Results for "S. McKeown Walker"

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ARPES Studies of Two-Dimensional Electron Gases at Transition Metal Oxide SurfacesDec 12 2016High mobility two-dimensional electron gases (2DEGs) underpin today's silicon based devices and are of fundamental importance for the emerging field of oxide electronics. Such 2DEGs are usually created by engineering band offsets and charge transfer at ... More
Band Structure and Spin-Orbital Texture of the (111)-KTaO3 Two-Dimensional Electron GasMar 14 2019Two-dimensional electron gases (2DEGs) in oxides show great potential for discovering new physical phenomena and at the same time hold promise for electronic applications. In this work we use angle resolved photoemission to determine the electronic structure ... More
Quasiparticle dynamics and spin-orbital texture of the SrTiO3 two-dimensional electron gasMar 03 2014Sep 07 2014Two-dimensional electron gases (2DEGs) in SrTiO$_3$ have become model systems for engineering emergent behaviour in complex transition metal oxides. Understanding the collective interactions that enable this, however, has thus far proved elusive. Here ... More
Control of a two-dimensional electron gas on SrTiO3(111) by atomic oxygenMay 13 2014We report on the formation of a two-dimensional electron gas (2DEG) at the bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments reveal highly itinerant carriers with a 6-fold symmetric Fermi surface and strongly anisotropic ... More
Controlling bulk conductivity in topological insulators: Key role of anti-site defectsApr 18 2012The binary Bi-chalchogenides, Bi2Ch3, are widely regarded as model examples of a recently discovered new form of quantum matter, the three-dimensional topological insulator (TI) [1-4]. These compounds host a single spin-helical surface state which is ... More
Observation of Large Topologically Trivial Fermi-Arcs in the Candidate Type-II Weyl Semimetal WTe2Apr 08 2016Sep 12 2016We report angle-resolved photoemission experiments resolving the distinct electronic structure of the inequivalent top and bottom (001) surfaces of WTe2. On both surfaces, we identify a surface state that forms a large Fermi-arc emerging out of the bulk ... More
Absence of Giant Spin Splitting in the Two-Dimensional Electron Liquid at the Surface of SrTiO$_3$ (001)Mar 01 2016We reinvestigate the putative giant spin splitting at the surface of SrTiO$_3$ reported by Santander-Syro $et~al.$ [Nature Mat. 13, 1085 (2014)]. Our spin- and angle-resolved photoemission experiments on (001) oriented surfaces supporting a two-dimensional ... More
Electronic structure of buried LaNiO3 layers in (111)-oriented LaNiO3/LaMnO3 superlattices probed by soft x-ray ARPESNov 25 2016Taking advantage of the large electron escape depth of soft x-ray angle resolved photoemission spectroscopy we report electronic structure measurements of (111)-oriented [LaNiO3/LaMnO3] superlattices and LaNiO3 epitaxial films. For thin films we observe ... More
Collapse of the Mott gap and emergence of a nodal liquid in lightly doped Sr$_2$IrO$_4$Jun 01 2015Superconductivity in underdoped cuprates emerges from an unusual electronic state characterised by nodal quasiparticles and an antinodal pseudogap. The relation between this state and superconductivity is intensely studied but remains controversial. The ... More
Atomically precise lateral modulation of a two-dimensional electron liquid in anatase TiO2 thin filmsMar 01 2017Engineering the electronic band structure of two-dimensional electron liquids (2DELs) confined at the surface or interface of transition metal oxides is key to unlocking their full potential. Here we describe a new approach to tailoring the electronic ... More
Spectroscopic evidence for polaronic behaviour of the strong spin-orbit insulator Sr$_3$Ir$_2$O$_7$Feb 02 2013We investigate the bilayer Ruddlesden-Popper iridate Sr$_3$Ir$_2$O$_7$ by temperature-dependent angle-resolved photoemission. We find a narrow-gap correlated insulator, with spectral features indicative of a polaronic ground state, strikingly similar ... More
High-resolution photoemission on Sr2RuO4 reveals correlation-enhanced effective spin-orbit coupling and dominantly local self-energiesDec 16 2018May 07 2019We explore the interplay of electron-electron correlations and spin-orbit coupling in the model Fermi liquid Sr2RuO4 using laser-based angle-resolved photoemission spectroscopy. Our precise measurement of the Fermi surface confirms the importance of spin-orbit ... More
