Results for "Robert Hager"

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The nonlinear dispersion relation of geodesic acoustic modesSep 15 2011The energy input and frequency shift of geodesic acoustic modes (GAMs) due to turbulence in tokamak edge plasmas are investigated in numerical two-fluid turbulence studies. Surprisingly, the turbulent GAM dispersion relation is qualitatively equivalent ... More
Learning in an Uncertain World: Representing Ambiguity Through Multiple HypothesesDec 01 2016Aug 22 2017Many prediction tasks contain uncertainty. In some cases, uncertainty is inherent in the task itself. In future prediction, for example, many distinct outcomes are equally valid. In other cases, uncertainty arises from the way data is labeled. For example, ... More
Radial propagation of geodesic acoustic modesApr 24 2009Oct 21 2009The GAM group velocity is estimated from the ratio of the radial free energy flux to the total free energy applying gyrokinetic and two-fluid theory. This method is much more robust than approaches that calculate the group velocity directly and can be ... More
Automated Surgical Activity Recognition with One Labeled SequenceJul 20 2019Prior work has demonstrated the feasibility of automated activity recognition in robot-assisted surgery from motion data. However, these efforts have assumed the availability of a large number of densely-annotated sequences, which must be provided manually ... More
Recognizing Surgical Activities with Recurrent Neural NetworksJun 20 2016Jun 22 2016We apply recurrent neural networks to the task of recognizing surgical activities from robot kinematics. Prior work in this area focuses on recognizing short, low-level activities, or gestures, and has been based on variants of hidden Markov models and ... More
An ellipsoidal branch and bound algorithm for global optimizationDec 09 2009A branch and bound algorithm is developed for global optimization. Branching in the algorithm is accomplished by subdividing the feasible set using ellipses. Lower bounds are obtained by replacing the concave part of the objective function by an affine ... More
An exact algorithm for graph partitioningDec 09 2009An exact algorithm is presented for solving edge weighted graph partitioning problems. The algorithm is based on a branch and bound method applied to a continuous quadratic programming formulation of the problem. Lower bounds are obtained by decomposing ... More
Moment Preserving Constrained Resampling with Applications to Particle-in-Cell MethodsFeb 17 2017Oct 22 2017In simulations of partial differential equations using particle-in-cell (PIC) methods, it is often advantageous to resample the particle distribution function to increase simulation accuracy, reduce compute cost, and/or avoid numerical instabilities. ... More
Collecting and Presenting Reproducible Intranode Stencil Performance: INSPECTJun 19 2019Jul 02 2019Stencil algorithms have been receiving considerable interest in HPC research for decades. The techniques used to approach multi-core stencil performance modeling and engineering span basic runtime measurements, elaborate performance models, detailed hardware ... More
Verification of long wavelength electromagnetic modes with a gyrokinetic-fluid hybrid model in the XGC codeFeb 16 2017As an alternative option to kinetic electrons, the gyrokinetic total-f particle-in-cell (PIC) code XGC1 has been extended to the MHD/fluid type electromagnetic regime by combining gyrokinetic PIC ions with massless drift-fluid electrons analogous to Chen ... More
Optimizing ccNUMA locality for task-parallel execution under OpenMP and TBB on multicore-based systemsDec 30 2010Task parallelism as employed by the OpenMP task construct or some Intel Threading Building Blocks (TBB) components, although ideal for tackling irregular problems or typical producer/consumer schemes, bears some potential for performance bottlenecks if ... More
VolMap: A Real-time Model for Semantic Segmentation of a LiDAR surrounding viewJun 12 2019This paper introduces VolMap, a real-time approach for the semantic segmentation of a 3D LiDAR surrounding view system in autonomous vehicles. We designed an optimized deep convolution neural network that can accurately segment the point cloud produced ... More
