Results for "Griffin Foster"

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Verifying and Reporting Fast Radio BurstsAug 23 2018Fast Radio Bursts (FRBs) are a class of short-duration transients at radio wavelengths with inferred astrophysical origin. The prototypical FRB is a broadband signal that occurs over the extent of the receiver frequency range, is narrow in time, and is ... More
Theory of excitations of the condensate and non-condensate at finite temperaturesJan 18 1999Jan 20 1999We give an overview of the current theory of collective modes in trapped atomic gases at finite temperatures, when the dynamics of the condensate and non-condensate must both be considered. A simple introduction is given to the quantum field formulation ... More
Scalar Field Cosmological Models With Hard Potential WallsJun 29 1998The global behavior of scalar field cosmological models with very hard potential walls is investigated via the simple example of an exponentially steep potential well. It is found that the solutions exhibit a non-trivial oscillatory behavior in the approach ... More
Higher configuration operads by way of quiver GrassmanniansNov 19 2012We introduce a construction that associates, to each finite dimensional k-vector space V, a family of projective k-varieties that comes equipped with the structure of a operad in the category of k-schemes. When dim V = 1, this operad contains, as a suboperad, ... More
Critical behaviour of the bond-interacting self-avoiding walkSep 05 2006The phase diagram for the bond-interacting self-avoiding walk is calculated using transfer matrices on finite strips. The model is shown to have a richer phase diagram than the related $\Theta$-point model. In addition to the standard collapse transition, ... More
Current and Nascent SETI InstrumentsSep 06 2011Here we describe our ongoing efforts to develop high-performance and sensitive instrumentation for use in the search for extra-terrestrial intelligence (SETI). These efforts include our recently deployed Search for Extraterrestrial Emissions from Nearby ... More
Associating curves of low genus to infinite nilpotent groups via the zeta functionSep 20 2002It is known from work of du Sautoy and Grunewald in \cite{duSG1} that the zeta functions counting subgroups of finite index in infinite nilpotent groups depend upon the behaviour of some associated system of algebraic varieties on reduction $\modp.$ Further ... More
Diagonal complexes and the integral homology of the automorphism group of a free productNov 28 2010Sep 07 2011The main goal of this paper is a calculation of the integral (co)homology of the group of symmetric automorphisms of a free product. We proceed by giving a geometric interpretation of symmetric automorphisms via a moduli space of certain diagrams, which ... More
High Precision Arithmetic for Scientific ApplicationsSep 21 2013All but a few digital computers used for scientific computations have supported floating-point and digital arithmetic of rather limited numerical precision. The underlying assumptions were that the systems being studied were basically deterministic and ... More
Deep Inelastic Scattering at HERADec 23 1997Results from the H1 and ZEUS experiments at HERA on deep inelastic scattering are reviewed. The data lead to a consistent picture of a steep rise in the F_2 structure function and in the gluon density within the proton. Important new information on the ... More
Human-Machine Symbiosis, 50 Years OnDec 13 2007Licklider advocated in 1960 the construction of computers capable of working symbiotically with humans to address problems not easily addressed by humans working alone. Since that time, many of the advances that he envisioned have been achieved, yet the ... More
The decay of Hopf solitons in the Skyrme modelOct 05 2016It is understood that the Skyrme model has a topologically interesting baryonic excitation which can model nuclei. So far no stable knotted solutions, of the Skyrme model, have been found. Here we investigate the dynamics of Hopf solitons decaying to ... More
Massive HopfionsDec 12 2010The Skyrme-Faddeev model is a (3+1)-dimensional model which has knotted, string-like, soliton solutions. In this paper we investigate a Skyrme-Faddeev model with an SO(3) symmetry breaking potential. We then rescale this model and take the mass to infinity. ... More
Classifying the near-equality of ribbon Schur functionsOct 01 2018We consider the problem of determining when the difference of two ribbon Schur functions is a single Schur function. We prove that this near-equality phenomenon occurs in sixteen infinite families and we conjecture that these are the only possible cases. ... More
Behavior and performance of the deep belief networks on image classificationDec 03 2009We apply deep belief networks of restricted Boltzmann machines to bags of words of sift features obtained from databases of 13 Scenes, 15 Scenes and Caltech 256 and study experimentally their behavior and performance. We find that the final performance ... More