Tailoring the nature and strength of electron-phonon interactions in the SrTiO$_3$(001) two-dimensional electron liquidJun 03 2015Feb 19 2016Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO$_3$(001) ... More
A weakly correlated Fermi liquid state with a small Fermi surface in lightly doped Sr$_3$Ir$_2$O$_7$Sep 24 2014We characterize the electron doping evolution of (Sr$_{1-x}$La$_x$)$_3$Ir$_2$O$_7$ by means of angle-resolved photoemission. Concomitant with the metal insulator transition around $x\approx0.05$ we find the emergence of coherent quasiparticle states forming ... More
Exponential map and normal form for cornered asymptotically hyperbolic metricsSep 30 2016This paper considers asymptotically hyperbolic manifolds with a finite boundary intersecting the usual infinite boundary -- cornered asymptotically hyperbolic manifolds -- and proves a theorem of Cartan-Hadamard type near infinity for the normal exponential ... More
Jefferson Lab Science, Past and FutureDec 03 2014The Continuous Electron Beam Accelerator Facility (CEBAF) and associated experimental equipment at Jefferson Lab comprise a unique facility for experimental nuclear physics. This facility is presently being upgraded, which will enable a new experimental ... More
Formal theory of cornered asymptotically hyperbolic Einstein metricsAug 08 2017This paper makes a formal study of asymptotically hyperbolic Einstein metrics given, as conformal infinity, a conformal manifold with boundary. The space on which such an Einstein metric exists thus has a finite boundary in addition to the usual infinite ... More
SMARTies: Sentiment Models for Arabic Target EntitiesJan 12 2017We consider entity-level sentiment analysis in Arabic, a morphologically rich language with increasing resources. We present a system that is applied to complex posts written in response to Arabic newspaper articles. Our goal is to identify important ... More
Aligning Noisy Parallel Corpora Across Language Groups : Word Pair Feature Matching by Dynamic Time WarpingSep 22 1994We propose a new algorithm called DK-vec for aligning pairs of Asian/Indo-European noisy parallel texts without sentence boundaries. DK-vec improves on previous alignment algorithms in that it handles better the non-linear nature of noisy corpora. The ... More
Modeling with a Large Class of Unimodal Multivariate DistributionsJun 24 2015In this paper we introduce a new class of multivariate unimodal distributions, motivated by Khintchine's representation. We start by proposing a univariate model, whose support covers all the unimodal distributions on the real line. The proposed class ... More
Applications for edge detection techniques using Chandra and XMM-Newton data: galaxy clusters and beyondJun 03 2016The unrivalled spatial resolution of the Chandra X-ray observatory has allowed many breakthroughs to be made in high energy astrophysics. Here we explore applications of Gaussian Gradient Magnitude (GGM) filtering to X-ray data, which dramatically improves ... More
Large scale gas sloshing out to half the virial radius in the strongest cool core REXCESS galaxy cluster, RXJ2014.8-2430Feb 27 2014We search the cool core galaxy clusters in the REXCESS sample for evidence of large scale gas sloshing, and find clear evidence for sloshing in RXJ2014.8-2430, the strongest cool core cluster in the REXCESS cluster sample. The residuals of the surface ... More
Constraining gas motions in the Centaurus cluster using X-ray surface brightness fluctuations and metal diffusionAug 18 2015We compare two different methods of constraining the characteristic velocity and spatial scales of gas motions in the X-ray bright, nearby Centaurus cluster, using new deep (760ks) Chandra observations. The power spectrum of excess surface brightness ... More
What fraction of the density fluctuations in the Perseus cluster core is due to gas sloshing rather than AGN feedback?Aug 30 2018Deep Chandra observations of the core of the Perseus cluster show a plethora of complex structure. It has been found that when the observed density fluctuations in the intracluster medium are converted into constraints on AGN induced turbulence, the resulting ... More
The quantum AdS_5 x S^5 superstring at finite couplingAug 22 2013The integrability of string theory in AdS_5 x S^5 and of the dilatation operator of N=4 super-Yang-Mills theory has been used to propose an exact solution to the spectral problem in these theories. Weak coupling perturbation theory both in gauge theory ... More