A Proof of Concept for Optimizing Task Parallelism by Locality QueuesFeb 11 2009Task parallelism as employed by the OpenMP task construct, although ideal for tackling irregular problems or typical producer/consumer schemes, bears some potential for performance bottlenecks if locality of data access is important, which is typically ... More
Toward a Science of Autonomy for Physical Science: HealthcareSep 19 2016In Star Wars Episode V, we see Luke Skywalker being repaired by a surgical robot. In the context of the movie, this doesn't seem surprising or disturbing. After all, it is a long, long time ago, in a galaxy far, far away. It would never happen here. Or ... More
Estimation Procedures for Robust Sensor ControlMar 27 2013Many robotic sensor estimation problems can characterized in terms of nonlinear measurement systems. These systems are contaminated with noise and may be underdetermined from a single observation. In order to get reliable estimation results, the system ... More
Semantic Stereo for Incidental Satellite ImagesNov 21 2018The increasingly common use of incidental satellite images for stereo reconstruction versus rigidly tasked binocular or trinocular coincident collection is helping to enable timely global-scale 3D mapping; however, reliable stereo correspondence from ... More
Unitarity in the Schroedinger Formalism of QFT in Curved Space-TimeJan 21 2019Jan 23 2019We review the general quantization of scalar fields in curved space-times and discuss the determination of the ground-state. We give an argument for the instability of the ground-state of a QFT in a semi-classical space-time of Bianchi-type I, by explicitly ... More
The moduli space of complex two dimensional associative algebrasMar 28 2009In this paper, we study moduli spaces of 2-dimensional complex associative algebras. We give a complete calculation of the cohomology of every element in the moduli space, as well as compute their versal deformations.
The moduli space of $1|1$-dimensional complex associative algebrasMar 28 2009In this paper, we study the moduli space of $1|1$-dimensional complex associative algebras. We give a complete calculation of the cohomology of every element in the moduli space, as well as compute their versal deformations.
Introducing a Performance Model for Bandwidth-Limited Loop KernelsMay 06 2009We present a performance model for bandwidth limited loop kernels which is founded on the analysis of modern cache based microarchitectures. This model allows an accurate performance prediction and evaluation for existing instruction codes. It provides ... More
Eigenvalue asymptotics for randomly perturbed non-selfadjoint operatorsJan 16 2006May 04 2007We consider quite general $h$-pseudodifferential operators on $R^n$ with small random perturbations and show that in the limit of small $h$ the eigenvalues are distributed according to a Weyl law with a probabality that tends to 1. The first author has ... More
Event-Based Transverse Momentum ResummationApr 17 2019We have developed a framework for automated transverse momentum resummation for arbitrary electroweak final states based on reweighting tree-level events. It is fully differential in the kinematics of the electroweak final states, which facilitates a ... More
Verification of the global gyrokinetic stellarator code XGC-S for linear ion temperature gradient driven modesMay 14 2019XGC (X-point Gyrokinetic Code) is a whole-volume, total-f gyrokinetic particle-in-cell code developed for modelling tokamaks. In recent work, XGC has been extended to model more general 3D toroidal magnetic configurations, such as stellarators. These ... More
2D Crystal Shapes, Droplet Condensation and Exponential Slowing Down in Simulations of First-Order Phase TransitionsJan 18 2002Apr 14 2003Multicanonical ensemble simulations for the simulation of first-order phase transitions suffer from exponential slowing down. Monte Carlo autocorrelation times diverge exponentially with free energy barriers $\Delta F$, which in $L^d$ boxes grow as $L^{d-1}$. ... More