The obstacle problem for subelliptic non-divergence form operators on homogeneous groupsJul 16 2013The main result established in this paper is the existence and uniqueness of strong solutions to the obstacle problem for a class of subelliptic operators in non-divergence form. The operators considered are structured on a set of smooth vector fields ... More
Pruitt's Estimates in Banach SpaceMay 11 2011Pruitt's estimates on the expectation and the distribution of the time taken by a random walk to exit a ball of radius r are extended to the infinite dimensional setting. It is shown that they separate into two pairs of estimates depending on whether ... More
Modelling and computation using NCoRM mixtures for density regressionAug 02 2016Aug 03 2016Normalized compound random measures are flexible nonparametric priors for related distributions. We consider building general nonparametric regression models using normalized compound random measure mixture models. We develop a general approach to the ... More
Game Theoretic Formation of a Centrality Based NetworkSep 18 2012We model the formation of networks as a game where players aspire to maximize their own centrality by increasing the number of other players to which they are path-wise connected, while simultaneously incurring a cost for each added adjacent edge. We ... More
Collective modes and the effect of single-particle excitations in the BCS-BEC crossover region of a trapped Fermi superfluidMar 28 2005We investigate the collective oscillations in the BCS-BEC crossover region of a trapped Fermi superfluid at T=0. We explicitly include the effect of a Feshbach resonance, which leads to a tunable pairing interaction adjusted by the threshold energy of ... More
Temperature-dependent relaxation times in a trapped Bose-condensed gasJul 20 2001Nov 16 2001Explicit expressions for all the transport coefficients have recently been found for a trapped Bose condensed gas at finite temperatures. These transport coefficients are used to define the characteristic relaxation times, which determine the crossover ... More
On p-adic haromonic Maass functionsJul 10 2017Modular and mock modular forms possess many striking $p$-adic properties, as studied by Bringmann, Guerzhoy, Kane, Kent, Ono, and others. Candelori developed a geometric theory of harmonic Maass forms arising from the de Rham cohomology. In the setting ... More
GREENBURST: a commensal fast radio burst search back-end for the Green Bank TelescopeMar 13 2019We describe the design and deployment of GREENBURST, a commensal Fast Radio Burst (FRB) search system at the Green Bank Telescope. GREENBURST uses the dedicated L-band receiver tap to search over the 960$-$1920 MHz frequency range for pulses with dispersion ... More
A Boundary Tilting Persepective on the Phenomenon of Adversarial ExamplesAug 27 2016Deep neural networks have been shown to suffer from a surprising weakness: their classification outputs can be changed by small, non-random perturbations of their inputs. This adversarial example phenomenon has been explained as originating from deep ... More
Genuine onion: Simple, Fast, Flexible, and Cheap Website AuthenticationJun 12 2015Tor is a communications infrastructure widely used for unfettered and anonymous access to Internet websites. Tor is also used to access sites on the .onion virtual domain. The focus of .onion use and discussion has traditionally been on the offering of ... More
Cacti and filtered distributive lawsSep 25 2011Motivated by the second author's construction of a classifying space for the group of pure symmetric automorphisms of a free product, we introduce and study a family of topological operads, the operads of based cacti, defined for every pointed topological ... More
A Problem-Specific Fault-Tolerance Mechanism for Asynchronous, Distributed SystemsMar 12 2000The idle computers on a local area, campus area, or even wide area network represent a significant computational resource---one that is, however, also unreliable, heterogeneous, and opportunistic. This type of resource has been used effectively for embarrassingly ... More
Universality of collapsing two-dimensional self-avoiding trailsJul 15 2009Aug 13 2009Results of a numerically exact transfer matrix calculation for the model of Interacting Self-Avoiding Trails are presented. The results lead to the conclusion that, at the collapse transition, Self-Avoiding Trails are in the same universality class as ... More
The Mass Spectrum of a Static Adjoint ParticleSep 16 1997The bound states of fermions in the adjoint representation are of interest in supersymmetric models. We investigate the energy spectrum of the simplest -- the gluino-gluon bound states -- on several lattices in the quenched approximation. We use a static ... More