Nonparametric Bayesian testing for monotonicityApr 11 2013Jun 01 2014This paper studies the problem of testing whether a function is monotone from a nonparametric Bayesian perspective. Two new families of tests are constructed. The first uses constrained smoothing splines, together with a hierarchical stochastic-process ... More
Neutron Calibration Sources in the Daya Bay ExperimentApr 29 2015We describe the design and construction of the low rate neutron calibration sources used in the Daya Bay Reactor Anti-neutrino Experiment. Such sources are free of correlated gamma-neutron emission, which is essential in minimizing induced background ... More
Exploring the origin of a large cavity in Abell 1795 using deep Chandra observationsSep 23 2014We examine deep stacked Chandra observations of the galaxy cluster Abell 1795 (over 700ks) to study in depth a large (34 kpc radius) cavity in the X-ray emission. Curiously, despite the large energy required to form this cavity (4PV=4x10^60 erg), there ... More
Relaxation of Spin Polarized $^3$He in Mixtures of $^3$He and $^4$He Below the $^4$He Lambda PointMar 21 2006Apr 08 2008We report the first study of the depolarization behavior of spin polarized 3He in a mixture of 3He-4He at a temperature below the 4He Lambda point in a deuterated TetraPhenyl Butadiene-doped deuterated PolyStyrene (dTPB-dPS) coated acrylic cell. In our ... More
Systematics of two-component superconductivity in $YBa_{2}Cu_{3}O_{6.95}$ from microwave measurements of high quality single crystalsSep 06 1997Systematic microwave surface impedance measurements of YBCO single crystals grown in $BaZrO_3$ crucibles reveal new properties that are not directly seen in similar measurements of other YBCO samples. Two key observations obtained from complex conductivity ... More
Measurement and feedback for cooling heavy levitated particles in low frequency trapsMar 25 2019We consider a possible route to ground state cooling of a levitated nanoparticle, magnetically trapped by a strong permanent magnet, using a combination of measurement and feedback. The trap frequency of this system is much lower than those involving ... More
Gathering Statistics to Aspectually Classify Sentences with a Genetic AlgorithmOct 21 1996This paper presents a method for large corpus analysis to semantically classify an entire clause. In particular, we use cooccurrence statistics among similar clauses to determine the aspectual class of an input clause. The process examines linguistic ... More
Content Selection in Deep Learning Models of SummarizationOct 29 2018Feb 18 2019We carry out experiments with deep learning models of summarization across the domains of news, personal stories, meetings, and medical articles in order to understand how content selection is performed. We find that many sophisticated features of state ... More
X-ray observations of the galaxy cluster Abell 2029 to the virial radiusMar 02 2012We present Suzaku observations of the galaxy cluster Abell 2029, which exploit Suzaku's low particle background to probe the ICM to radii beyond those possible with previous observations (reaching out to the virial radius), and with better azimuthal coverage. ... More
The Cryogenic Target for the G$^0$ Experiment at Jefferson LabFeb 23 2005A cryogenic horizontal single loop target has been designed, built, tested and operated for the G$^0$ experiment in Hall C at Jefferson Lab. The target cell is 20 cm long, the loop volume is 6.5 l and the target operates with the cryogenic pump fully ... More
The effect of the quasar H1821+643 on the surrounding intracluster medium: revealing the underlying cooling flowMay 29 2014We present a detailed study of the thermodynamic properties of the intracluster medium of the only low redshift galaxy cluster to contain a highly luminous quasar, H1821+643. The cluster is a highly massive, strong cool core cluster. We find that the ... More
Gowers norms control diophantine inequalitiesMar 02 2017Nov 03 2018A central tool in the study of systems of linear equations with integer coefficients is the Generalised von Neumann Theorem of Green and Tao. This theorem reduces the task of counting the weighted solutions of these equations to that of counting the weighted ... More