Choice of the uncritical manifold for dilute polymer solutionsDec 21 2004We discuss the dependence of the results of renormalized perturbation theory for dilute polymer solutions on the choice of the uncritical manifold where the perturbation series are evaluated. Special emphasis is given to the influence of polydispersity ... More
Theta-point behavior of diluted polymer solutions: Can one observe the universal logarithmic corrections predicted by field theory?Aug 31 1999In recent large scale Monte-Carlo simulations of various models of Theta-point polymers in three dimensions Grassberger and Hegger found logarithmic corrections to mean field theory with amplitudes much larger than the universal amplitudes of the leading ... More
Projection algorithms for non-convex minimization, with application to sparse principal component analysisApr 16 2014Mar 30 2015We consider concave minimization problems over non-convex sets.Optimization problems with this structure arise in sparse principal component analysis. We analyze both a gradient projection algorithm and an approximate Newton algorithm where the Hessian ... More
An Active Set Algorithm for Nonlinear Optimization with Polyhedral ConstraintsJun 07 2016A polyhedral active set algorithm PASA is developed for solving a nonlinear optimization problem whose feasible set is a polyhedron. Phase one of the algorithm is the gradient projection method, while phase two is any algorithm for solving a linearly ... More
Inexact alternating direction multiplier methods for separable convex optimizationApr 08 2016Inexact alternating direction multiplier methods (ADMMs) are developed for solving general separable convex optimization problems with a linear constraint and with an objective that is the sum of smooth and nonsmooth terms. The approach involves linearized ... More
Perturbations of Jordan MatricesDec 06 2006We consider perturbations of a large Jordan matrix, either random and small in norm or of small rank. In both cases we show that most of the eigenvalues of the perturbed matrix are very close to a circle with centre at the origin. In the case of random ... More
Ohmic Losses in Valence-band Photoemission ExperimentsAug 14 2000Photoemission experiments involve the motion of an electron near a conducting surface. This necessarily generates heat by ohmic losses from eddy currents. This inelastic scattering of the electrons will result in a downward shift in observed spectra. ... More
Theory of Percolative Conduction in Polycrystaline High-temperature SuperconductorsNov 17 1998Jul 01 1999Conduction in bulk polycrystalline high-T$_c$ superconductors with relatively high critical currents has been shown to be percolative. This phenomenon is due to weak links at grain boundaries. These weak links are the major limiting factor for technological ... More
The Chern-Simons state for the non-diagonal Bianchi IX modelFeb 03 1998The Bianchi IX mixmaster model is quantized in its non-diagonal form, imposing spatial diffeomorphism, time reparametrization and Lorentz invariance as constraints on physical state vectors before gauge-fixing. The result turns out to be different from ... More
Exact quantum states for the diagonal Bianchi type IX model with negative cosmological constantMay 17 1996Quantum states of the diagonal Bianchi type IX model with negative cosmological constant $\Lambda$ are obtained by transforming the Chern-Simons solution in Ashtekar's variables to the metric representation. We apply our method developed earlier for $\Lambda>0$ ... More
Triad representation of the Chern-Simons state in quantum gravityMar 30 2000We investigate a triad representation of the Chern-Simons state of quantum gravity with a non-vanishing cosmological constant. It is shown that the Chern-Simons state, which is a well-known exact wavefunctional within the Ashtekar theory, can be transformed ... More
Conditions for the importance of inelastic losses in photoemissionDec 04 2001It is shown that for materials near the metal insulator transition, inelastic losses can give rise to substantial changes on a scale of 10-100 meV in the observed lineshape compared to the intrinsic spectral function of an electron photoemitted from a ... More