Generalised interacting self-avoiding trails on the square lattice: phase diagram and critical behaviourSep 08 2011A generalised model for interacting self-avoiding trails on the square lattice is presented and studied using numerical transfer matrix methods. The model differentiates between on-site double visits corresponding to collisions, and crossings. Rigidity ... More
No Internal Regret via Neighborhood WatchAug 30 2011We present an algorithm which attains O(\sqrt{T}) internal (and thus external) regret for finite games with partial monitoring under the local observability condition. Recently, this condition has been shown by (Bartok, Pal, and Szepesvari, 2011) to imply ... More
Baby Skyrmion chainsApr 24 2009Previous results on multi-charged Baby Skyrmion solutions have pointed to a modular structure, comprised of charge two rings and single charge one Skyrmions, which combine to form higher charged structures. In this paper we present numerical evidence ... More
Effectiveness of nanoinclusions for reducing bipolar effects in thermoelectric materialsApr 11 2019Bipolar carrier transport is often a limiting factor in the thermoelectric efficiency of narrow bandgap materials (such as Bi2Te3 and PbTe) at high temperatures due to the introduction of an additional term to the thermal conductivity and a reduction ... More
Semisimplicity of certain representation categoriesSep 04 2015We exhibit a correspondence between subcategories of modules over an algebra and sub-bimodules of the dual of that algebra. We then prove that the semisimplicity of certain such categories is equivalent to the existence of a Peter-Weyl decomposition of ... More
Helical buckling of Skyrme-Faddeev solitonsFeb 17 2012Solitons in the Skyrme-Faddeev model on R^2xS^1 are shown to undergo buckling transitions as the circumference of the S^1 is varied. These results support a recent conjecture that solitons in this field theory are well-described by a much simpler model ... More
Implementation of a Direct-Imaging and FX Correlator for the BEST-2 ArrayJan 27 2014A new digital backend has been developed for the BEST-2 array at Radiotelescopi di Medicina, INAF-IRA, Italy which allows concurrent operation of an FX correlator, and a direct-imaging correlator and beamformer. This backend serves as a platform for testing ... More
Intrinsic Instrumental Polarization and High-Precision Pulsar TimingJul 24 2015Radio telescopes are used to accurately measure the time of arrival (ToA) of radio pulses in pulsar timing experiments that target mostly millisecond pulsars (MSPs) due to their high rotational stability. This allows for detailed study of MSPs and forms ... More
Non linear difference equations arising from a deformation of the q-Laguerre weightApr 11 2014We study, in this paper, a one parameter deformation of the $q-$Laguerre weight function. An investigation is made on the polynomials orthogonal with respect to such a weight. With the aid of the two compatibility conditions previously obtained in \cite{Chen-Ism} ... More
Unsupervised Machine Learning of Open Source Russian Twitter Data Reveals Global Scope and Operational CharacteristicsOct 02 2018We developed and used a collection of statistical methods (unsupervised machine learning) to extract relevant information from a Twitter supplied data set consisting of alleged Russian trolls who (allegedly) attempted to influence the 2016 US Presidential ... More
Sample path behavior of a Lévy insurance risk process approaching ruin, under the Cramér-Lundberg and convolution equivalent conditionsSep 26 2013Jan 07 2016Recent studies have demonstrated an interesting connection between the asymptotic behavior at ruin of a L\'evy insurance risk process under the Cram\'er-Lundberg and convolution equivalent conditions. For example, the limiting distributions of the overshoot ... More
Staggered fermions and chiral symmetry breaking in transverse lattice regulated QEDJul 24 1992Staggered fermions are constructed for the transverse lattice regularization scheme. The weak perturbation theory of transverse lattice non-compact QED is developed in light-cone gauge, and we argue that for fixed lattice spacing this theory is ultraviolet ... More
Optimal Control Model of Software Quality for Digital VendorsDec 30 2014This paper models a firm's level of effort in mobile software application production as an optimal control problem to maximize market share and profit in a digital marketplace. Through a rumor-spreading system dynamic, a digital goods vendor can capture ... More
Optimal Digital Product Maintenance with a Continuous Revenue StreamDec 30 2014Feb 25 2017We use a control framework to analyze the digital vendor's profit maximization problem. The vendor captures market share by focusing costly effort on post-launch product maintenance, which influences user perception of the product and drives a revenue ... More