Universal properties of bicategories of polynomialsJun 27 2018Dec 23 2018We establish the universal properties of the bicategory of polynomials, considering both cartesian and general morphisms between these polynomials. A direct proof of these universal properties would be impractical due to the complicated coherence conditions ... More
Automated Calibration System for a High-Precision Measurement of Neutrino Mixing Angle $θ_{13}$ with the Daya Bay Antineutrino DetectorsMay 10 2013We describe the automated calibration system for the antineutrino detectors in the Daya Bay Neutrino Experiment. This system consists of 24 identical units instrumented on 8 identical 20-ton liquid scintillator detectors. Each unit is a fully automated ... More
X-ray exploration of the outskirts of the nearby Centaurus cluster using Suzaku and ChandraMar 18 2013We present Suzaku observations of the Centaurus cluster out to 0.95r200, taken along a strip to the north west. We have also used congruent Chandra observations of the outskirts to resolve point sources down to a threshold flux around 7 times lower than ... More
On Nonlocal Parabolic Steady-State Equations of Cooperative or Competing SystemsAug 18 2010Some systems of parabolic equations with nonlocal initial conditions are studied. The systems arise when considering steady-state solutions to diffusive age-structured cooperative or competing species. Local and global bifurcation techniques are employed ... More
Distributive laws via admissibilityJun 29 2017May 04 2018This paper concerns the problem of lifting a KZ doctrine P to the 2-category of pseudo T-algebras for some pseudomonad T. Here we show that this problem is equivalent to giving a pseudo-distributive law (meaning that the lifted pseudomonad is automatically ... More
Stable immersions in orbifoldsDec 10 2013Aug 21 2014We prove that in any hyperbolic orbifold with one boundary component, the product of any hyperbolic fundamental group element with a sufficiently large multiple of the boundary is represented by a geodesic loop that virtually bounds an immersed surface. ... More
Coexistence Steady States in a Predator-Prey ModelFeb 09 2010An age-structured predator-prey system with diffusion and Holling-Tanner-type nonlinearities is considered. Regarding the intensity of the fertility of the predator as bifurcation parameter, we prove that a branch of positive coexistence steady states ... More
Coefficient growth in square chainsFeb 27 2019Suppose $((\cdots((x^{2}-c_{1})^{2}-c_{2})^{2}\cdots)^{2}-c_{k-1})^{2}-c_{k}$ splits into linear factors over $\mathbb{Z}$ and $c_{k}\neq0$. We show that for each $j$ and each prime $p$, if $p\leq2^{j-1}$ then $p$ divides $c_{j}$. Consequently, $$\ln ... More
New approaches to Bayesian consistencyMar 29 2005We use martingales to study Bayesian consistency. We derive sufficient conditions for both Hellinger and Kullback-Leibler consistency, which do not rely on the use of a sieve. Alternative sufficient conditions for Hellinger consistency are also found ... More
Generic bicategoriesMay 04 2018It is well known that to give an oplax functor of bicategories $\mathbf{1}\to\mathscr{C}$ is to give a comonad in $\mathscr{C}$. Here we generalize this fact, replacing the terminal bicategory by any bicategory $\mathscr{A}$ for which the composition ... More
Systematic derivation of a surface polarization model for planar perovskite solar cellsAug 30 2017Increasing evidence suggests that the presence of mobile ions in perovskite solar cells can cause a current-voltage curve hysteresis. Steady state and transient current-voltage characteristics of a planar metal halide CH$_3$NH$_3$PbI$_3$ perovskite solar ... More
R$^3$SGM: Real-time Raster-Respecting Semi-Global Matching for Power-Constrained SystemsOct 30 2018Stereo depth estimation is used for many computer vision applications. Though many popular methods strive solely for depth quality, for real-time mobile applications (e.g. prosthetic glasses or micro-UAVs), speed and power efficiency are equally, if not ... More
Effects of the variability of the nucleus of NGC1275 on X-ray observations of the surrounding intracluster mediumMay 14 2015The active galaxy NGC1275 lies at the centre of the Perseus cluster of galaxies, which is the X-ray brightest cluster in the Sky. The nucleus shows large variability over the past few decades. We compile a lightcurve of its X-ray emission covering about ... More