Effective Lifetimes of $B_s$ Decays and their Constraints on the $B_s^0$-$\bar B_s^0$ Mixing ParametersSep 23 2011Measurements of the effective lifetimes of $B_s$-meson decays, which only require untagged rate analyses, allow us to probe the width difference $\Delta\Gamma_s$ and the CP-violating phase $\phi_s$ of $B^0_s$-$\bar B^0_s$ mixing. We point out that the ... More
A Fresh Look at B_{s,d} -> pi pi, pi K, K K DecaysDec 03 2010Using updated measurements and SU(3)-breaking form factors, we have a detailed look at the B_d -> pi^+ pi^-, B_s -> K^+ K^- and B_d -> pi^\mp K^\pm, B_s -> pi^\pm K^\mp systems. The corresponding decays are related to each other by the U-spin symmetry ... More
A Flow-aware MAC Protocol for a Passive Optical Metropolitan Area NetworkFeb 17 2011The paper introduces an original MAC protocol for a passive optical metropolitan area network using time-domain wavelength interleaved networking (TWIN)% as proposed recently by Bell Labs . Optical channels are shared under the distributed control of ... More
An Expectation Maximization Framework for Yule-Simon Preferential Attachment ModelsOct 23 2017Sep 16 2018In this paper we develop an Expectation Maximization(EM) algorithm to estimate the parameter of a Yule-Simon distribution. The Yule-Simon distribution exhibits the "rich get richer" effect whereby an 80-20 type of rule tends to dominate. These distributions ... More
The orbital and superhump periods of the deeply eclipsing dwarf nova SDSS J150240.98+333423.9May 18 2010During July 2009 we observed the first confirmed superoutburst of the eclipsing dwarf nova SDSS J150240.98+333423.9 using CCD photometry. The outburst amplitude was at least 3.9 magnitudes and it lasted at least 16 days. Superhumps having up to 0.35 peak-to-peak ... More
c-axis Josephson Tunneling in Twinned YBCO CrystalsJul 02 1999Jan 13 2000Josephson tunneling between YBCO and Pb with the current flowing along the c-axis of the YBCO is persumed to come from an s-wave component of the superconductivity of the YBCO. Experiments on multi-twin samples are not entirely consistent with this hypothesis. ... More
Theory of Josephson tunneling along the c-axis of YBCOMar 10 1998The existence of Josephson tunneling has been demonstrated between YBa$_2$Cu$_3$O$_{7-\delta}$ and Pb with the current flowing along the c-axis of YBa$_2$Cu$_3$O$_{7-\delta}$. This is presumed to come from an s-wave component of the superconductivity ... More
Physical states of Bianchi type IX quantum cosmologies described by the Chern-Simons functionalMar 18 1996A class of exact solutions of the Wheeler-DeWitt equation for diagonal Bianchi type IX cosmologies with cosmological constant is derived in the metric representation. This class consists of all the ``topological solutions'' which are associated with the ... More
In Pursuit of New Physics with B^0_s -> K^+K^-Nov 04 2010The B^0_s -> K^+K^- decay is the U-spin partner of B^0_d -> pi^+\pi^- and allows a determination of the angle gamma of the unitarity triangle of the Cabibbo-Kobayashi-Maskawa matrix. Using updated information on the branching ratio and the relevant hadronic ... More
Quantum phase transition in a 1D transport model with boson affected hopping: Luttinger liquid versus charge-density-wave behaviorNov 05 2008Feb 10 2009We solve a very general two-channel fermion-boson model describing charge transport within some background medium by means of a refined pseudo-site density matrix renormalization group (DMRG) technique. Performing a careful finite-size scaling analysis, ... More
Efficient multicore-aware parallelization strategies for iterative stencil computationsApr 10 2010Stencil computations consume a major part of runtime in many scientific simulation codes. As prototypes for this class of algorithms we consider the iterative Jacobi and Gauss-Seidel smoothers and aim at highly efficient parallel implementations for cache-based ... More
Performance limitations for sparse matrix-vector multiplications on current multicore environmentsOct 26 2009The increasing importance of multicore processors calls for a reevaluation of established numerical algorithms in view of their ability to profit from this new hardware concept. In order to optimize the existent algorithms, a detailed knowledge of the ... More
