfine levels of different|mF| and, along ... More
The Bayesian Second Law of ThermodynamicsAug 10 2015Apr 03 2017We derive a generalization of the Second Law of Thermodynamics that uses Bayesian updates to explicitly incorporate the effects of a measurement of a system at some point in its evolution. By allowing an experimenter's knowledge to be updated by the measurement ... More
Deep Searches for Radio Pulsations and Bursts from Four Southern Anomalous X-ray PulsarsMar 11 2007We have searched for persistent radio pulsations, bright single pulses, and bursts from four Southern anomalous X-ray pulsars (AXPs). Deep observations were conducted at 1.4 GHz in 1999 July and August with the Parkes 64-m telescope. For all of the target ... More
Cyber Security Awareness Campaigns: Why do they fail to change behaviour?Jan 09 2019The present paper focuses on Cyber Security Awareness Campaigns, and aims to identify key factors regarding security which may lead them to failing to appropriately change people's behaviour. Past and current efforts to improve information-security practices ... More
Anatomy of $\varepsilon'/\varepsilon$ beyond the Standard ModelAug 01 2018Aug 07 2019We present for the first time a model-independent anatomy of the ratio $\varepsilon'/\varepsilon$ in the context of the $\Delta S = 1$ effective theory with operators invariant under QCD and QED and in the context of the Standard Model Effective Field ... More
Competitive Exclusion in a DAE Model for Microbial Electrolysis CellsJun 05 2019Microbial electrolysis cells (MECs) are devices that employ electroactive bacteria to perform extracellular electron transfer, enabling hydrogen generation from biodegradable substrates. Previously we analyzed a regular, semi-explicit, index 1 differential-algebraic ... More
Estimating the Coefficients of a Mixture of Two Linear Regressions by Expectation MaximizationApr 26 2017Oct 16 2018We give convergence guarantees for estimating the coefficients of a symmetric mixture of two linear regressions by expectation maximization (EM). In particular, we show that the empirical EM iterates converge to the target parameter vector at the parametric ... More
Topological Surface States and Dirac point tuning in ternary Bi2Te2Se class of topological insulatorsJun 04 2012Dec 14 2012Using angle-resolved photoemission spectroscopy, we report electronic structure for representative members of ternary topological insulators. We show that several members of this family, such as Bi2Se2Te, Bi2Te2Se, and GeBi2Te4, exhibit a singly degenerate ... More
Structural and magnetic phase transitions in Ca$_{0.73}$La$_{0.27}$FeAs$_2$ with electron overdoped FeAs layersMay 21 2015Mar 14 2016We report a study of the Ca$_{0.73}$La$_{0.27}$FeAs$_2$ single crystals. We unravel a monoclinic to triclinic phase transition at 58 K, and a paramagnetic to stripe antiferromagnetic (AFM) phase transition at 54 K, below which spins order 45$^\circ$ away ... More
Modeling Mg II h, k and Triplet Lines at Solar Flare RibbonsApr 28 2019Observations from the \textit{Interface Region Imaging Spectrograph} (\textsl{IRIS}) often reveal significantly broadened and non-reversed profiles of the Mg II h, k and triplet lines at flare ribbons. To understand the formation of these optically thick ... More
Weak Gravitational Lensing Systematics from Image CombinationOct 12 2013Extremely accurate shape measurements of galaxy images are needed to probe dark energy properties with weak gravitational lensing surveys. To increase survey area with a fixed observing time and pixel count, images from surveys such as the Wide Field ... More
A new cohomological formula for helicity in $\R^{2k+1}$ reveals the effect of a diffeomorphism on helicityMar 08 2009Oct 26 2012The helicity of a vector field is a measure of the average linking of pairs of integral curves of the field. Computed by a six-dimensional integral, it is widely useful in the physics of fluids. For a divergence-free field tangent to the boundary of a ... More