Observation of coherent Josephson response in the non-linear ab-plane microwave impedance of $YBa_{2}Cu_{3}O_{6.95}$ single crystalsAug 05 1997We report novel non-linear phenomena in the $ab$-plane microwave impedance of $YBaCu_{2}O_{7-\delta }$ single crystals. The $R_s$ vs. $H_{rf}$ data are well described by the non-linear RSJ model : $\dot{\phi}+\sin \phi =i_{rf}\cos \omega t$. The entire ... More
New features in the microwave response of YBCO crystals: Evidence for a multi-component order parameterOct 05 1996Apr 24 1997New features are reported in precision measurements of the complex microwave conductivity of high quality $YBa_{2}Cu_{3}O_{6.95}$ crystals grown in $BaZrO_{3}$ crucibles. A third peak in the normal conductivity, $\sigma_{1}(T)$, at around $80K$, and enhanced ... More
Controlling Personality-Based Stylistic Variation with Neural Natural Language GeneratorsMay 22 2018Natural language generators for task-oriented dialogue must effectively realize system dialogue actions and their associated semantics. In many applications, it is also desirable for generators to control the style of an utterance. To date, work on task-oriented ... More
Iterated Monodromy Groups of Intermediate GrowthAug 05 2012Aug 29 2013We give two new examples of groups of intermediate growth, by a method that was first used by Bux and P\'erez. Our examples are the groups generated by the automata with the kneading sequences 11(0) and 0(011). By results of Nekrashevych, both of these ... More
Measuring the Edwards-Anderson order parameter of the Bose glass: a quantum gas microscope approachJul 18 2016Oct 24 2016With the advent of spatially resolved fluorescence imaging in quantum gas microscopes, it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using ... More
Predictive Embeddings for Hate Speech Detection on TwitterSep 27 2018We present a neural-network based approach to classifying online hate speech in general, as well as racist and sexist speech in particular. Using pre-trained word embeddings and max/mean pooling from simple, fully-connected transformations of these embeddings, ... More
Using Natural Language Processing and Qualitative Analysis to Intervene in Gang Violence: A Collaboration Between Social Work Researchers and Data ScientistsSep 28 2016The U.S. has the highest rate of firearm-related deaths when compared to other industrialized countries. Violence particularly affects low-income, urban neighborhoods in cities like Chicago, which saw a 40% increase in firearm violence from 2014 to 2015 ... More
Generalized unitarity and the worldsheet S matrix in AdS_n x S^n x M^(10-2n)Apr 15 2013May 27 2014The integrability-based solution of string theories related to AdS(n)/CFT(n-1) dualities relies on the worldsheet S matrix. Using generalized unitarity we construct the terms with logarithmic dependence on external momenta at one- and two-loop order in ... More
On the magnetic structure of Sr3Ir2O7: an x-ray resonant scattering studyJul 01 2012This report presents azimuthal dependent and polarisation dependent x-ray resonant magnetic scattering at the Ir L3 edge for the bilayered iridate compound, Sr3Ir2O7. Two magnetic wave vectors, k1=(1/2,1/2,0) and k2=(1/2,-1/2,0), result in domains of ... More
The Role of Feedback in Shaping the Structure of the Interstellar MediumMar 03 2014We present an analysis of the role of feedback in shaping the neutral hydrogen (HI) content of simulated disc galaxies. For our analysis, we have used two realisations of two separate Milky Way-like (~L*) discs - one employing a conservative feedback ... More
The X-ray coronae of the two brightest galaxies in the Coma clusterJan 14 2014We use deep Chandra X-ray Observatory observations to examine the coronae of the two brightest cluster galaxies in the Coma cluster of galaxies, NGC 4874 and NGC 4889. We find that NGC 4889 hosts a central depression in X-ray surface brightness consistent ... More
Linear Structures in the Core of the Coma Cluster of GalaxiesSep 19 2013The hot X-ray emitting plasma in galaxy clusters is predicted to have turbulent motions which can contribute around ten percent of the cluster's central energy density. We report deep Chandra X-ray Observatory observations of the Coma cluster core, showing ... More
Measurement of the Proton's Neutral Weak Magnetic Form FactorFeb 26 1997We report the first measurement of the parity-violating asymmetry in elastic electron scattering from the proton. The asymmetry depends on the neutral weak magnetic form factor of the proton which contains new information on the contribution of strange ... More