On the accuracy and usefulness of analytic energy models for contemporary multicore processorsMar 05 2018This paper presents refinements to the execution-cache-memory performance model and a previously published power model for multicore processors. The combination of both enables a very accurate prediction of performance and energy consumption of contemporary ... More
Temporal and Physical Reasoning for Perception-Based Robotic ManipulationOct 11 2017Accurate knowledge of object poses is crucial to successful robotic manipulation tasks, and yet most current approaches only work in laboratory settings. Noisy sensors and cluttered scenes interfere with accurate pose recognition, which is problematic ... More
Gradient-based methods for sparse recoveryDec 09 2009The convergence rate is analyzed for the SpaSRA algorithm (Sparse Reconstruction by Separable Approximation) for minimizing a sum $f (\m{x}) + \psi (\m{x})$ where $f$ is smooth and $\psi$ is convex, but possibly nonsmooth. It is shown that if $f$ is convex, ... More
Delay Propagation and Overlapping Mechanisms on Clusters: A Case Study of Idle Periods based on Workload, Communication, and Delay GranularityMay 25 2019Jul 19 2019Analytic, first-principles performance modeling of distributed-memory applications is difficult due to a wide spectrum of random disturbances caused by the application and the system. These disturbances (commonly called "noise") destroy the assumptions ... More
Information and Multi-Sensor CoordinationMar 27 2013The control and integration of distributed, multi-sensor perceptual systems is a complex and challenging problem. The observations or opinions of different sensors are often disparate incomparable and are usually only partial views. Sensor information ... More
Fluctuations of steps on crystal surfacesAug 24 2001Fluctuations of isolated and pairs of ascending steps of monoatomic height are studied in the framework of SOS models, using mainly Monte Carlo techniques. Below the roughening transistion of the surface, the profiles of long steps show the same scaling ... More
Best practices for HPM-assisted performance engineering on modern multicore processorsJun 17 2012Many tools and libraries employ hardware performance monitoring (HPM) on modern processors, and using this data for performance assessment and as a starting point for code optimizations is very popular. However, such data is only useful if it is interpreted ... More
LIKWID: Lightweight Performance ToolsApr 26 2011Jan 07 2013Exploiting the performance of today's microprocessors requires intimate knowledge of the microarchitecture as well as an awareness of the ever-growing complexity in thread and cache topology. LIKWID is a set of command line utilities that addresses four ... More
LIKWID: A lightweight performance-oriented tool suite for x86 multicore environmentsApr 26 2010Jun 30 2010Exploiting the performance of today's processors requires intimate knowledge of the microarchitecture as well as an awareness of the ever-growing complexity in thread and cache topology. LIKWID is a set of command-line utilities that addresses four key ... More
Electron confinement in graphene with gate-defined quantum dotsMar 19 2015Apr 20 2016We theoretically analyse the possibility to electrostatically confine electrons in circular quantum dot arrays, impressed on contacted graphene nanoribbons by top gates. Utilising exact numerical techniques, we compute the scattering efficiency of a single ... More
A Continuous Refinement Strategy for the Multilevel Computation of Vertex SeparatorsNov 22 2013The Vertex Separator Problem (VSP) on a graph is the problem of finding the smallest collection of vertices whose removal separates the graph into two disjoint subsets of roughly equal size. Recently, Hager and Hungerford [1] developed a continuous bilinear ... More
Data access optimizations for highly threaded multi-core CPUs with multiple memory controllersDec 14 2007Jan 28 2008Processor and system architectures that feature multiple memory controllers are prone to show bottlenecks and erratic performance numbers on codes with regular access patterns. Although such effects are well known in the form of cache thrashing and aliasing ... More