Optimality and Approximation with Policy Gradient Methods in Markov Decision ProcessesAug 01 2019Policy gradient methods are among the most effective methods in challenging reinforcement learning problems with large state and/or action spaces. However, little is known about even their most basic theoretical convergence properties, including: if and ... More
Leavitt path algebras satisfying a polynomial identityAug 17 2014Leavitt path algebras L of an arbitrary graph E over a field K satisfying a polynomial identity are completely characterized both in graph-theoretic and algebraic terms. When E is a finite graph, L satisfying a polynomial identity is shown to be equivalent ... More
Estimation of convex supports from noisy measurementsApr 26 2018A popular class of problem in statistics deals with estimating the support of a density from $n$ observations drawn at random from a $d$-dimensional distribution. The one-dimensional case reduces to estimating the end points of a univariate density. In ... More
Enhanced atom interferometer readout through the application of phase shearMay 14 2013We present a method for determining the phase and contrast of a single shot of an atom interferometer. The application of a phase shear across the atom ensemble yields a spatially varying fringe pattern at each output port, which can be imaged directly. ... More
Riverine Coverage with an Autonomous Surface Vehicle over Known EnvironmentsAug 07 2019Environmental monitoring and surveying operations on rivers currently are performed primarily with manually-operated boats. In this domain, autonomous coverage of areas is of vital importance, for improving both the quality and the efficiency of coverage. ... More
The classification of compact simply connected biquotients in dimension 4 and 5Apr 05 2013Apr 15 2014We classify all compact simply connected biquotients of dimension 4 and 5. In particular, all pairs of groups $(G,H)$ and embeddings $H\rightarrow G\times G$ giving rise to a particular biquotient are classified.
Weak Convergence of the Scaled Median of Independent Brownian MotionsJul 26 2005Aug 02 2006We consider the median of n independent Brownian motions, and show that this process, when properly scaled, converges weakly to a centered Gaussian process. The chief difficulty is establishing tightness, which is proved through direct estimates on the ... More
The number of small blocks in exchangeable random partitionsNov 09 2009Jul 12 2010Suppose $\Pi$ is an exchangeable random partition of the positive integers and $\Pi_n$ is its restriction to $\{1, ..., n\}$. Let $K_n$ denote the number of blocks of $\Pi_n$, and let $K_{n,r}$ denote the number of blocks of $\Pi_n$ containing $r$ integers. ... More
Stillman's Question for Exterior Algebras and Herzog's Conjecture on Betti Numbers of Syzygy ModulesJul 30 2013Jan 24 2018Let K be a field of characteristic 0 and consider exterior algebras of finite dimensional K-vector spaces. In this short paper we exhibit principal quadric ideals in a family whose Castelnuovo-Mumford regularity is unbounded. This negatively answers the ... More
A Polynomial Bound on the Regularity of an Ideal in Terms of Half of the SyzygiesDec 01 2011Let K be a field and let S = K[x_1, ..., x_n] be a polynomial ring. Consider a homogenous ideal I in S. Let t_i denote reg(Tor_i (S/I, K)), the maximal degree of an ith syzygy of S/I. We prove bounds on the numbers t_i for i > n/2 purely in terms of the ... More
Rigorous results for a population model with selection II: genealogy of the populationJul 01 2015We consider a model of a population of fixed size $N$ undergoing selection. Each individual acquires beneficial mutations at rate $\mu_N$, and each beneficial mutation increases the individual's fitness by $s_N$. Each individual dies at rate one, and ... More
The loop-erased random walk and the uniform spanning tree on the four-dimensional discrete torusFeb 23 2006Jul 29 2007Let x and y be points chosen uniformly at random from $\Z_n^4$, the four-dimensional discrete torus with side length n. We show that the length of the loop-erased random walk from x to y is of order $n^2 (\log n)^{1/6}$, resolving a conjecture of Benjamini ... More