Thirty Meter Telescope Site Testing I: OverviewApr 07 2009As part of the conceptual and preliminary design processes of the Thirty Meter Telescope (TMT), the TMT site testing team has spent the last five years measuring the atmospheric properties of five candidate mountains in North and South America with an ... More
Do high redshift quasars have powerful jets?Apr 29 2014Double-lobed radio galaxies a few 100s of kpc in extent, like Cygnus A, are common at redshifts of 1 to 2, arising from some 10 per cent of the most powerful Active Galactic Nuclei (AGN). At higher redshifts they are rare, with none larger than a few ... More
Determination of the Antiferroquadrupolar Order Parameters in UPd3Oct 26 2006By combining accurate heat capacity and X-ray resonant scattering results we have resolved the long standing question regarding the nature of the quadrupolar ordered phases in UPd_3. The order parameter of the highest temperature quadrupolar phase has ... More
Spin dynamics of coupled spin ladders near quantum criticality in Ba2CuTeO6Jun 11 2018Dec 07 2018We report inelastic neutron scattering measurements of the magnetic excitations in Ba2CuTeO6, proposed by ab initio calculations to magnetically realize weakly coupled antiferromagnetic two-leg spin-1/2 ladders. Isolated ladders are expected to have a ... More
The role of mutation rate variation and genetic diversity in the architecture of human diseaseAug 29 2013We have investigated the role that the mutation rate and the structure of genetic variation at a locus play in determining whether a gene is involved in disease. We predict that the mutation rate and its genetic diversity should be higher in genes associated ... More
Parity-Violating Electron Scattering and the Electric and Magnetic Strange Form Factors of the NucleonJul 22 2012Measurement of the neutral weak vector form factors of the nucleon provides unique access to the strange quark content of the nucleon. These form factors can be studied using parity-violating electron scattering. A comprehensive program of experiments ... More
Caenorhabditis elegans and the network control framework - FAQsMay 28 2018Control is essential to the functioning of any neural system. Indeed, under healthy conditions the brain must be able to continuously maintain a tight functional control between the system's inputs and outputs. One may therefore hypothesise that the brain's ... More
Fractal and Multifractal Properties of Electrographic Recordings of Human Brain Activity: Toward Its Use as a Signal Feature for Machine Learning in Clinical ApplicationsJun 11 2018Dec 11 2018The brain is a system operating on multiple time scales, and characterisation of dynamics across time scales remains a challenge. One framework to study such dynamics is that of fractal geometry. However, currently there exists no established method for ... More
The Effect of Resource Limits and Task Complexity on Collaborative Planning in DialogueNov 15 1995This paper shows how agents' choice in communicative action can be designed to mitigate the effect of their resource limits in the context of particular features of a collaborative planning task. I first motivate a number of hypotheses about effective ... More
Redundancy in Collaborative DialogueMar 16 1995In dialogues in which both agents are autonomous, each agent deliberates whether to accept or reject the contributions of the current speaker. A speaker cannot simply assume that a proposal or an assertion will be accepted. However, an examination of ... More
Experimentally Evaluating Communicative Strategies: The Effect of the TaskAug 24 1994Effective problem solving among multiple agents requires a better understanding of the role of communication in collaboration. In this paper we show that there are communicative strategies that greatly improve the performance of resource-bounded agents, ... More
Luminous "Dark" HalosAug 10 1999Aug 07 2000Several lines of evidence suggest that cold, dense gas clouds make a substantial contribution to the total mass of dark halos. If so then physical collisions between clouds must occur; these cause strong, radiative shocks to propagate through the cold ... More
Dark Matter in the Milky Way's Dwarf Spheroidal SatellitesMay 02 2012The Milky Way's dwarf spheroidal satellites include the nearest, smallest and least luminous galaxies known. They also exhibit the largest discrepancies between dynamical and luminous masses. This article reviews the development of empirical constraints ... More