A Decentralized Multi-block ADMM for Demand-side Primary Frequency Control using Local Frequency MeasurementsSep 28 2015We consider demand-side primary frequency control in the power grid provided by smart and flexible loads: loads change consumption to match generation and help the grid while minimizing disutility for consumers incurred by consumption changes. The dual ... More
A Decentralized Multi-block ADMM for Demand-side Primary Frequency Control using Local Frequency MeasurementsSep 28 2015Apr 06 2019We consider demand-side primary frequency control in the power grid provided by smart and flexible loads: loads change consumption to match generation and help the grid while minimizing disutility for consumers incurred by consumption changes. The dual ... More
Delay Propagation and Overlapping Mechanisms on Clusters: A Case Study of Idle Periods based on Workload, Communication, and Delay GranularityMay 25 2019Analytic, first-principles performance modeling of distributed-memory applications is difficult due to a wide spectrum of random disturbances caused by the application and the system. These disturbances (commonly called "noise") destroy the assumptions ... More
Dynamic Template Tracking and RecognitionApr 19 2012In this paper we address the problem of tracking non-rigid objects whose local appearance and motion changes as a function of time. This class of objects includes dynamic textures such as steam, fire, smoke, water, etc., as well as articulated objects ... More
Multicore-aware parallel temporal blocking of stencil codes for shared and distributed memoryDec 22 2009New algorithms and optimization techniques are needed to balance the accelerating trend towards bandwidth-starved multicore chips. It is well known that the performance of stencil codes can be improved by temporal blocking, lessening the pressure on the ... More
Multi-core architectures: Complexities of performance prediction and the impact of cache topologyOct 26 2009The balance metric is a simple approach to estimate the performance of bandwidth-limited loop kernels. However, applying the method to in-cache situations and modern multi-core architectures yields unsatisfactory results. This paper analyzes the in uence ... More
Towards Robot Task Planning From Probabilistic Models of Human SkillsFeb 15 2016We describe an algorithm for motion planning based on expert demonstrations of a skill. In order to teach robots to perform complex object manipulation tasks that can generalize robustly to new environments, we must (1) learn a representation of the effects ... More
A domain-specific language and matrix-free stencil code for investigating electronic properties of Dirac and topological materialsAug 31 2017May 07 2018We introduce PVSC-DTM (Parallel Vectorized Stencil Code for Dirac and Topological Materials), a library and code generator based on a domain-specific language tailored to implement the specific stencil-like algorithms that can describe Dirac and topological ... More
CAS-CNN: A Deep Convolutional Neural Network for Image Compression Artifact SuppressionNov 22 2016Lossy image compression algorithms are pervasively used to reduce the size of images transmitted over the web and recorded on data storage media. However, we pay for their high compression rate with visual artifacts degrading the user experience. Deep ... More
sharpDARTS: Faster and More Accurate Differentiable Architecture SearchMar 23 2019Neural Architecture Search (NAS) has been a source of dramatic improvements in neural network design, with recent results meeting or exceeding the performance of hand-tuned architectures. However, our understanding of how to represent the search space ... More
Phenomenology with a non-zero B_s decay width differenceMay 29 2013The experimentally established non-zero decay width difference of the B_s meson system gives us access to a mass eigenstate rate asymmetry for each B_s transition. This observable is not only the key ingredient in converting between differing definitions ... More