Single-particle excitations in a trapped gas of Fermi atoms in the BCS-BEC crossover regionOct 08 2004We investigate the single-particle properties at T=0 of a trapped superfluid gas of Fermi atoms with a Feshbach resonance. A tunable pairing interaction associated with the Feshbach resonance leads to the BCS-BEC crossover, where the character of superfluidity ... More
Hydrodynamic modes and pulse propagation in a cylindrical Bose gas above the Bose-Einstein transitionJun 09 1998We study hydrodynamic oscillations of a cylindrical Bose gas above the Bose-Einstein transition temperature using the hydrodynamic equations derived by Griffin, Wu and Stringari. This extends recent studies of a cylindrical Bose-condensed gas at T=0. ... More
Surface Region of Superfluid Helium as an Inhomogeneous Bose-Condensed GasNov 20 1995We present arguments that the low density surface region of self-bounded superfluid $^4$He systems is an inhomogeneous dilute Bose gas, with almost all of the atoms occupying the same single-particle state at $T = 0$. Numerical evidence for this complete ... More
Fast Radio Burst 121102 Pulse Detection and Periodicity: A Machine Learning ApproachSep 09 2018We report the detection of 72 new pulses from the repeating fast radio burst FRB 121102 in Breakthrough Listen C-band (4-8 GHz) observations at the Green Bank Telescope. The new pulses were found with a convolutional neural network in data taken on August ... More
Usage Policy-based CPU Sharing in VOsNov 12 2004Resource sharing within Grid collaborations usually implies specific sharing mechanisms at participating sites. Challenging policy issues can arise within virtual organizations (VOs) that integrate participants and resources spanning multiple physical ... More
Multifractal nature of the surface local density of states in three-dimensional topological insulators with magnetic and nonmagnetic disorderNov 28 2011Feb 22 2012We compute the multifractal spectra associated to local density of states (LDOS) fluctuations due to weak quenched disorder, for a single Dirac fermion in two spatial dimensions. Our results are relevant to the surfaces of Z_2 topological insulators such ... More
Baby Skyrmions stabilized by vector mesonsJan 23 2009Recent results suggest that multi-Skyrmions stabilized by omega mesons have very similar properties to those stabilized by the Skyrme term. In this paper we present the results of a detailed numerical investigation of a (2+1)-dimensional analogue of this ... More
Noether charges and black hole mechanics in Einstein-aether theorySep 29 2005Dec 09 2005The Noether charge method for defining the Hamiltonian of a diffeomorphism-invariant field theory is applied to "Einstein-aether" theory, in which gravity couples to a dynamical, timelike, unit-norm vector field. Using the method, expressions are obtained ... More
Doping optimization for the power factor of bipolar thermoelectric materialsJan 15 2019Bipolar carrier transport is often a limiting factor in the thermoelectric efficiency of narrow bandgap materials at high temperatures due to the reduction in the Seebeck coefficient and the introduction of an additional term to the thermal conductivity. ... More
Applications of Data Mining to Electronic CommerceOct 02 2000Electronic commerce is emerging as the killer domain for data mining technology. The following are five desiderata for success. Seldom are they they all present in one data mining application. 1. Data with rich descriptions. For example, wide customer ... More
Mission Opportunities for Human Exploration of Nearby Planetary BodiesOct 18 2016We characterize mission profiles for human expeditions to near-Earth asteroids, Venus, and Mars. Near-Earth objects (NEOs) are the closest destinations beyond cis-lunar space and present a compelling target with capabilities already under development ... More
Structure and Dynamics of the Milky Way: The Evolving PictureSep 16 2010Oct 02 2010From the inception of radio astronomy, the study of the Interstellar Medium has been both aided and frustrated by one fact: we are right within it! Our embedded perspective is favourable to observing kinematic and structural details that are likely to ... More
Prospects for Recovering Galaxy Intrinsic Shapes from Projected QuantitiesMay 08 2019The distribution of three dimensional intrinsic galaxy shapes has been a longstanding open question. The difficulty stems from projection effects meaning one must rely on statistical methods applied to galaxy samples to infer intrinsic shape distributions. ... More
Physics of Low-Dimensional Ultracold Bose GasesFeb 03 2013In this work we investigate the unique properties of ultracold Bose gases in one and two dimensions. In two dimensions, we present simulations of the Berezinskii-Kosterlitz-Thouless (BKT) phase transition using the projected Gross-Pitaevskii equation ... More