Theory of Tunneling for Rough JunctionsMar 01 1999A formally exact expression for the tunneling current, for its separation into specular and diffuse components, and for its directionality, is given for a thick tunnel junction with rough interfaces in terms of the properties of appropriately defined ... More
Orthorhombically Mixed s and d$_{x^2-y^2}$ Wave Superconductivity and Josephson TunnelingOct 03 1995The effect of orthorhombicity on Josephson tunneling in high T$_c$ superconductors such as YBCO is studied for both single crystals and highly twinned crystals. It is shown that experiments on highly twinned crystals experimentally determine the symmetry ... More
On the Mathematics of the Jeffreys-Lindley ParadoxMar 13 2015This paper is concerned with the well known Jeffreys-Lindley paradox. In a Bayesian set up, the so-called paradox arises when a point null hypothesis is tested and an objective prior is sought for the alternative hypothesis. In particular, the posterior ... More
A generalization of the Gaussian formula and a q-analog of Fleck's congruenceFeb 01 2012The q-binomial coefficients are the polynomial cousins of the traditional binomial coefficients, and a number of identities for binomial coefficients can be translated into this polynomial setting. For instance, the familiar vanishing of the alternating ... More
Even-integer continued fractions and the Farey treeAug 06 2015Singerman introduced to the theory of maps on surfaces an object that is a universal cover for any map. This object is a tessellation of the hyperbolic plane together with a certain subset of the ideal boundary. The 1-skeleton of this tessellation comprises ... More
Geodesic Rosen continued fractionsOct 06 2013Apr 21 2015We describe how to represent Rosen continued fractions by paths in a class of graphs that arise naturally in hyperbolic geometry. This representation gives insight into Rosen's original work about words in Hecke groups, and it also helps us to identify ... More
Observation of out-of-plane spin texture in a SrTiO3 (111) two-dimensional electron gasJun 05 2018We explore the second order bilinear magnetoelectric resistance (BMER) effect in the d-electron-based two-dimensional electron gas (2DEG) at the SrTiO3 (111) surface. We find an evidence of a spin-split band structure with the archetypal spin-momentum ... More
In-situ strain-tuning of the metal-insulator-transition of Ca$_{2}$RuO$_{4}$ in angle-resolved photoemission experimentsMar 01 2018Oct 24 2018We report the evolution of the $k$-space electronic structure of lightly doped bulk Ca$_{2}$RuO$_{4}$ with uniaxial strain. Using ultrathin plate-like crystals, we achieve strain levels up to $-4.1\%$, sufficient to suppress the Mott phase and access ... More
Extreme Scattering Events: insights into the interstellar medium on AU-scalesOct 25 2006Several radio-wave scintillation phenomena exhibit properties which are difficult to accommodate within the standard propagation model based on distributed Kolmogorov turbulence in the ionised ISM; here we discuss one such phenomenon, namely Extreme Scattering ... More
Supersymmetry and Chiral SymmetryDec 14 1999We dispute a recent claim for a nonperturbative nonrenormalisation theorem stating that mass cannot be spontaneously generated in supersymmetric QED. We also extend a long-standing perturbative result, namely that the effective potential is zero to all ... More
Extreme scattering of pulsarsNov 07 1999Extreme Scattering Events are radio-wave lensing events caused by AU-sized concentrations of ionised gas. Although they were discovered more than a decade ago we still have no clear picture of the physical nature of the lenses. To discriminate between ... More
Inferring Acceptance and Rejection in Dialogue by Default Rules of InferenceSep 07 1996This paper discusses the processes by which conversants in a dialogue can infer whether their assertions and proposals have been accepted or rejected by their conversational partners. It expands on previous work by showing that logical consistency is ... More
Extreme points in limit setsNov 16 2018Given an iterated function system of affine dilations with fixed points the vertices of a regular polygon, we characterize which points in the limit set lie on the boundary of its convex hull.