On uniformization of compact Kahler spacesJan 11 2016Jul 29 2016The aim of the note is to extend the uniformization theorem to compact Kahler spaces X with mild singularities and establish a kind of rigidity of their universal coverings. We assume the fundamental group of X is large, residually finite and nonamenable. ... More
Automatic Homeomorphicity of Locally Moving ClonesDec 01 2015Jul 26 2016We extend the work of M. Rubin on locally moving groups to clones, showing that a locally moving polymorphism clone has automatic homeomorphicity with respect to the class of all polymorphism clones. We show that if $\mathrm{Pol}(M,\mathcal{L})$ is the ... More
Theory of Neutron Diffraction from the Vortex Lattice in UPt3Sep 04 1996Neutron scattering experiments have recently been performed in the superconducting state of UPt3 to determine the structure of the vortex lattice. The data show anomalous field dependence of the aspect ratio of the unit cell in the B phase. There is apparently ... More
Theory News on $B_{s(d)} \to μ^+μ^-$ DecaysDec 20 2012The rare decays $B_{s(d)} \to \mu^+\mu^-$ play a key role for the testing of the Standard Model. An overview of the most recent theoretical predictions of the corresponding branching ratios is given, emphasizing that the sizable decay width difference ... More
On Branching Ratios of $B_s$ Decays and the Search for New Physics in $B^0_s\to μ^+μ^-$Aug 14 2012The LHCb experiment has recently established a sizable width difference between the mass eigenstates of the $B_s$-meson system. This phenomenon leads to a subtle difference at the 10% level between the experimental branching ratios of $B_s$ decays extracted ... More
Extracting CKM Phases from Angular Distributions of $B_{d,s}$ Decays into Admixtures of CP EigenstatesMar 31 1999Apr 26 1999The time-dependent angular distributions of certain $B_{d,s}$ decays into final states that are admixtures of CP-even and CP-odd configurations provide valuable information about CKM phases and hadronic parameters. We present the general formalism to ... More
CP Violation in B Decays and Strategies for Extracting CKM PhasesSep 01 1998A brief review of CP violation in the $B$-meson system and of strategies to determine the angles $\alpha$, $\beta$ and $\gamma$ of the unitarity triangle of the CKM matrix is given. Both general aspects and some recent developments are discussed, including ... More
B Physics in the LHC Era: Selected TopicsOct 04 2010We have just entered a new round in the testing of the flavour sector of the Standard Model through high-precision measurements of B-meson decays. A particularly exciting aspect is the exploration of the B_s-meson system at LHCb. We focus on two particularly ... More
Controlling Rescattering Effects in Constraints on the CKM Angle $γ$ arising from $B\toπK$ DecaysApr 17 1998It has recently been pointed out that the observables of the decay $B^+\to K^+\bar{K^0}$ and its charge conjugate allow us to take into account rescattering effects in constraints on the CKM angle $\gamma$ arising from $B^\pm\to\pi^\pm K$ and $B_d\to\pi^\pm ... More
Strategies for Fixing the CKM-angle $γ$ and Obtaining Experimental Insights into the World of Electroweak PenguinsSep 01 1995Using the $SU(3)$ flavour symmetry of strong interactions, we propose strategies for extracting both the CKM-angle $\gamma$ and the $\bar b\to\bar uu\bar s$ tree-level amplitude $T'$. We present also an approximate approach using the branching ratios ... More
Electrical Structure of Biological Cells and Tissues: impedance spectroscopy, stereology, and singular perturbation theoryNov 04 2015Impedance Spectroscopy resolves electrical properties into uncorrelated variables, as a function of frequency, with exquisite resolution. Separation is robust and most useful when the system is linear. Impedance spectroscopy combined with appropriate ... More
A note comprising a negative resolution of the Efficient Market HypothesisNov 01 2010This note comprises a negative resolution of the Efficient Market Hypothesis.
On computable approximations of Landau's constantSep 25 2012Nov 18 2012We present an algorithm which computes the Landau constant up to any given precision.