A $2$-compact group as a spetsJun 03 2019Jun 20 2019In 1998 Malle introduced spetses which are mysterious objects with non-real Weyl groups. In algebraic topology, a $p$-compact group $\mathbf{X}$ is a space which is a homotopy-theoretic $p$-local analogue of a compact Lie group. A connected $p$-compact ... More
T-structures on elliptic fibrationsSep 10 2015We consider t-structures that naturally arise on elliptic fibrations. By filtering the category of coherent sheaves on an elliptic fibration using the torsion pairs corresponding to these t-structures, we prove results describing equivalences of t-structures ... More
Moduli of PT-semistable objects IINov 29 2010May 04 2011We generalise the techniques of semistable reduction for flat families of sheaves to the setting of the derived category $D^b(X)$ of coherent sheaves on a smooth projective three-fold $X$. Then we construct the moduli of PT-semistable objects in $D^b(X)$ ... More
The minimum rank problem over finite fieldsJan 18 2008The structure of all graphs having minimum rank at most k over a finite field with q elements is characterized for any possible k and q. A strong connection between this characterization and polarities of projective geometries is explained. Using this ... More
Fourier-Mukai transforms of slope stable torsion-free sheaves and stable 1-dimensional sheaves on Weierstrass elliptic threefoldsOct 10 2017We focus on a class of Weierstrass elliptic threefolds that allows the base of the fibration to be a Fano surface or a numerically $K$-trivial surface. In the first half of this article, we define the notion of limit tilt stability, which is closely related ... More
Si IV Resonance Line Emission During Solar Flares: Non-LTE, Non-equilibrium, Radiation Transfer SimulationsNov 27 2018The Interface Region Imaging Spectrograph (IRIS) routinely observes the Si IV resonance lines. When analyzing observations of these lines it has typically been assumed they form under optically thin conditions. This is likely valid for the quiescent Sun, ... More
Simulations of the Mg II k and Ca II 8542 lines from an Alfvén Wave-heated flare chromosphereMay 19 2016We use radiation hydrodynamic simulations to examine two models of solar flare chromospheric heating: Alfv\'en wave dissipation and electron beam collisional losses. Both mechanisms are capable of strong chromospheric heating, and we show that the distinctive ... More
Time Series Anomaly Detection; Detection of anomalous drops with limited features and sparse examples in noisy highly periodic dataAug 11 2017Google uses continuous streams of data from industry partners in order to deliver accurate results to users. Unexpected drops in traffic can be an indication of an underlying issue and may be an early warning that remedial action may be necessary. Detecting ... More
On the Apparent Orbital Inclination Change of the Extrasolar Transiting Planet TrES-2bJul 09 2009Mar 13 2010On June 15, 2009 UT the transit of TrES-2b was detected using the University of Arizona's 1.55 meter Kuiper Telescope with 2.0-2.5 millimag RMS accuracy in the I-band. We find a central transit time of $T_c = 2454997.76286 \pm0.00035$ HJD, an orbital ... More
Optical Lattices as Waveguides and Beam Splitters for Atom Interferometry: An Analytical Treatment and Proposal of ApplicationsOct 19 2009Feb 25 2010We provide an analytical description of the dynamics of an atom in an optical lattice using the method of perturbative adiabatic expansion. A precise understanding of the lattice-atom interaction is essential to taking full advantage of the promising ... More
Long-Term Radio Timing Observations of the Transition Millisecond Pulsar PSR~J1023+0038Nov 20 2013The radio millisecond pulsar PSR J1023+0038 exhibits complex timing and eclipse behavior. Here we analyze four years' worth of radio monitoring observations of this object. We obtain a long-term timing solution, albeit with large residual timing errors ... More
Spectroscopy of the inner companion of the pulsar PSR J0337+1715Feb 03 2014Feb 04 2014The hierarchical triple system PSR J0337+1715 offers an unprecedented laboratory to study secular evolution of interacting systems and to explore the complicated mass-transfer history that forms millisecond pulsars and helium-core white dwarfs. The latter ... More