Origins of Life: A Problem for PhysicsMay 23 2017The origins of life stands among the great open scientific questions of our time. While a number of proposals exist for possible starting points in the pathway from non-living to living matter, these have so far not achieved states of complexity that ... More
The Descent of MathMay 02 2015Nov 09 2015A perplexing problem in understanding physical reality is why the universe seems comprehensible, and correspondingly why there should exist physical systems capable of comprehending it. In this essay I explore the possibility that rather than being an ... More
Uniform Symbolic Topologies in Normal Toric RingsJun 20 2017Oct 03 2017Given a normal toric algebra $R$, we compute a uniform integer $D = D(R) > 0$ such that the symbolic power $P^{(D N)} \subseteq P^N$ for all $N >0$ and all monomial primes $P$. We compute the multiplier $D$ explicitly in terms of the polyhedral cone data ... More
Rational Singularities and Uniform Symbolic TopologiesOct 10 2015Oct 03 2017Take $(R, \mathfrak{m})$ any normal Noetherian domain, either local or $\mathbb{N}$-graded over a field. We study the question of when $R$ satisfies the uniform symbolic topology property (USTP) of Huneke, Katz, and Validashti: namely, that there exists ... More
A note on Non-Noetherian Cohen-Macaulay ringsDec 12 2018Jan 10 2019In this note, we study the Cohen-Macaulayness of non-Noetherian rings. We show that Hochster's celebrated theorem that a finitely generated normal semigroup ring is Cohen-Macaulay does not extend to non-Noetherian rings. We also show that for any valuation ... More
Structured Topological Field Theories via Crossed Simplicial GroupsMar 08 2016We show how the framework of crossed simplicial groups may be used to provide a classification of topological field theories on open cobordism categories defined by reductions of the structure group to a planar Lie group. Such theories are equivalent ... More
The BBN ManifestoSep 18 1996In this manifesto I review the status of standard BBN in light of recent observational data (e.g., QSO deuterium and Izotov etal. helium-4).
On The Correct Thermo-dynamic Potential for Electro-static Dielectric EnergyMar 03 2018Various types of equilibrium processes involve electric fields. In some cases, the electrical energy appears to be negative (e.g. if the voltage is fixed by an external source). This paper explains how to derive the correct thermo-dynamic potential for ... More
On a three-dimensional free boundary problem modeling electrostatic memsJun 01 2015We consider the dynamics of an electrostatically actuated thin elastic plate being clamped at its boundary above a rigid plate. The model includes the harmonic electrostatic potential in the three-dimensional time-varying region between the plates along ... More
A variational approach to a stationary free boundary problem modeling MEMSSep 09 2014A variational approach is employed to find stationary solutions to a free boundary problem modeling an idealized electrostatically actuated MEMS device made of an elastic plate coated with a thin dielectric film and suspended above a rigid ground plate. ... More
A free boundary problem modeling electrostatic MEMS: I. Linear bending effectsAug 28 2013The dynamical and stationary behaviors of a fourth-order evolution equation with clamped boundary conditions and a singular nonlocal reaction term, which is coupled to an elliptic free boundary problem on a non-smooth domain, are investigated. The equation ... More