Configuration spaces and braid groups on graphs in roboticsMay 05 1999Configuration spaces of distinct labeled points on the plane are of practical relevance in designing safe control schemes for Automated Guided Vehicles (robots) in industrial settings. In this announcement, we consider the problem of the construction ... More
Novae Ejecta as Discrete Adiabatically Expanding GlobulesJun 26 2013Available data for novae show that the X-ray and visible spectral regions correlate with each other as they evolve. Large differences in ionization exist simultaneously in the two wavelength regimes, and a straightforward model is proposed that explains ... More
Third Parameter Classification of Transients and Novae Ejecta as Ballistically Ejected GlobulesJan 03 2016Feb 03 2016A third parameter, in addition to luminosity and rate of brightness decline, derived from the spectra of transients is suggested as a means of more accurately classifying objects in outburst. Principal component analysis of the spectra of transients is ... More
Cohomological framework for contextual quantum computationsFeb 12 2016Mar 31 2016We present a cohomological formulation of measurement-based quantum computation (MBQC), employing the notion of a phase function. The phase function describes symmetries of the resource state of the MBQC, specifies the computational output, and acts as ... More
Two-dimensional quantum Yang-Mills theory with cornersAug 30 2006Jul 17 2007The solution of quantum Yang-Mills theory on arbitrary compact two-manifolds is well known. We bring this solution into a TQFT-like form and extend it to include corners. Our formulation is based on an axiomatic system that we hope is flexible enough ... More
States on timelike hypersurfaces in quantum field theoryMay 31 2005We investigate the possibility of defining states on timelike hypersurfaces in quantum field theory. To this end we consider hyperplanes in the real massive Klein-Gordon theory using the Schroedinger representation. We find a well defined vacuum wave ... More
Schroedinger's cat and the clock: Lessons for quantum gravityJun 02 2003Oct 15 2003I review basic principles of the quantum mechanical measurement process in view of their implications for a quantum theory of general relativity. It turns out that a clock as an external classical device associated with the observer plays an essential ... More
Probabilities in the general boundary formulationDec 09 2006Aug 03 2012We give an introductory account of the general boundary formulation of quantum theory. We refine its probability interpretation and emphasize a conceptual and historical perspective. We give motivations from quantum gravity and illustrate them with a ... More
The Quantum Geometry of Supersymmetry and the Generalized Group Extension ProblemJun 14 2001May 08 2002We examine the notion of symmetry in quantum field theory from a fundamental representation theoretic point of view. This leads us to a generalization expressed in terms of quantum groups and braided categories. It also unifies the conventional concept ... More
Using Neighborhood Diversity to Solve Hard ProblemsJan 15 2012Jan 17 2012Parameterized algorithms are a very useful tool for dealing with NP-hard problems on graphs. Yet, to properly utilize parameterized algorithms it is necessary to choose the right parameter based on the type of problem and properties of the target graph ... More
Generalized Scheme Transformations for the Elimination of Higher-Loop Terms in the Beta Function of a Gauge TheoryMay 23 2014We construct and study a generalized one-parameter class of scheme transformations, denoted $S_{R,m,k_1}$ with $m \ge 2$, with the property that an $S_{R,m,k_1}$ scheme transformation eliminates the $\ell$-loop terms in the beta function of a gauge theory ... More
Higher-Loop Calculations of the Ultraviolet to Infrared Evolution of a Vectorial Gauge Theory in the Limit $N_c \to \infty$, $N_f \to \infty$ with $N_f/N_c$ FixedFeb 21 2013We consider an asymptotically free vectorial SU($N_c$) gauge theory with $N_f$ fermions in the fundamental representation and analyze higher-loop contributions to the evolution of the theory from the ultraviolet to the infrared in the limit where $N_c ... More
Higher-Loop Structural Properties of the $β$ Function in Asymptotically Free Vectorial Gauge TheoriesJan 15 2013We investigate some higher-loop structural properties of the $\beta$ function in asymptotically free vectorial gauge theories. Our main focus is on theories with fermion contents that lead to an infrared (IR) zero in $\beta$. We present analytic and numerical ... More
Variants of the Standard Model with Electroweak-Singlet QuarksAug 30 2008The successful description of current data provided by the Standard Model includes fundamental fermions that are color-singlets and electroweak-nonsinglets, but no fermions that are electroweak-singlets and color-nonsinglets. In an effort to understand ... More
Constraints on $N_c$ in Extensions of the Standard ModelApr 26 2007We consider a class of theories involving an extension of the Standard Model gauge group to an {\it a priori} arbitrary number of colors, $N_c$, and derive constraints on $N_c$. One motivation for this is the string theory landscape. For two natural classes ... More
Exact Potts Model Partition Functions on Ladder GraphsJan 26 2000We present exact calculations of the partition function $Z$ of the $q$-state Potts model and its generalization to real $q$, the random cluster model, for arbitrary temperature on $n$-vertex ladder graphs with free, cyclic, and M\"obius longitudinal boundary ... More