Surface critical behaviour of the Interacting Self-Avoiding Trail on the square latticeJul 01 2010The surface critical behaviour of the interacting self-avoiding trail is examined using transfer matrix methods coupled with finite-size scaling. Particular attention is paid to the critical exponents at the ordinary and special points along the collapse ... More
Any-gram Kernels for Sentence Classification: A Sentiment Analysis Case StudyDec 19 2017Any-gram kernels are a flexible and efficient way to employ bag-of-n-gram features when learning from textual data. They are also compatible with the use of word embeddings so that word similarities can be accounted for. While the original any-gram kernels ... More
Physical-type correctness in scientific PythonJul 17 2018Aug 03 2018The representation of units and dimensions in informatics systems is barely codified and often ignored. For instance, the major languages used in scientific computing (Fortran, C and Python), have no type for dimension or unit, and so physical quantities ... More
Better Image Segmentation by Exploiting Dense Semantic PredictionsJun 05 2016It is well accepted that image segmentation can benefit from utilizing multilevel cues. The paper focuses on utilizing the FCNN-based dense semantic predictions in the bottom-up image segmentation, arguing to take semantic cues into account from the very ... More
Lasso ANOVA Decompositions for Matrix and Tensor DataMar 24 2017Feb 09 2019Consider the problem of estimating the entries of an unknown mean matrix or tensor given a single noisy realization. In the matrix case, this problem can be addressed by decomposing the mean matrix into a component that is additive in the rows and columns, ... More
Development of a Silicon Tracker for the All-sky Medium Energy Gamma-ray Observatory PrototypeFeb 25 2019The gamma-ray sky from several hundred keV to $\sim$ a hundred MeV has remained largely unexplored due to the challenging nature of detecting gamma rays in this regime. At lower energies, Compton scattering is the dominant interaction process whereas ... More
Coupled Hartree-Fock-Bogoliubov kinetic equations for a trapped Bose gasDec 16 1998Using the Kadanoff-Baym non-equilibrium Green's function formalism, we derive the self-consistent Hartree-Fock-Bogoliubov (HFB) collisionless kinetic equations and the associated equation of motion for the condensate wavefunction for a trapped Bose-condensed ... More
Optimal Weighting of Multi-View Data with Low Dimensional Hidden StatesSep 25 2012Sep 26 2012In Natural Language Processing (NLP) tasks, data often has the following two properties: First, data can be chopped into multi-views which has been successfully used for dimension reduction purposes. For example, in topic classification, every paper can ... More
The statistical mechanics of the two-dimensional hydrogen-bonding self-avoiding walk including solvent effectsOct 28 2007A two-dimensional square-lattice model for the formation of secondary structures in proteins, the hydrogen-bonding model, is extended to include the effects of solvent quality. This is achieved by allowing configuration-dependent nearest-neighbour interactions. ... More
Large scale canonical correlation analysis with iterative least squaresJul 16 2014Dec 30 2014Canonical Correlation Analysis (CCA) is a widely used statistical tool with both well established theory and favorable performance for a wide range of machine learning problems. However, computing CCA for huge datasets can be very slow since it involves ... More
Fast Ridge Regression with Randomized Principal Component Analysis and Gradient DescentMay 15 2014We propose a new two stage algorithm LING for large scale regression problems. LING has the same risk as the well known Ridge Regression under the fixed design setting and can be computed much faster. Our experiments have shown that LING performs well ... More
Dephasing catastrophe in $4 - ε$ dimensions: A possible instability of the ergodic (many-body-delocalized) phaseOct 13 2017May 09 2018In two dimensions (2D), dephasing by a bath cuts off Anderson localization that would otherwise occur at any energy density for fermions with disorder. For an isolated system with short-range interactions, the system can be its own bath, exhibiting diffusive ... More
Drinfeld Orbifold Algebras for Symmetric GroupsNov 01 2016Drinfeld orbifold algebras are a type of deformation of skew group algebras generalizing graded Hecke algebras of interest in representation theory, algebraic combinatorics, and noncommutative geometry. In this article, we classify all Drinfeld orbifold ... More
A Study of RR1 Lightcurve Modulation in OGLE_III Bulge Time-seriesOct 02 2013We report the results of our study of lightcurve modulation in a sample of 493 RR1 variables from the OGLE-III survey of galactic bulge fields. Each object in this list has 1500 or more I-band observations. We compare our findings with earlier studies ... More
Surface critical behaviour of the vertex-interacting self-avoiding walk on the square latticeNov 01 2012The phase diagram and surface critical behaviour of the vertex-interacting self-avoiding walk are examined using transfer matrix methods extended using DMRG and coupled with finite-size scaling. Particular attention is paid to the critical exponents at ... More
A corner transfer matrix renormalisation group investigation of the vertex-interacting self-avoiding walk modelAug 20 2003A recently introduced extension of the Corner Transfer Matrix Renormalisation Group (CTMRG) method useful for the study of self-avoiding walk type models is presented in detail and applied to a class of interacting self-avoiding walks due to Bl\"ote and ... More
Lower Bounds on Mutual InformationAug 04 2010We correct claims about lower bounds on mutual information (MI) between real-valued random variables made in A. Kraskov {\it et al.}, Phys. Rev. E {\bf 69}, 066138 (2004). We show that non-trivial lower bounds on MI in terms of linear correlations depend ... More
The ferro/antiferromagnetic q-state Potts modelJan 22 2002The critical properties of the mixed ferro/antiferromagnetic q-state Potts model on the square lattice are investigated using the numerical transfer matrix technique. The transition temperature is found to be substantially lower than previously found ... More
Two dimensional self-avoiding walk with hydrogen-like bonding: Phase diagram and critical behaviourOct 10 2001The phase diagram for a two-dimensional self-avoiding walk model on the square lattice incorporating attractive short-ranged interactions between parallel sections of walk is derived using numerical transfer matrix techniques. The model displays a collapse ... More
Band alignment and directional stability in abrupt and polar-compensated Si/ZnS interface calculationsMar 20 2014Oct 09 2014We perform a first principles investigation of Si/ZnS interface properties for the [111], [100], and [110] directions, including single-substitution polar-compensated interfaces. The asymmetry of general interface directions poses known challenges for ... More
On the stability of the generalized, finite deformation correspondence model of peridynamicsMar 05 2019A class of peridynamic material models known as constitutive correspondence models provide a bridge between classical continuum mechanics and peridynamics. These models are useful because they allow well-established local constitutive theories to be used ... More
Structured Shrinkage PriorsFeb 13 2019In many regression settings the unknown coefficients may have some known structure, for instance they may be ordered in space or correspond to a vectorized matrix or tensor. At the same time, the unknown coefficients may be sparse, with many nearly or ... More
Spin lattices with two-body Hamiltonians for which the ground state encodes a cluster stateMay 19 2008Jan 05 2009We present a general procedure for constructing lattices of qubits with a Hamiltonian composed of nearest-neighbour two-body interactions such that the ground state encodes a cluster state. We give specific details for lattices in one-, two-, and three-dimensions, ... More
Damped Bogoliubov excitations of a condensate interacting with a static thermal cloudSep 01 2000Oct 25 2000We calculate the damping of condensate collective excitations at finite temperatures arising from the lack of equilibrium between the condensate and thermal atoms. We neglect the non-condensate dynamics by fixing the thermal cloud in static equilibrium. ... More
Clustering Drives Assortativity and Community Structure in Ensembles of NetworksDec 10 2010Jan 05 2011Clustering, assortativity, and communities are key features of complex networks. We probe dependencies between these attributes and find that ensembles with strong clustering display both high assortativity by degree and prominent community structure, ... More
Link and subgraph likelihoods in random undirected networks with fixed and partially fixed degree sequenceOct 16 2006Jun 17 2007The simplest null models for networks, used to distinguish significant features of a particular network from {\it a priori} expected features, are random ensembles with the degree sequence fixed by the specific network of interest. These "fixed degree ... More
Example Data Sets and Collections for BeSpaceD ExplainedAug 01 2016In this report, we present example data sets and collections for the BeSpaceD platform. BeSpaceD is a spatio-temporal modelling and reasoning software framework. We describe the content of a number of the data sets and how the data was obtained. We also ... More
Bethe approximation for the hydrogen-bonding self-avoiding walk in a solventJan 24 2008May 21 2008A square-lattice model for the formation of secondary structures in proteins, the hydrogen-bonding model, extended to include the effects of solvent quality, is examined in the framework of the Bethe approximation.
Corner transfer matrix renormalization group method for two-dimensional self-avoiding walks and other O(n) modelsOct 24 2002Mar 12 2003We present an extension of the corner transfer matrix renormalisation group (CTMRG) method to O(n) invariant models, with particular interest in the self-avoiding walk class of models (O(n=0)). The method is illustrated using an interacting self-avoiding ... More
Scattering of Nucleons in the Classical Skyrme ModelMay 26 2015Jun 12 2015Classically spinning B=1 Skyrmions can be regarded as approximations to nucleons with quantised spin. Here, we investigate nucleon-nucleon scattering through numerical collisions of spinning Skyrmions. We identify the dineutron/diproton and dibaryon short-lived ... More
Contextual bandits with surrogate losses: Margin bounds and efficient algorithmsJun 28 2018Nov 04 2018We use surrogate losses to obtain several new regret bounds and new algorithms for contextual bandit learning. Using the ramp loss, we derive new margin-based regret bounds in terms of standard sequential complexity measures of a benchmark class of real-valued ... More
Post-Newtonian parameters and constraints on Einstein-aether theorySep 20 2005Feb 08 2006We analyze the observational and theoretical constraints on ``Einstein-aether theory", a generally covariant theory of gravity coupled to a dynamical, unit, timelike vector field that breaks local Lorentz symmetry. The results of a computation of the ... More
Physics With Two Time DimensionsJan 14 2010Jan 25 2010We explore the properties of physical theories in space-times with two time dimensions. We show that the common arguments used to rule such theories out do not apply if the dynamics associated with the additional time dimension is thermal or chaotic and ... More
Operators for Space and Time in BeSpaceDFeb 29 2016Mar 31 2016In this report, we present some spatio-temporal operators for our BeSpaceD framework. We port operators known from functional programming languages such as filtering, folding and normalization on abstract data structures to the BeSpaceD specification ... More
Orthogonal Statistical LearningJan 25 2019We provide excess risk guarantees for statistical learning in the presence of an unknown nuisance component. We analyze a two-stage sample splitting meta-algorithm that takes as input two arbitrary estimation algorithms: one for the target model and one ... More
Orthogonal Statistical LearningJan 25 2019Mar 11 2019We provide excess risk guarantees for statistical learning in a setting where the population risk with respect to which we evaluate the target model depends on an unknown model that must be to be estimated from data (a "nuisance model"). We analyze a ... More
Translocation of short and long polymers through an interacting poreFeb 12 2013We perform two-dimensional Langevin dynamics simulations of electric-field driven polymer translocation through an attractive nanopore. We investigate the effect of the location of the attractive region using different pore patterns. This is found to ... More
Spectroscopic probes of isolated nonequilibrium quantum matter: Quantum quenches, Floquet states, and distribution functionsJun 18 2015Nov 20 2015We investigate radio-frequency (rf) spectroscopy, metal-to-superconductor tunneling, and ARPES as probes of isolated out-of-equilibrium quantum systems, and examine the crucial role played by the nonequilibrium distribution function. As an example, we ... More
Necessary conditions for Schur-maximalityNov 27 2017May 08 2018McNamara and Pylyavskyy conjectured precisely which connected skew shapes are maximal in the Schur-positivity order, which says that $B\leq _s A$ if $s_A-s_B$ is Schur-positive. Towards this, McNamara and van Willigenburg proved that it suffices to study ... More
A new class of half-metallic ferromagnets from first principlesNov 28 2016Half-metallic ferromagnetism (HMFM) occurs rarely in materials and yet offers great potential for spintronic devices. Recent experiments suggest a class of compounds with the `ThCr$_{2}$Si$_{2}$' (122) structure -- isostructural and containing elements ... More
On p-adic modular forms and the Bloch-Okounkov theoremSep 23 2015Nov 13 2015Bloch-Okounkov studied certain functions on partitions $f$ called shifted symmetric polynomials. They showed that certain $q$-series arising from these functions (the so-called \emph{$q$-brackets} $\left<f\right>_q$) are quasimodular forms. We revisit ... More
SPS: A software simulator for the Herschel-SPIRE photometerJun 17 2009Instrument simulators are becoming ever more useful for planning and analysing large astronomy survey data. In this paper we present a simulator for the Herschel-SPIRE photometer. We describe the models it uses and the form of the input and output data. ... More
Monte Carlo Simulations with Indefinite and Complex-Valued MeasuresDec 01 1993A method is presented to tackle the sign problem in the simulations of systems having indefinite or complex-valued measures. In general, this new approach is shown to yield statistical errors smaller than the crude Monte Carlo using absolute values of ... More